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FEATURES
LTC4080X 500mA Standalone Li-Ion Charger with Integrated 300mA Synchronous Buck in 3mm x 3mm DFN DESCRIPTIO
The LTC4080X is a complete constant-current/constantvoltage linear battery charger for a single-cell 4.2V lithium-ion/polymer battery with an integrated 300mA synchronous buck converter. A 3mm x 3mm DFN package and low external component count make the LTC4080X especially suitable for portable applications. Furthermore, the LTC4080X is specifically designed to work within USB power specifications. The C H RG pin indicates when charge current has dropped to ten percent of its programmed value (C/10). An internal 4.5 hour timer terminates the charge cycle. The full-featured LTC4080X battery charger also includes automatic recharge and soft-start to limit inrush current. If trickle charging is desired, please see the LTC4080 datasheet. The LTC4080X integrates a synchronous buck converter that is powered from the BAT pin. It has an adjustable output voltage and can deliver up to 300mA of load current. The buck converter also features low-current highefficiency Burst Mode operation that can be selected by the MODE pin. The LTC4080X is available in 10-lead, low profile (0.75 mm) 3mm x 3mm DFN and 10-lead MSE packages.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. Burst Mode is a registered trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents, including 6522118.
Complete Linear Battery Charger with Integrated Buck Converter in 3mm x 3mm DFN Package Battery Charger: Constant-Current/Constant-Voltage Operation with Thermal Feedback to Maximize Charge Rate Without Risk of Overheating Internal 4.5 Hour Safety Timer for Termination Charge Current Programmable Up to 500mA with 5% Accuracy C/10 Charge Current Detection Output 5A Supply Current in Shutdown Mode Switching Regulator: High Efficiency Synchronous Buck Converter 300mA Output Current (Constant-Frequency Mode) 2.7V to 4.5V Input Range (Powered from BAT Pin) 0.8V to V BAT Output Range MODE Pin Selects Fixed (2.25MHz) Constant-Frequency PWM Mode or Low ICC (23A) Burst Mode(R) Operation 2A BAT Current in Shutdown Mode
APPLICATIO S

Wireless Headsets Bluetooth Applications Portable MP3 Players Multifunction Wristwatches
TYPICAL APPLICATIO
VCC (3.75V to 5.5V) VCC LTC4080X EN_CHRG 4.7F EN_BUCK SW FB BAT
Li-Ion Battery Charger with 1.8V Buck Regulator
500mA
100 EFFICIENCY (Burst) EFFICIENCY (PWM)
80 EFFICIENCY (%)
1OH
4.7F
+
4.2V Li-Ion/ POLYMER BATTERY
60
10pF
1M VOUT (1.8V/300mA)
40
MODE GND PROG 806 806k
4080X TA01a
20
COUT 4.7F
U
U
U
Buck Efficiency vs Load Current (VOUT = 1.8V)
1000
100 POWER LOSS (mW) POWER LOSS 10 (PWM) 1
POWER LOSS (Burst)
0 0.01
VBAT = 3.8V 0.1 VOUT = 1.8V L = 10H C = 4.7F 0.01 0.1 1 10 100 1000 LOAD CURRENT (mA) 4080X TA01b
4080Xf
1
LTC4080X ABSOLUTE
(Note 1)
AXI U RATI GS
BAT Short-Circuit Duration............................Continuous BAT Pin Current ...................................................800mA PROG Pin Current ....................................................2mA Junction Temperature .......................................... .125C Operating Temperature Range (Note 2) .. - 40C to 85C Storage Temperature Range.................. - 65C to 125C
VCC , t < 1ms and Duty Cycle < 1% .............. - 0.3V to 7V VCC Steady State ......................................... - 0.3V to 6V BAT, CHRG .................................................. - 0.3V to 6V EN_CHRG, PROG, ACPR .................- 0.3V to VCC + 0.3V MODE, EN_BUCK .......................... - 0.3V to VBAT + 0.3V FB ............................................................... - 0.3V to 2V
PIN CONFIGURATION
TOP VIEW BAT VCC EN_CHRG PROG ACPR 1 2 3 4 5 11 10 SW 9 EN_BUCK 8 MODE 7 FB 6 CHRG TOP VIEW BAT VCC EN_CHRG PROG ACPR 1 2 3 4 5 10 9 8 7 6 SW EN_BUCK MODE FB CHRG
DD PACKAGE 10-LEAD (3mm x 3mm) PLASTIC DFN TJMAX = 110C, JA = 43C/W (NOTE 3) EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH LTC4080XEDD#PBF LTC4080XEMSE#PBF TAPE AND REEL LTC4080XEDD#TRPBF LTC4080XEMSE#TRPBF PART MARKING LCVV LTCVW PACKAGE DESCRIPTION 10-Lead (3mm x 3mm) DFN 10-Lead Plastic MSE TEMPERATURE RANGE 0C to 70C 0C to 70C
Consult LTC Marketing for parts specified with wider operating temperature ranges. Consult LTC Marketing for information on non-standard lead based finish parts. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
2
U
WW
W
11
MSE PACKAGE 10-LEAD PLASTIC MSOP TJMAX = 125C, JA = 40C/W EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
4080Xf
LTC4080X ELECTRICAL CHARACTERISTICS
SYMBOL VCC VBAT ICC ICC_SD PARAMETER Battery Charger Supply Voltage Input Voltage for the Switching Regulator
The denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C, VCC = 5V, VBAT = 3.8V, VEN_CHRG = 0V, VEN_BUCK = VBAT, VMODE = 0V. (Note 2)
CONDITIONS (Note 4) (Note 5)

MIN 3.75 2.7
TYP 5 3.8 110 5 2 0.6 2
MAX 5.5 4.5 300 10
UNITS V V A A A A A
Quiescent Supply Current (Charger On, VBAT = 4.5V (Forces IBAT and IPROG = 0), Switching Regulator Off) VEN_BUCK = 0 Supply Current in Shutdown (Both VEN_CHRG = 5V, VEN_BUCK = 0, VCC > VBAT Battery Charger and Switching VEN_CHRG = 4V, VEN_BUCK = 0, VCC (3.5V) < Regulator Off) VBAT (4V) Battery Current in Shutdown (Both Battery Charger and Switching Regulator Off) VBAT Regulated Output Voltage Current Mode Charge Current VCC Undervoltage Lockout Voltage PROG Pin Servo Voltage VEN_CHRG = 5V, VEN_BUCK = 0, VCC > VBAT VEN_CHRG = 4V, VEN_BUCK = 0, VCC (3.5V) < VBAT (4V) IBAT = 2mA IBAT = 2mA, 4.3V < VCC < 5.5V RPROG = 4k; Current Mode; VEN_BUCK = 0 RPROG = 0.8k; Current Mode; VEN_BUCK = 0 VCC Rising VCC Falling 0.8k RPROG 4k
IBAT_SD
5
Battery Charger VFLOAT IBAT VUVLO_CHRG VPROG VASD tSS_CHRG VBADBAT VRECHRG VUVCL1, VUVCL2 tTIMER

4.179 4.158 90 475 3.5 2.8 0.98 60 15
4.2 4.2 100 500 3.6 3.0 1.0 82 32 180 2.9
4.221 4.242 110 525 3.7 3.2 1.02 100 45
V V mA mA V V V mV mV s V
Automatic Shutdown Threshold Voltage (VCC - VBAT), VCC Low to High (VCC - VBAT), VCC High to Low Battery Charger Soft-Start Time Bad Battery Threshold Voltage Recharge Battery Threshold Voltage (VCC - VBAT) Undervoltage Current Limit Threshold Voltage Charge Termination Timer Recharge Time Low-Battery Charge Time VBAT = 2.5V RPROG = 2k (Note 6) VFLOAT - VBAT, 0C < TA < 85C IBAT = 0.9 ICHG IBAT = 0.1 ICHG

70 180 90 3 1.5 0.75 0.085
100 300 130 4.5 2.25 1.125 0.1 115 750 2 75
130
mV mV mV
6 3 1.5 0.115
hrs hrs hrs mA/mA C m Hz %
IC/10 TLIM RON_CHRG fBADBAT DBADBAT Buck Converter VFB IFB fOSC IBAT_NL_CF
End of Charge Indication Current Level Junction Temperature in ConstantTemperature Mode
IBAT = 350mA, VCC = 4V Power FET On-Resistance (Between VCC and BAT) Defective Battery Detection CHRG Pulse VBAT = 2V Frequency Defective Battery Detection CHRG Pulse VBAT = 2V Frequency Duty Ratio FB Servo Voltage FB Pin Input Current Switching Frequency No-Load Battery Current (Continuous Frequency Mode) No-Load for Regulator, VEN_CHRG = 5V, L = 10H, C = 4.7F VFB = 0.85V

0.78 -50 1.8
0.80 2.25 1.9
0.82 50 2.75
V nA MHz mA
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LTC4080X ELECTRICAL CHARACTERISTICS
SYMBOL IBAT_NL_BM IBAT_SLP VUVLO_BUCK RON_P RON_N ILIM_P ILIM_N IZERO_CF IPEAK IZERO_BM tSS_BUCK Logic VIH VIL VOL IIH IIL REN_CHRG ICHRG IACPR Input High Voltage Input Low Voltage Output Low Voltage (CHRG, ACPR) Input Current High Input Current Low EN_CHRG Pin Input Resistance CHRG Pin Leakage Current ACPR Pin Leakage Current EN_CHRG, EN_BUCK, MODE Pin Low to High EN_CHRG, EN_BUCK, MODE Pin High to Low ISINK = 5mA EN_BUCK, MODE Pins at 5.5V, VBAT = 5V EN_CHRG, EN_BUCK, MODE Pins at GND VEN_CHRG = 5V VBAT = 4.5V, VCHRG = 5V VCC = 3V, VCHRG = 5V

The denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C, VCC = 5V, VBAT = 3.8V, VEN_CHRG = 0V, VEN_BUCK = VBAT, VMODE = 0V. (Note 2)
PARAMETER No-Load Battery Current (Burst Mode Operation) Battery Current in SLEEP Mode Buck Undervoltage Lockout Voltage PMOS Switch On-Resistance NMOS Switch On-Resistance PMOS Switch Current Limit NMOS Switch Current Limit NMOS Zero Current in Normal Mode Peak Current in Burst Mode Operation Zero Current in Burst Mode Operation Buck Soft-Start Time MODE = VBAT MODE = VBAT From the Rising Edge of EN_BUCK to 90% of Buck Regulated Output 50 20 375 CONDITIONS No-Load for Regulator, VEN_CHRG = 5V, MODE = VBAT, L = 10H, C = 4.7F VEN_CHRG = 5V, MODE = VBAT, VOUT > Regulation Voltage VBAT Rising VBAT Falling

MIN
TYP 23
MAX
UNITS A
10 2.6 2.4
15 2.7 2.5 0.95 0.85 520 700 15 100 35 400
20 2.8 2.6
A V V
700
mA mA mA
150 50
mA mA s
1.2 0.4 60 -1 -1 1 1.45 105 1 1 3.3 1 1
V V mV A A M A A
Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: The LTC4080X is guaranteed to meet performance specifications from 0C to 85C. Specifications over the -40C to 85C operating temperature range are assured by design, characterization and correlation with statistical process controls. Note 3: Failure to solder the exposed backside of the package to the PC board ground plane will result in a thermal resistance much higher than 43C/W.
Note 4: Although the LTC4080X charger functions properly at 3.75V, full charge current requires an input voltage greater than the desired final battery voltage per VUVCL1 specification. Note 5: The 2.8V maximum buck undervoltage lockout (VUVLO_BUCK) exit threshold must first be exceeded before the minimum VBAT specification applies. Note 6: IC/10 is expressed as a fraction of measured full charge current with indicated PROG resistor.
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LTC4080X TYPICAL PERFORMANCE CHARACTERISTICS
specified) Battery Regulation (Float) Voltage vs Charge Current
4.21 4.20 FLOAT VOLTAGE (V) 4.19 FLOAT VOLTAGE (V) 4.18 4.17 4.16 4.15 4.14 4.13 0 50 200 150 100 CHARGE CURRENT (mA) 250
4080X G01
(TA = 25C, VCC = 5V, VBAT = 3.8V, unless otherwise Battery Regulation (Float) Voltage vs VCC Supply Voltage
4.25 4.20 4.15 FLOAT VOLTAGE (V) 4.10 4.05 4.00 3.95 3.90 3.85
Battery Regulation (Float) Voltage vs Temperature
4.210 4.205 4.200 4.195 4.190 4.185 4.180 4.175 4.170 4.165 4.160 - 50 - 30 - 10 50 30 10 TEMPERATURE (C) 70 90
RPROG = 2k
4
4.5
5 5.5 VCC SUPPLY VOLTAGE (V)
6
4080X G03
4080X G02
Charge Current vs Temperature with Thermal Regulation (Constant-Current Mode)
250 VCC = 6V VBAT = 3V RPROG = 2k 1.0
PROG Pin Voltage vs Charge Current
0.9 RPROG = 2k 0.8
Charger FET On-Resistance vs Temperature
VCC = 4V 0.8 IBAT = 350mA 0.7 0.6 RDS(ON) ()
200 CHARGE CURRENT (mA)
THERMAL CONTROL LOOP IN OPERATION
VPROG (V)
150
0.6
0.5 0.4 0.3
100
0.4
50
0.2
0.2 0.1
0 -50
-25
0
25
50
75
100
125
0
0
25
TEMPERATURE (C)
4080X G04
50 75 100 125 150 175 200 CHARGE CURRENT (mA)
4080X G05
0 - 50 - 30
-10
30 50 10 TEMPERATURE (C)
70
90
4080X G06
EN_CHRG, EN_BUCK and MODE Pin Threshold Voltage vs Temperature
0.95 0.90 THRESHOLD VOLTAGE (V) 0.85 0.80 0.75 0.70 0.65 0.60 0.55 0.50 -50 -30 -10 10 30 50 TEMPERATURE (C) 70 90
4080X G07
EN_CHRG Pin Pulldown Resistance vs Temperature
1.7 1.6 1.5 1.4 1.3 1.2 1.1 1.0 -50
FALLING
PULLDOWN RESISTANCE (M)
RISING
-30
-10 10 30 50 TEMPERATURE (C)
70
90
4080X G08
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LTC4080X TYPICAL PERFORMANCE CHARACTERISTICS
specified) CHRG and ACPR Pin Output Low Voltage vs Temperature
80 ICHRG, IACPR = 5mA 70 60 VOLTAGE (mV) 50 40 30 20 10 0 -50 -30 -10 10 30 50 TEMPERATURE (C) 90
4080X G09
(TA = 25C, VCC = 5V, VBAT = 3.8V, unless otherwise Buck Oscillator Frequency vs Battery Voltage
2.28 2.27 FREQUENCY (MHz) 2.26 2.25 2.24 2.23 2.22 2.5
Normalized Charge Termination Time vs Temperature
1.05
NORMALIZED TIMER PERIOD
1.00
0.95
0.90
0.85
70
0.80 -50
-30
-10
10
30
50
70
90
4080X G10
3.0
TEMPERATURE (C)
3.5 4.0 BATTERY VOLTAGE (V)
4.5
4080X G11
Buck Oscillator Frequency vs Temperature
2.4 VBAT = 3.8V 2.3 FREQUENCY (MHz) 2.2 VBAT = 2.7V 2.1 2.0 1.9 1.8 -60 -40 -20 0 20 40 60 TEMPERATURE (C) VBAT = 4.5V EFFICIENCY (%) 80 100
Buck Efficiency vs Load Current (VOUT = 1.8V)
1000 EFFICIENCY (Burst) EFFICIENCY (PWM) 100
Buck Efficiency vs Load Current (VOUT = 1.5V)
1000 EFFICIENCY (Burst) EFFICIENCY (PWM)
100 POWER LOSS (mW) EFFICIENCY (%) POWER LOSS 10 (PWM)
80
100 POWER LOSS (mW) POWER LOSS 10 (PWM)
60
60
40
20
80
100
0 0.01
1 POWER LOSS (Burst) VBAT = 3.8V 0.1 VOUT = 1.8V L = 10H C = 4.7F 0.01 0.1 1 10 100 1000 LOAD CURRENT (mA)
4080X G13
40
20
0 0.01
1 POWER LOSS (Burst) VBAT = 3.8V 0.1 VOUT = 1.5V L = 10H C = 4.7F 0.01 0.1 1 10 100 1000 LOAD CURRENT (mA) 4080X G13a
4080X G12
Buck Output Voltage vs Battery Voltage
1.810 1.805 BUCK OUTPUT VOLTAGE (V) 1.800 1.795 1.790 1.785 1.780 2.5 IOUT = 1mA VOUT SET FOR 1.8V 1.810 Burst Mode OPERATION BUCK OUTPUT VOLTAGE (V) PWM MODE 1.805
Buck Output Voltage vs Temperature
35 IOUT = 1mA VOUT SET FOR 1.8V Burst Mode OPERATION PWM MODE 1.800 1.795 1.790 1.785 1.780 -50 -30 BUCK INPUT CURRENT (A) 30 25 20 15 10 5
No-Load Buck Input Current (Burst Mode Operation) vs Battery Voltage
IOUT = 1mA VOUT = 1.8V L = 10H
3.0 3.5 4.0 BATTERY VOLTAGE (V)
4.5
4080X G14
30 50 -10 10 TEMPERATURE (C)
70
90
4080X G15
0 2.5
3.5 3.0 4.0 BATTERY VOLTAGE (V)
4.5
4080X G17
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LTC4080X TYPICAL PERFORMANCE CHARACTERISTICS
specified) No-Load Buck Input Current (Burst Mode Operation) vs Temperature
35 NO LOAD INPUT CURRENT (A) 30 25 20 15 10 5 0 -50 -30 1.2 L = 10H C = 4.7F VOUT = 1.8V VBAT = 4.2V 1.0 ON-RESISTANCE () 0.8 0.6 0.4 0.2 0 2.5 ON-RESISTANCE () VBAT = 3.8V 1.0 0.8 0.6 0.4 0.2 0 -50 -30
(TA = 25C, VCC = 5V, VBAT = 3.8V, unless otherwise Buck Main Switch (PMOS) On-Resistance vs Temperature
1.2
Buck Main Switch (PMOS) On-Resistance vs Battery Voltage
VBAT = 2.7V
30 50 -10 10 TEMPERATURE (C)
70
90
4080X G18
3.0
4.5 4.0 BATTERY VOLTAGE (V)
3.5
5.0
4080X G19
30 50 -10 10 TEMPERATURE (C)
70
90
4080X G20
Buck Synchronous Switch (NMOS) On-Resistance vs Battery Voltage
1.2 1.0 ON-RESISTANCE () 0.8 0.6 0.4 0.2 0 2.5 ON-RESISTANCE () 1.2 1.0 0.8 0.6 0.4 0.2
Buck Synchronous Switch (NMOS) On-Resistance vs Temperature
3.0
4.5 4.0 BATTERY VOLTAGE (V)
3.5
5.0
4080X G21
0 -50 -30
30 50 -10 10 TEMPERATURE (C)
70
90
4080X G22
Maximum Output Current (PWM Mode) vs Battery Voltage
500 MAXIMUM OUTPUT CURRENT (mA) L = 10H MAXIMUM OUTPUT CURRENT (mA) VOUT SET FOR 1.8V 400 80 70 60 50 40 30 20 10
Maximum Output Current (Burst Mode Operation) vs Battery Voltage
L = 10H
VOUT SET FOR 1.8V
300
200
100 2.7
3
3.3
3.6
3.9
4.2
4.5
0 2.7
3
3.3
3.6
3.9
4.2
4.5
4080X G24
BATTERY VOLTAGE (V)
4080X G23
BATTERY VOLTAGE (V)
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LTC4080X TYPICAL PERFORMANCE CHARACTERISTICS
specified) Output Voltage Transient Step Response (PWM Mode) Output Voltage Waveform when Switching Between Burst and PWM Mode (ILOAD = 10mA) Output Voltage Transient Step Response (Burst Mode) (TA = 25C, VCC = 5V, VBAT = 3.8V, unless otherwise
VOUT 20mV/DIV AC COUPLED ILOAD 250mA/DIV I=0
4080X G25
VOUT 50mV/DIV AC COUPLED
VOUT 20mV/DIV AC COUPLED ILOAD 50mA/DIV I=0 50s/DIV
4080X G27 4080X G26
VMODE 5V/DIV 0V 50s/DIV
50s/DIV
Buck VOUT Soft-Start (ILOAD = 50mA)
Charger VPROG Soft-Start
VOUT 1V/DIV 0V VEN_BUCK 5V/DIV 0V
4080X G28
VPROG 200mV/DIV V=0
4080X G29
200s/DIV
50s/DIV
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LTC4080X PI FU CTIO S
BAT (Pin 1): Charge Current Output and Buck Regulator Input. Provides charge current to the battery and regulates the final float voltage to 4.2V. An internal precision resistor divider from this pin sets the float voltage and is disconnected in charger shutdown mode. This pin must be decoupled with a low ESR capacitor for low-noise buck operation. VCC (Pin 2): Positive Input Supply Voltage. This pin provides power to the battery charger. VCC can range from 3.75V to 5.5V. This pin should be bypassed with at least a 1F capacitor. When VCC is less than 32mV above the BAT pin voltage, the battery charger enters shutdown mode. EN_CHRG (Pin 3): Enable Input Pin for the Battery Charger. Pulling this pin above the manual shutdown threshold (VIH) puts the LTC4080X charger in shutdown mode, thus stopping the charge cycle. In battery charger shutdown mode, the LTC4080X has less than 10A supply current and less than 5A battery drain current provided the regulator is not running. Enable is the default state, but the pin should be tied to GND if unused. PROG (Pin 4): Charge Current Program and Charge Current Monitor Pin. Connecting a 1% resistor, RPROG, to ground programs the charge current. When charging in constant-current mode, this pin servos to 1V. In all modes, the voltage on this pin can be used to measure the charge current using the following formula: I BAT V = PROG * 40 0 RPROG pin will be pulled to ground; otherwise the pin is high impedance. CHRG (Pin 6): Open-Drain Charge Status Output. The charge status indicator pin has three states: pulldown, high impedance state, and pulsing at 2Hz. This output can be used as a logic interface or as an LED driver. When the battery is being charged, the CHRG pin is pulled low by an internal N-channel MOSFET. When the charge current drops to 10% of the full-scale current, the CHRG pin is forced to a high impedance state. When the battery voltage remains below 2.9V for one quarter of the full charge time, the battery is considered defective, and the CHRG pin pulses at a frequency of 2Hz with 75% duty cycle. FB (Pin 7): Feedback Pin for the Buck Regulator. A resistor divider from the regulator's output to the FB pin programs the output voltage. Servo value for this pin is 0.8V. MODE (Pin 8): Burst Mode Enable Pin. Tie this pin high to force the LTC4080X regulator into Burst Mode operation for all load conditions. Tie this pin low to force constantfrequency mode operation for all load conditions. Do not float this pin. EN_BUCK (Pin 9): Enable Input Pin for the Buck Regulator. Pull this pin high to enable the regulator, pull low to shut down. Do not float this pin. SW (Pin 10): Switch Pin for the Buck Regulator. Minimize the length of the metal trace connected to this pin. Place the inductor as close to this pin as possible. GND (Pin 11): Ground. This pin is the back of the Exposed Pad package and must be soldered to the PCB for electrical connection and rated thermal performance.
ACPR (Pin 5): Open-Drain Power Supply Status Output. When VCC is greater than the undervoltage lockout threshold (3.6V) and greater than VBAT + 82mV, the ACPR
U
U
U
4080Xf
9
LTC4080X BLOCK DIAGRA W
2 VCC CHARGER SHUTDOWN MP3 X1 D1 PROG 0.1V 1 MP1 X400 D2 D3 TA
3 EN_CHRG 0.82V REN
6 CHRG 1V
MP4 1.22V R2 PULSE LOGIC 2.9V CHARGER ENABLE
C2 BAT 4 PROG RPROG
BADBAT
+
C4 5 ACPR
VCC CHARGER OSCILLATOR COUNTER
-
3.6V
+
C5
-
VBAT + 82mV LINEAR BATTERY CHARGER
9 EN_BUCK 0.82V
SYNCHRONOUS BUCK CONVERTER C6 ENABLE BUCK PWM CONTROL AND DRIVE L1 10 SW MN1 CPL R7 VOUT
8 MODE 0.82V
C7
11 GND
Figure 1. LTC4080X Block Diagram
10
+
2.25MHz BUCK OSCILLATOR
ERROR AMP 0.8V
-
-
+
+
-
- +
C1 CA
+
C3
- +
115C
TDIE
-
-
MA
+
R1 VA
BAT
-
-
+
+
-
+
CHARGE CONTROL LOGIC MP2 7 FB R8 COUT
4080X BD
4080Xf
LTC4080X OPERATIO
The LTC4080X is a full-featured linear battery charger with an integrated synchronous buck converter designed primarily for handheld applications. The battery charger is capable of charging single-cell 4.2V Li-Ion batteries. The buck converter is powered from the BAT pin and has a programmable output voltage providing a maximum load current of 300mA. The converter and the battery charger can run simultaneously or independently of each other. BATTERY CHARGER OPERATION Featuring an internal P-channel power MOSFET, MP1, the battery charger uses a constant-current/constant-voltage charge algorithm with programmable current. Charge current can be programmed up to 500mA with a final float voltage of 4.2V 0.5%. The CHRG open-drain status output indicates when C/10 has been reached. No blocking diode or external sense resistor is required; thus, the basic charger circuit requires only two external components. The ACPR open-drain output indicates if the VCC input voltage, and the difference between VCC and BAT, are sufficient for charging. An internal charge termination timer adheres to battery manufacturer safety guidelines. Furthermore, the LTC4080X battery charger is capable of operating from a USB power source. A charge cycle begins when the voltage at the VCC pin rises above 3.6V and approximately 82mV above the BAT pin voltage, a 1% program resistor is connected from the PROG pin to ground, and the EN_CHRG pin is pulled below the shutdown threshold (VIL). When the BAT pin approaches the final float voltage of 4.2V, the battery charger enters constant-voltage mode and the charge current begins to decrease. When the current drops to 10% of the full-scale charge current, an internal comparator turns off the N-channel MOSFET driving the CHRG pin, and the pin becomes high impedance. An internal thermal limit reduces the programmed charge current if the die temperature attempts to rise above a preset value of approximately 115C. This feature protects the LTC4080X from excessive temperature and allows the user to push the limits of the power handling capability of a given circuit board without the risk of damaging the LTC4080X or external components. Another benefit of the
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thermal limit is that charge current can be set according to typical, rather than worst-case, ambient temperatures for a given application with the assurance that the battery charger will automatically reduce the current in worst-case conditions. An internal timer sets the total charge time, tTIMER (typically 4.5 hours). When this time elapses, the charge cycle terminates and the CHRG pin assumes a high impedance state even if C/10 has not yet been reached. To restart the charge cycle, remove the input voltage and reapply it or momentarily force the EN_CHRG pin above VIH. A new charge cycle will automatically restart if the BAT pin voltage falls below VRECHRG (typically 4.1V). Constant-Current / Constant-Voltage / Constant-Temperature The LTC4080X battery charger uses a unique architecture to charge a battery in a constant-current, constant-voltage and constant-temperature fashion. Figure 1 shows a Simplified Block Diagram of the LTC4080X. Three of the amplifier feedback loops shown control the constant-current, CA, constant-voltage, VA, and constant-temperature, TA modes. A fourth amplifier feedback loop, MA, is used to increase the output impedance of the current source pair, MP1 and MP3 (note that MP1 is the internal P-channel power MOSFET). It ensures that the drain current of MP1 is exactly 400 times the drain current of MP3. Amplifiers CA and VA are used in separate feedback loops to force the charger into constant-current or constantvoltage mode, respectively. Diodes D1 and D2 provide priority to either the constant-current or constant-voltage loop, whichever is trying to reduce the charge current the most. The output of the other amplifier saturates low which effectively removes its loop from the system. When in constant-current mode, CA servos the voltage at the PROG pin to be precisely 1V. VA servos its non-inverting input to 1.22V when in constant-voltage mode and the internal resistor divider made up of R1 and R2 ensures that the battery voltage is maintained at 4.2V. The PROG pin voltage gives an indication of the charge current anytime in the charge cycle, as discussed in "Programming Charge Current" in the Applications Information section.
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LTC4080X OPERATIO
If the die temperature starts to creep up above 115C due to internal power dissipation, the transconductance amplifier, TA, limits the die temperature to approximately 115C by reducing the charge current. Diode D3 ensures that TA does not affect the charge current when the die temperature is below 115C. In thermal regulation, the PROG pin voltage continues to give an indication of the charge current. In typical operation, the charge cycle begins in constantcurrent mode with the current delivered to the battery equal to 400V/RPROG. If the power dissipation of the LTC4080X results in the junction temperature approaching 115C, the amplifier (TA) will begin decreasing the charge current to limit the die temperature to approximately 115C. As the battery voltage rises, the LTC4080X either returns to full constant-current mode or enters constant-voltage mode straight from constant-temperature mode. Battery Charger Undervoltage Lockout (UVLO) An internal undervoltage lockout circuit monitors the VCC input voltage and keeps the battery charger off until VCC rises above 3.6V and approximately 82mV above the BAT pin voltage. The 3.6V UVLO circuit has a built-in hysteresis of approximately 0.6V, and the 82mV automatic shutdown threshold has a built-in hysteresis of approximately 50mV. During undervoltage lockout conditions, maximum battery drain current is 5A and maximum supply current is 10A. Undervoltage Charge Current Limiting (UVCL) The battery charger in the LTC4080X includes undervoltage charge current limiting that prevents full charge current until the input supply voltage reaches approximately 300mV above the battery voltage (VUVCL1). This feature is particularly useful if the LTC4080X is powered from a supply with long leads (or any relatively high output impedance). See Applications Information section for further details. Defective Battery Detection At the beginning of a charge cycle, if the battery voltage is below 2.9V for one quarter of the total charge time (1.125 hr), the battery is assumed to be defective, the charge cycle terminates and the CHRG output pulses at a frequency of 2Hz with a 75% duty cycle. If, for any reason, the battery voltage rises above 2.9V, the charge cycle will
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be restarted. To restart the charge cycle (i.e., when the dead battery is replaced with a discharged battery less than 2.9V), the charger must be reset by removing the input voltage and reapplying it or temporarily pulling the EN_CHRG pin above the shutdown threshold. Battery Charger Shutdown Mode The LTC4080X's battery charger can be disabled by pulling the EN_CHRG pin above the shutdown threshold (VIH). In shutdown mode, the battery drain current is reduced to about 2A and the VCC supply current to about 5A provided the regulator is off. When the input voltage is not present, the battery charger is in shutdown and the battery drain current is less than 5A. Power Supply Status Indicator (ACPR) The power supply status output has two states: pulldown and high impedance. The pulldown state indicates that VCC is above the undervoltage lockout threshold and at least 82mV above the BAT voltage (see Undervoltage Lockout). When these conditions are not met, the ACPR pin is high impedance indicating that the LTC4080X is unable to charge the battery. CHRG Status Output Pin The charge status indicator pin has three states: pulldown, pulsing at 2Hz (see Defective Battery Detection) and high impedance. The pulldown state indicates that the battery charger is in a charge cycle. A high impedance state indicates that the charge current has dropped below 10% of the full-scale current or the battery charger is disabled. When the timer runs out (4.5 hrs), the CHRG pin is also forced to the high impedance state. If the battery charger is not in constant-voltage mode when the charge current is forced to drop below 10% of the full-scale current by UVCL, CHRG will stay in the strong pulldown state. Charge Current Soft-Start The LTC4080X's battery charger includes a soft-start circuit to minimize the inrush current at the start of a charge cycle. When a charge cycle is initiated, the charge current ramps from zero to full-scale current over a period of approximately 180s. This has the effect of minimizing the transient current load on the power supply during start-up.
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LTC4080X OPERATIO
Timer and Recharge The LTC4080X's battery charger has an internal charge termination timer that starts when the input voltage is greater than the undervoltage lockout threshold and at least 82mV above BAT, and the battery charger is leaving shutdown. At power-up or when exiting shutdown, the charge time is set to 4.5 hours. Once the charge cycle terminates, the battery charger continuously monitors the BAT pin voltage using a comparator with a 2ms filter time. When the average battery voltage falls below 4.1V (which corresponds to 80%-90% battery capacity), a new charge cycle is initiated and a 2.25 hour timer begins. This ensures that the battery is kept at, or near, a fully charged condition and eliminates the need for periodic charge cycle initiations. The CHRG output assumes a strong pulldown state during recharge cycles until C/10 is reached or the recharge cycle terminates. SWITCHING REGULATOR OPERATION: The switching buck regulator in the LTC4080X can be turned on by pulling the EN_BUCK pin above VIH. It has two userselectable modes of operation: constant-frequency (PWM) mode and Burst Mode Operation. The constant-frequency mode operation offers low noise at the expense of efficiency whereas the Burst Mode operation offers higher efficiency at light loads at the cost of increased noise, higher output voltage ripple, and less output current. A detailed description of different operating modes and different aspects of operation follow. Operations can best be understood by referring to the Block Diagram. Constant-Frequency (PWM) Mode Operation The switching regulator operates in constant-frequency (PWM) mode when the MODE pin is pulled below VIL . In this mode, it uses a current mode architecture including an oscillator, an error amplifier, and a PWM comparator for excellent line and load regulation. The main switch MP2 (P-channel MOSFET) turns on to charge the inductor at the beginning of each clock cycle if the FB pin voltage is less than the 0.8V reference voltage. The current into the inductor (and the load) increases until it reaches the
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peak current demanded by the error amp. At this point, the main switch turns off and the synchronous switch MN1 (N-channel MOSFET) turns on allowing the inductor current to flow from ground to the load until either the next clock cycle begins or the current reduces to the zero current (IZERO) level. Oscillator: In constant-frequency mode, the switching regulator uses a dedicated oscillator which runs at a fixed frequency of 2.25MHz. This frequency is chosen to minimize possible interference with the AM radio band. Error Amplifier: The error amplifier is an internally compensated transconductance (gm) amplifier with a gm of 65 mhos. The internal 0.8V reference voltage is compared to the voltage at the FB pin to generate a current signal at the output of the error amplifier. This current signal represents the peak inductor current required to achieve regulation. PWM Comparator: Lossless current sensing converts the PMOS switch current signal to a voltage which is summed with the internal slope compensation signal. The PWM comparator compares this summed signal to determine when to turn off the main switch. The switch current sensing is blanked for ~12ns at the beginning of each clock cycle to prevent false switch turn-off. Burst Mode Operation Burst Mode operation can be selected by pulling the MODE pin above VIH. In this mode, the internal oscillator is disabled, the error amplifier is converted into a comparator monitoring the FB voltage, and the inductor current swings between a fixed IPEAK (~100mA) and IZERO (35mA) irrespective of the load current as long as the FB pin voltage is less than or equal to the reference voltage of 0.8V. Once VFB is greater than 0.8V, the control logic shuts off both switches along with most of the circuitry and the regulator is said to enter into SLEEP mode. In SLEEP mode, the regulator only draws about 20A from the BAT pin provided that the battery charger is turned off. When the output voltage droops about 1% from its nominal value, the regulator wakes up and the inductor current resumes swinging between IPEAK and IZERO. The output capacitor recharges and causes the regulator to re-enter the SLEEP state if the output load remains light
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LTC4080X OPERATIO
enough. The frequency of this intermittent burst operation depends on the load current. That is, as the load current drops further, the regulator turns on less frequently. Thus Burst Mode operation increases the efficiency at light loads by minimizing the switching and quiescent losses. However, the output voltage ripple increases to about 2%. To minimize ripple in the output voltage, the current limits for both switches in Burst Mode operation are reduced to about 20% of their values in the constant-frequency mode. Also the zero current of the synchronous switch is changed to about 35mA thereby preventing reverse conduction through the inductor. Consequently, the regulator can only deliver approximately 67mA of load current while in Burst Mode operation. Any attempt to draw more load current will cause the output voltage to drop out of regulation. Current Limit To prevent inductor current runaway, there are absolute current limits (ILIM) on both the PMOS main switch and the NMOS synchronous switch. These limits are internally set at 520mA and 700mA respectively for PWM mode. If the peak inductor current demanded by the error amplifier ever exceeds the PMOS ILIM, the error amplifier will be ignored and the inductor current will be limited to PMOS ILIM. In Burst Mode operation, the PMOS current limit is reduced to 100mA to minimize output voltage ripple. Zero Current Comparator The zero or reverse current comparator monitors the inductor current to the output and shuts off the synchronous rectifier when this current reduces to a predetermined value (IZERO). In fixed frequency mode, this is set to negative 15mA meaning that the regulator allows the inductor current to flow in the reverse direction (from the output to ground through the synchronous rectifier) to a maximum value of 15mA. This is done to ensure that the regulator is able to regulate at very light loads without skipping any cycles thereby keeping output voltage ripple and noise low at the cost of efficiency.
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However, in Burst Mode operation, IZERO is set to positive 35mA meaning that the synchronous switch is turned off as soon as the current through the inductor to the output decreases to 35mA in the discharge cycle. This preserves the charge on the output capacitor and increases the overall efficiency at light loads. Soft-Start The LTC4080X switching regulator provides soft-start in both modes of operation by slowly charging an internal capacitor. The voltage on this capacitor, in turn, slowly ramps the current limits of both switches from a low value to their respective maximum values over a period of about 400s. The soft-start capacitor is discharged completely whenever the regulator is disabled. Short-Circuit Protection In the event of a short circuit at the output or during start-up, VOUT will be near zero volts. Since the downward slope of the inductor current is ~VOUT/L, the inductor current may not get a chance to discharge enough to avoid a runaway situation. Because the current sensing is blanked for ~12ns at the beginning of each clock cycle, inductor current can build up to a dangerously high level over a number of cycles even if there is a hard current limit on the main PMOS switch. This is why the switching regulator in the LTC4080X also monitors current through the synchronous NMOS switch and imposes a hard limit on it. If the inductor current through the NMOS switch at the end of a discharge cycle is not below this limit, the regulator skips the next charging cycle thereby preventing inductor current runaway. Switching Regulator Undervoltage Lockout Whenever VBAT is less than 2.7V, an undervoltage lockout circuit keeps the regulator off, preventing unreliable operation. However, if the regulator is already running and the battery voltage is dropping, the undervoltage comparator does not shut down the regulator until VBAT drops below 2.5V.
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LTC4080X OPERATIO
Dropout Operation When the BAT pin voltage approaches VOUT, the duty cycle of the switching regulator approaches 100%. When VBAT is approximately equal to VOUT, the regulator is said to be in dropout. In dropout, the main switch (MP2) stays on continuously with the output voltage being equal to the battery voltage minus the voltage drops across the main switch and the inductor.
APPLICATIO S I FOR ATIO
BATTERY CHARGER Programming Charge Current
The battery charge current is programmed using a single resistor from the PROG pin to ground. The charge current is 400 times the current out of the PROG pin. The program resistor and the charge current are calculated using the following equations: RPROG = 400 * 1V IBAT , IBAT = 400 * 1V RPROG
The charge current out of the BAT pin can be determined at any time by monitoring the PROG pin voltage and using the following equation: I BAT = VPROG * 400 RPROG
Stability Considerations The LTC4080X battery charger contains two control loops: constant-voltage and constant-current. The constantvoltage loop is stable without any compensation when a battery is connected with low impedance leads. Excessive lead length, however, may add enough series inductance to require a bypass capacitor of at least 1F from BAT to GND. Furthermore, a 4.7F capacitor with a 0.2 to 1 series resistor from BAT to GND is required to keep ripple voltage low when the battery is disconnected. In constant-current mode, the PROG pin voltage is in the feedback loop, not the battery voltage. Because of
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Global Thermal Shutdown The LTC4080X includes a global thermal shutdown which shuts off the entire device (battery charger and switching regulator) if the die temperature exceeds 160C. The LTC4080X resumes normal operation once the temperature drops approximately 14C. the additional pole created by PROG pin capacitance, capacitance on this pin must be kept to a minimum. With no additional capacitance on the PROG pin, the battery charger is stable with program resistor values as high as 25k. However, additional capacitance on this node reduces the maximum allowed program resistor. The pole frequency at the PROG pin should be kept above 100kHz. Therefore, if the PROG pin is loaded with a capacitance, CPROG, the following equation should be used to calculate the maximum resistance value for RPROG: RPROG 1 2 * 100kHz * CPROG Average, rather than instantaneous, battery current may be of interest to the user. For example, when the switching regulator operating in low-current mode is connected in parallel with the battery, the average current being pulled out of the BAT pin is typically of more interest than the instantaneous current pulses. In such a case, a simple RC filter can be used on the PROG pin to measure the average battery current as shown in Figure 2. A 10k resistor has been added between the PROG pin and the filter capacitor to ensure stability.
LTC4080X PROG GND RPROG
4080X F02
10k CFILTER
CHARGE CURRENT MONITOR CIRCUITRY
Figure 2. Isolating Capacitive Load on PROG Pin and Filtering
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LTC4080X APPLICATIO S I FOR ATIO
Undervoltage Charge Current Limiting (UVCL) USB powered systems tend to have highly variable source impedances (due primarily to cable quality and length). A transient load combined with such impedance can easily trip the UVLO threshold and turn the battery charger off unless undervoltage charge current limiting is implemented. Consider a situation where the LTC4080X is operating under normal conditions and the input supply voltage begins to sag (e.g. an external load drags the input supply down). If the input voltage reaches VUVCL (approximately 300mV above the battery voltage, VUVCL), undervoltage charge current limiting will begin to reduce the charge current in an attempt to maintain VUVCL between VCC and BAT. The LTC4080X will continue to operate at the reduced charge current until the input supply voltage is increased or voltage mode reduces the charge current further. Operation from Current Limited Wall Adapter By using a current limited wall adapter as the input supply, the LTC4080X can dissipate significantly less power when programmed for a current higher than the limit of the wall adapter. Consider a situation where an application requires a 200mA charge current for a discharged 800mAh Li-Ion battery. If a typical 5V (non-current limited) input supply is available then the peak power dissipation inside the part can exceed 300mW. Now consider the same scenario, but with a 5V input supply with a 200mA current limit. To take advantage of the supply, it is necessary to program the LTC4080X to charge at a current greater than 200mA. Assume that the LTC4080X charger is programmed for 300mA (i.e., RPROG = 1.33k) to ensure that part tolerances maintain a programmed current higher than 200mA. Since the battery charger will demand a charge current higher than the current limit of the input supply, the supply voltage will collapse to the battery voltage plus 200mA times the on-resistance of the internal PFET. The on-resistance of the battery charger power device is approximately 0.75 with a 5V supply. The actual on-resistance will be slightly higher due to the fact that the input supply will have collapsed to less than 5V. The power dissipated during this phase of charging is approximately 30mW. That is a ten
5V WALL ADAPTER (300mA) USB POWER (200mA) D1 2 MP1 VCC BAT LTC4080X PROG 4 1
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times improvement over the non-current limited supply power dissipation. USB and Wall Adapter Power Although the LTC4080X allows charging from a USB port, a wall adapter can also be used to charge Li-Ion batteries. Figure 3 shows an example of how to combine wall adapter and USB power inputs. A P-channel MOSFET, MP1, is used to prevent back conducting into the USB port when a wall adapter is present and Schottky diode, D1, is used to prevent USB power loss through the 1k pulldown resistor. Typically a wall adapter can supply significantly more current than the current-limited USB port. Therefore, an N-channel MOSFET, MN1, and an extra program resistor can be used to increase the charge current when the wall adapter is present.
ICHG SYSTEM LOAD
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Li-Ion BATTERY
MN1 1.33k 1k
2k
4080X F03
Figure 3. Combining Wall Adapter and USB Power
Power Dissipation The conditions that cause the LTC4080X battery charger to reduce charge current through thermal feedback can be approximated by considering the total power dissipated in the IC. For high charge currents, the LTC4080X power dissipation is approximately: PD = ( VCC - VBAT ) * IBAT + PD _ BUCK Where PD is the total power dissipated within the IC, VCC is the input supply voltage, VBAT is the battery voltage, IBAT is the charge current and PD_BUCK is the power dissipation due to the regulator. PD_BUCK can be calculated as: 1 PD _ BUCK = VOUT * IOUT - 1
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LTC4080X APPLICATIO S I FOR ATIO
Where VOUT is the regulated output of the switching regulator, IOUT is the regulator load and is the regulator efficiency at that particular load. It is not necessary to perform worst-case power dissipation scenarios because the LTC4080X will automatically reduce the charge current to maintain the die temperature at approximately 115C. However, the approximate ambient temperature at which the thermal feedback begins to protect the IC is: TA = 115C - PDJA TA = 115C - (VCC - VBAT) * IBAT * JA if the regulator is off. Example: Consider the extreme case when an LTC4080X is operating from a 6V supply providing 250mA to a 3V Li-Ion battery and the regulator is off. The ambient temperature above which the LTC4080X will begin to reduce the 250mA charge current is approximately: TA = 115C - (6V - 3V) * (250mA) * 43C/W TA = 115C - 0.75W * 43C/W = 115C - 32.25C TA = 82.75C If there is more power dissipation due to the regulator, the thermal regulation will begin at a somewhat lower temperature. In the above circumstances, the LTC4080X can be used above 82.75C, but the charge current will be reduced from 250mA. The approximate current at a given ambient temperature can be calculated: I BAT = 115 C - T A ( VCC - VBAT ) * JA
Using the previous example with an ambient temperature of 85C, the charge current will be reduced to approximately: 115 C - 85 C 30 C I BAT = = = 2 3 2 . 6mA (6V - 3V ) * 43C / W 129 C / A Furthermore, the voltage at the PROG pin will change proportionally with the charge current as discussed in the Programming Charge Current section.
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VCC Bypass Capacitor Many types of capacitors can be used for input bypassing; however, caution must be exercised when using multi-layer ceramic capacitors. Because of the self-resonant and high Q characteristics of some types of ceramic capacitors, high voltage transients can be generated under some start-up conditions, such as connecting the battery charger input to a live power source. Adding a 1 series resistor in series with an X5R ceramic capacitor will minimize start-up voltage transients. For more information, refer to Application Note 88. SWITCHING REGULATOR Setting the Buck Converter Output Voltage The LTC4080X regulator compares the FB pin voltage with an internal 0.8V reference to generate an error signal at the output of the error amplifier. A voltage divider from VOUT to ground (as shown in the Block Diagram) programs the output voltage via FB using the formula: R7 VOUT = 0 . 8 V * 1 + R8 Keeping the current low (<5A) in these resistors maximizes efficiency, but making them too low may allow stray capacitance to cause noise problems and reduce the phase margin of the error amp loop. To improve the frequency response, a phase-lead capacitor (CPL) of approximately 10pF can be used. Great care should be taken to route the FB line away from noise sources, such as the inductor or the SW line. Inductor Selection The value of the inductor primarily determines the current ripple in the inductor. The inductor ripple current IL decreases with higher inductance and increases with higher VIN or VOUT: IL = VOUT f0 * L V * 1 - OUT VIN Accepting larger values of IL allows the use of low inductances, but results in higher output voltage ripple, greater core losses, and lower output current capability. A
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LTC4080X APPLICATIO S I FOR ATIO
reasonable starting point for setting ripple current is IL =0.3 * ILIM, where ILIM is the peak switch current limit. The largest ripple current occurs at the maximum input voltage. To guarantee that the ripple current stays below a specified maximum, the inductor value should be chosen according to the following equation:
L VOUT f0 * IL VOUT * 1- VIN(MAX )
For applications with VOUT = 1.8V, the above equation suggests that an inductor of at least 6.8H should be used for proper operation. Many different sizes and shapes of inductors are available from numerous manufacturers. To maximize efficiency, choose an inductor with a low DC resistance. Keep in mind that most inductors that are very thin or have a very small volume typically have much higher core and DCR losses and will not give the best efficiency. Also choose an inductor with a DC current rating at least 1.5 times larger than the peak inductor current limit to ensure that the inductor does not saturate during normal operation. To minimize radiated noise, use a toroid, or shielded pot core inductors in ferrite or permalloy materials. Table 1 shows a list of several inductor manufacturers.
Table 1. Recommended Surface Mount Inductor Manufacturers
Coilcraft Sumida Murata Toko www.coilcraft.com www.sumida.com www.murata.com www.tokoam.com
Input and Output Capacitor Selection Since the input current waveform to a buck converter is a square wave, it contains very high frequency components. It is strongly recommended that a low equivalent series resistance (ESR) multilayer ceramic capacitor be used to bypass the BAT pin which is the input for the converter. Tantalum and aluminum capacitors are not recommended because of their high ESR. The value of the capacitor on BAT directly controls the amount of input voltage ripple for a given load current. Increasing the size of this capacitor will reduce the input ripple.
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To prevent large VOUT voltage steps during transient load conditions, it is also recommended that a ceramic capacitor be used to bypass VOUT. A typical value for this capacitor is 4.7F. Multilayer Ceramic Chip Capacitors (MLCC) typically have exceptional ESR performance. MLCCs combined with a carefully laid out board with an unbroken ground plane will yield very good performance and low EMI emissions. There are several types of ceramic capacitors with considerably different characteristics. Y5V ceramic capacitors have apparently higher packing density but poor performance over their rated voltage or temperature ranges. Under given voltage and temperature conditions, X5R and X7R ceramic capacitors should be compared directly by case size rather than specified value for a desired minimum capacitance. Some manufacturers provide excellent data on their websites about achievable capacitance. Table 2 shows a list of several ceramic capacitor manufacturers.
Table 2. Recommended Ceramic Capacitor Manufacturers
Taiyo Yuden AVX Murata TDK www.t-yuden.com www.avxcorp.com www.murata.com www.tdk.com
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Board Layout Considerations To be able to deliver maximum charge current under all conditions, it is critical that the exposed metal pad on the backside of the LTC4080X's package has a good thermal contact to the PC board ground. Correctly soldered to a 2500mm2 double-sided 1 oz. copper board, the LTC4080X has a thermal resistance of approximately 43C/W. Failure to make thermal contact between the exposed pad on the backside of the package and the copper board will result in thermal resistances far greater than 43C/W. Furthermore due to its high frequency switching circuitry, it is imperative that the input capacitor, BAT pin capacitor, inductor, and the output capacitor be as close to the LTC4080X as possible and that there is an unbroken ground plane under the LTC4080X and all of its high frequency components.
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LTC4080X PACKAGE DESCRIPTIO U
DD Package 10-Lead Plastic DFN (3mm x 3mm)
(Reference LTC DWG # 05-08-1699)
R = 0.115 TYP 6 0.675 0.05 0.38 0.10 10 3.00 0.10 (4 SIDES) PACKAGE OUTLINE 0.25 0.05 0.50 BSC 2.38 0.05 (2 SIDES) PIN 1 TOP MARK (SEE NOTE 6) 0.200 REF 0.75 0.05 5 1 1.65 0.10 (2 SIDES)
(DD10) DFN 1103
3.50 0.05 1.65 0.05 2.15 0.05 (2 SIDES)
0.25 0.05 0.50 BSC
0.00 - 0.05
2.38 0.10 (2 SIDES) BOTTOM VIEW--EXPOSED PAD
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS NOTE: 1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2). CHECK THE LTC WEBSITE DATA SHEET FOR CURRENT STATUS OF VARIATION ASSIGNMENT 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE
MSE Package 10-Lead Plastic MSOP (Reference LTC DWG # 05-08-1664)
BOTTOM VIEW OF EXPOSED PAD OPTION
2.794 0.102 (.110 .004)
0.889 0.127 (.035 .005)
1
2.06 0.102 (.081 .004) 1.83 0.102 (.072 .004)
3.00 0.102 (.118 .004) (NOTE 3) 10 9 8 7 6
0.497 0.076 (.0196 .003) REF
5.23 (.206) MIN
2.083 0.102 3.20 - 3.45 (.082 .004) (.126 - .136)
4.90 0.152 (.193 .006)
3.00 0.102 (.118 .004) (NOTE 4)
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0.50 0.305 0.038 (.0197) BSC (.0120 .0015) TYP RECOMMENDED SOLDER PAD LAYOUT
DETAIL "A" 0 - 6 TYP 0.18 (.007) DETAIL "A" SEATING PLANE
1.10 (.043) MAX
0.86 (.034) REF
0.254 (.010) GAUGE PLANE
0.53 0.152 (.021 .006) NOTE: 1. DIMENSIONS IN MILLIMETER/(INCH) 2. DRAWING NOT TO SCALE 3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
0.17 - 0.27 (.007 - .011) 0.50 TYP (.0197) BSC
0.127 0.076 (.005 .003)
MSOP (MSE) 0603
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
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Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
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LTC4080X TYPICAL APPLICATIO
Li-Ion Battery Charger with 1.5V Buck Regulator
R3 510 D1 VCC (3.75V to 5.5V) VCC R4, 510 ACPR D2 CIN 4.7F LTC4080X CHRG L1, 1OH* SW FB PROG RPROG 806 *COILCRAFT LPO1704-103M R2 806k
4080X TA02
EFFICIENCY (%)
EN_CHRG EN_BUCK MODE GND
RELATED PARTS
PART NUMBER Battery Chargers LTC3550 Dual Input USB/AC Adapter Li-Ion Battery Charger Synchronous Buck Converter, Efficiency: 93%, Adjustable Output: 600mA, with Adjustable Output 600mA Buck Converter Charge Current: 950mA Programmable, USB Compatible, Automatic Input Power Detection and Selection Dual Input USB/AC Adapter Li-Ion Battery Charger Synchronous Buck Converter, Efficiency: 93%, Output: 1.875V at 600mA, with 600mA Buck Converter Charge Current: 950mA Programmable, USB Compatible, Automatic Input Power Detection and Selection Standalone Linear Li-Ion Battery Charger with Integrated Pass Transistor in ThinSOTTM Standalone Li-Ion Charger with Thermistor Interface Standalone Li-Ion Charger with Thermistor Interface Standalone Linear Li-Ion Battery Charger with Micropower Comparator Li-Ion Charger with Linear Regulator Standalone 500mA Charger with 300mA Synchronous Buck Thermal Regulation Prevents Overheating, C/10 Termination 4.2V, 0.35% Float Voltage, Up to 1A Charge Current, 3mm x 3mm DFN Package 4.4V (Max), 0.4% Float Voltage, Up to 1A Charge Current, 3mm x 3mm DFN Package Up to 1A Charge Current, Charges from USB Port, Thermal Regulation 3mm x 3mm DFN Package Up to 1A Charge Current, 100mA, 125mV LDO, 3mm x 3mm DFN Package For 1-Cell Li-Ion/Polymer Batteries; Trickle Charge; Timer Termination +C/10; Thermal Regulation, Buck Output: 0.8V to VBAT, Buck Input: 2.7V to 5.5V, 3mm x 3mm DFN-10 Package DESCRIPTION COMMENTS
LTC3550-1
LTC4054 LTC4061 LTC4061-4.4 LTC4062 LTC4063 LTC4080
Power Management LTC3405/LTC3405A 300mA (IOUT), 1.5MHz, Synchronous Step-Down 95% Efficiency, VIN: 2.7V to 6V, VOUT = 0.8V, IQ = 20A, ISD < 1A, DC/DC Converter ThinSOT Package LTC3406/LTC3406A 600mA (IOUT), 1.5MHz, Synchronous Step-Down 95% Efficiency, VIN: 2.5V to 5.5V, VOUT = 0.6V, IQ = 20A, ISD < 1A, DC/DC Converter ThinSOT Package LTC3411 LTC3440 LTC4411/LTC4412 LTC4413 1.25A (IOUT), 4MHz, Synchronous Step-Down DC/DC Converter 600mA (IOUT), 2MHz, Synchronous Buck-Boost DC/DC Converter Low Loss PowerPathTM Controller in ThinSOT Dual Ideal Diode in DFN 95% Efficiency, VIN: 2.5V to 5.5V, VOUT = 0.8V, IQ = 60A, ISD < 1A, MS Package 95% Efficiency, VIN: 2.5V to 5.5V, VOUT = 2.5V, IQ = 25A, ISD < 1A, MS Package Automatic Switching Between DC Sources, Load Sharing, Replaces ORing Diodes 2-Channel Ideal Diode ORing, Low Forward On-Resistance, Low Regulated Forward Voltage, 2.5V VIN 5.5V
4080Xf LT 0307 * PRINTED IN USA
ThinSOT and PowerPath are trademarks of Linear Technology Corporation.
20 Linear Technology Corporation
(408) 432-1900 FAX: (408) 434-0507
1630 McCarthy Blvd., Milpitas, CA 95035-7417
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2007
U
Buck Efficiency vs Load Current (VOUT = 1.5V)
100 1000 EFFICIENCY (Burst) EFFICIENCY (PWM)
500mA
80
BAT CBAT 4.7F CPL 10pF
100 POWER LOSS (mW) POWER LOSS 10 (PWM) POWER LOSS (Burst) 1
+
4.2V Li-Ion BATTERY
60
R1 715k
VOUT (1.5V/300mA) COUT 4.7F
40
20
0 0.01
VBAT = 3.8V 0.1 VOUT = 1.5V L = 10H C = 4.7F 0.01 0.1 1 10 100 1000 LOAD CURRENT (mA) 4080X G13

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