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LTC3204-3.3/LTC3204-5/ LTC3204B-3.3/LTC3204B-5 Low Noise Regulated Charge Pump in 2 x 2 DFN U
LTC3204B-5 50 75 100 125 OUTPUT CURRENT (mA) 150
3204 TA01b
FEATURES

DESCRIPTIO

Fixed 3.3V or 5V Outputs VIN Range: 1.8V to 4.5V (LTC3204-3.3/LTC3204B-3.3) 2.7V to 5.5V (LTC3204-5/LTC3204B-5) Output Current: Up to 150mA (LTC3204-5/LTC3204B-5) Up to 50mA (LTC3204-3.3/LTC3204B-3.3) Automatic Burst Mode(R) Operation with IQ = 48A (LTC3204-3.3/LTC3204-5) Constant Frequency Operation at All Loads (LTC3204B-3.3/LTC3204B-5) Low Noise Constant Frequency (1.2MHz) Operation* Built-In Soft-Start Reduces Inrush Current Shutdown Disconnects Load from Input Shutdown Current <1A Short-Circuit/Thermal Protection Available in Low Profile 6-Lead DFN Package 2 AA Cell to 3.3V Li-Ion to 5V USB On-The-Go Devices White LED Drivers Handheld Devices
The LTC(R)3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5 are low noise, constant frequency (1.2MHz) switched capacitor voltage doublers. The LTC3204-3.3/LTC3204B-3.3 can produce a regulated output voltage of 3.3V from a minimum input voltage of 1.8V (2 alkaline cells) whereas the LTC3204-5/LTC3204B-5 can produce 5V from a minimum of 2.7V (Li-Ion battery) input. LTC3204-3.3/LTC3204-5 feature automatic Burst Mode(R) operation at light loads to maintain low supply current whereas LTC3204B-3.3/LTC3204B-5 feature constant frequency operation at any load. Built-in soft-start circuitry prevents excessive inrush current during start-up. Thermal shutdown and current-limit circuitry allow the parts to survive a continuous short-circuit from VOUT to GND. High switching frequency minimizes overall solution footprint by allowing the use of tiny ceramic capacitors. In shutdown, the load is disconnected from the input and the quiescent current is reduced to <1A. The LTC3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5 are available in a low profile (0.75mm) 6-lead 2mm x 2mm DFN package.
, LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Burst Mode is a registered trademark of Linear Technology Corporation. *Protected by U.S. Patents including 6411531.
APPLICATIO S

2.2F 25 2.7V TO 5.5V 2.2F 1, 7 6 2 OUTPUT RIPPLE (mVp-p) VIN 5 C- 4 C+ 3 VOUT 20 15 10 5 0
LTC3204-5/ LTC3204B-5 GND SHDN
OFF ON
U
TYPICAL APPLICATIO
U
Output Ripple vs Load Current
30 OUTPUT CAPACITANCE = 2.2F VIN = 3.6V
5V 2.2F
LTC3204-5
3204 TA01a
0
25
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1
LTC3204-3.3/LTC3204-5/ LTC3204B-3.3/LTC3204B-5
(Note 1)
VIN to GND ................................................... -0.3V to 6V VOUT to GND ............................................. -0.3V to 5.5V SHDN to GND............................................... -0.3V to 6V VOUT Short-Circuit Duration ............................. Indefinite Operating Temperature Range (Note 2) ...-40C to 85C Storage Temperature Range.................. -65C to 125C Maximum Junction Temperature .......................... 125C
TOP VIEW GND 1 VIN 2 VOUT 3 7 6 SHDN 5 C- 4 C+
DC PACKAGE 6-LEAD (2mm x 2mm) PLASTIC DFN TJMAX = 125C, JA = 80C/W EXPOSED PAD IS GND (PIN 7) MUST BE SOLDERED TO PCB
ORDER PART NUMBER LTC3204EDC-3.3 LTC3204EDC-5 LTC3204BEDC-3.3 LTC3204BEDC-5 DC PART MARKING LBJV LBNK LBVF LBVG
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
SYMBOL VIN VOUT PARAMETER Input Voltage Range Output Voltage Range CONDITIONS
The denotes the specifications which apply over the full operating temperature range. Specifications are at TA = 25C, VIN = 2.4V (LTC3204-3.3/LTC3204B-3.3) or 3.6V (LTC3204-5/LTC3204B-5), SHDN = VIN, CFLY = 2.2F, CIN = 2.2F, COUT = 2.2F unless otherwise noted.
MIN

TYP
MAX 4.5 5.5
UNITS V V V V A A mA mA A mA mA mVP-P % MHz V V A A mA ms
IIN
No Load Input Current
ISHDN IBURST VR fOSC VIH VIL IIH IIL ROL ILIM TSS
Shutdown Current Burst Mode Threshold Output Ripple Efficiency Switching Frequency SHDN Input Threshold SHDN Input Threshold SHDN Input Current SHDN Input Current Effective Open-Loop Output Resistance (Note 3) Output Current Limit Soft-Start Time
(LTC3204-3.3/LTC3204B-3.3) (LTC3204-5/LTC3204B-5) 1.8V < VIN < 4.5V, IOUT < 40mA 1.9V < VIN < 4.5V, IOUT < 50mA (LTC3204-3.3/LTC3204B-3.3) 2.7V < VIN < 5.5V, IOUT < 65mA 3.1V < VIN < 5.5V, IOUT < 150mA (LTC3204-5/LTC3204B-5) IOUT = 0 (LTC3204-3.3) IOUT = 0 (LTC3204-5) IOUT = 0 (LTC3204B-3.3) IOUT = 0 (LTC3204B-5) SHDN = 0V, VOUT = 0V (LTC3204-3.3) (LTC3204-5) IOUT = 100mA VIN = 3V, IOUT = 100mA (LTC3204-5/LTC3204B-5)
1.8 2.7 3.168 4.8 3.3 5 48 60 1.25 3.6 15 20 20 82 1.2
3.432 5.2
1

0.6 1.3 -1 -1
1.8 0.4 1 1
SHDN = 0V VIN = 1.8V, VOUT = 3V (LTC3204-3.3/LTC3204B-3.3) VIN = 2.7V, VOUT = 4.5V (LTC3204-5/LTC3204B-5) VOUT = OV From the Rising Edge of SHDN to 90% of VOUT
7 6 300 0.75
Note 1: Absolute Maximum Ratings are those beyond which the life of a device may be impaired. Note 2: The LTC3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5 are guaranteed to meet performance specifications from 0C to 70C.
Specifications over the -40C to 85C operating temperature range are assured by design, characterization and correlation with statistical process controls. Note 3: ROL (2VIN - VOUT)/IOUT
3204fa
2
U
W
U
U
WW
W
ABSOLUTE
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
LTC3204-3.3/LTC3204-5/ LTC3204B-3.3/LTC3204B-5 TYPICAL PERFOR A CE CHARACTERISTICS
(TA = 25C, CFLY = CIN = COUT = 2.2F unless otherwise specified) Oscillator Frequency vs Supply Voltage
1.50 1.25 FREQUENCY (MHz) 1.00 0.75 0.50 0.25 0 FREQUENCY (MHz) 1.4 1.3 1.2 1.1 1.0 0.9 0.8 -50 0.5 1.5 VIN = 2.4V VIN = 1.8V VIN = 4.5V THRESHOLD VOLTAGE (V) 0.8
1.5
2.0
2.5 3.0 3.5 SUPPLY VOLTAGE (V)
SHDN LO-to-HI Threshold vs Temperature
0.9 SHDN THRESHOLD LO-TO-HI (V) SHDN THRESHOLD HI-TO-LO (V) 0.8
0.8 VIN = 3.2V 0.7 VIN = 2.4V
0.7
SHORT-CIRCUIT CURRENT (mA)
0.6
VIN = 1.8V
0.5 -50
0
50 TEMPERATURE (C)
100
UW
4.0
3204 G01 3204 G04
Oscillator Frequency vs Temperature
0.9
SHDN Threshold Voltage vs Supply Voltage
LOW-TO-HIGH THRESHOLD
0.7 HIGH-TO-LOW THRESHOLD 0.6
4.5
-20
10 40 70 TEMPERATURE (C)
100
130
2.0
2.5 3.0 3.5 SUPPLY VOLTAGE (V)
4.0
4.5
3204 G02
3204 G03
SHDN HI-to-LO Threshold vs Temperature
350 VIN = 3.2V VIN = 2.4V 0.6 300 250 200 150 100 50
Short-Circuit Current vs Supply
DEVICE CYCLES IN AND OUT OF THERMAL SHUTDOWN
0.5
VIN = 1.8V
150
0.4 -50
0
50 TEMPERATURE (C)
100
150
3204 G05
0 1.5
2.0
2.5 3.0 3.5 SUPPLY VOLTAGE (V)
4.0
4.5
3204 G06
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LTC3204-3.3/LTC3204-5/ LTC3204B-3.3/LTC3204B-5 TYPICAL PERFOR A CE CHARACTERISTICS
(TA = 25C, CFLY = CIN = COUT = 2.2F unless otherwise specified) Load Regulation
3.35 3.30 OUTPUT VOLTAGE (V) 3.25 VIN = 3.2V 3.20 3.15 3.10 3.05 VIN = 1.8V LOAD CURRENT (mA) 400 350 300 250 200 150 100 50 500
3204 G07
VIN = 2.4V 0 100 200 300 400 LOAD CURRENT (mA)
No-Load Input Current vs Supply Voltage
64 62 NO-LOAD INPUT CURRENT (A) 60 58 56 54 52 50 48 46 44 1.8 2 2.2 2.4 2.6 2.8 SUPPLY VOLTAGE (V) 3 3.2
3204 G10
EXCESS INPUT CURRENT (mA)
LTC3204B-3.3
EFFICIENCY (%)
LTC3204-3.3
VOUT Soft-Start Response
VOUT 2V/DIV
SHDN 2V/DIV VIN = 2.4V ILOAD = 50mA 500s/DIV
3204 3204 G13 G13
4
UW
(LTC3204-3.3/LTC3204B-3.3 ONLY)
Output Load Capability at 4% Below Regulation
VOUT = 3.168V TA = 25C TA = 90C TA = -45C 8 9
Effective Open-Loop Output Resistance vs Temperature
VIN = 1.8V VOUT = 3V
7
6
0 1.5
2.5 3.0 2.0 SUPPLY VOLTAGE (V)
3.5
3204 G08
5 -50
50 0 TEMPERATURE (C)
100
3204 G09
Extra Input Current vs Load Current (IIN-2ILOAD)
2.0 1.8 NO-LOAD INPUT CURRENT (mA) 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 0.01 0.01 0.1 1 10 100 LOAD CURRENT (mA) 1000
3204 G11
Efficiency vs Supply Voltage
100 90 80 70 60 50 40 30 20 10 0 1.8 2.0 2.2 2.4 2.6 2.8 SUPPLY VOLTAGE (V) 3.0 3.2 IOUT = 30mA THEORETICAL MAX
10
VIN = 2.4V LTC3204B-3.3 (NON-BURST MODE OPERATION)
1 LTC3204-3.3 (BURST MODE OPERATION)
IOUT = 1mA
0.1
3204 G12
Output Ripple
Load Transient Response
VOUT 20mV/DIV (AC COUPLED)
VOUT 20mV/DIV (AC COUPLED)
IOUT VIN = 2.4V ILOAD = 50mA 500ns/DIV
3204 3204 G14 G14
50mA 30mA 10s/DIV VIN = 2.4V IOUT = 30mA TO 50mA STEP
3204 3204 G15 G15
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LTC3204-3.3/LTC3204-5/ LTC3204B-3.3/LTC3204B-5 TYPICAL PERFOR A CE CHARACTERISTICS
(TA = 25C, CFLY = CIN = COUT = 2.2F unless otherwise specified) Load Regulation
5.20 5.10
OUTPUT VOLTAGE (V)
OUTPUT LOAD (mA)
5.00 4.90 4.80 4.70 4.60 4.50 0 100 400 300 LOAD CURRENT (mA) 200 500
3204 G16
VIN = 3.6V VIN = 2.7V
No-Load Input Current vs Supply Voltage
70 68
NO-LOAD INPUT CURRENT (A)
LTC3204-5
EXCESS INPUT CURRENT (mA)
66 64 62 60 58 56 54 52 50 2.7 3 3.6 3.9 3.3 SUPPLY VOLTAGE (V) 4.2 LTC3204B-5
EFFICIENCY (%)
VOUT Soft-Start
VOUT 2V/DIV
SHDN 5V/DIV VIN = 3.6V IOUT = 100mA 500s/DIV
3204 G22
UW
VIN = 4.2V
3204 G19
(LTC3204-5/LTC3204B-5 ONLY)
Output Load Capability at 4% Below Regulation
500 450 400 350 300 250 200 150 100 50 0 2.7 3.0 3.3 3.6 3.9 SUPPLY VOLTAGE (V) 4.2
3204 G17
Effective Open-Loop Output Resistance vs Temperature
8 VIN = 2.7V VOUT = 4.5V
VOUT = 4.8V TA = 90C TA = 25C
7
TA = -45C
6
5
4 -50
0
50
100
3204 G18
TEMPERATURE (C)
Extra Input Current vs Load Current (IIN-2ILOAD)
4.0 3.6
NO-LOAD INPUT CURRENT (mA)
Efficiency vs Supply Voltage
100 90 80 70 60 50 40 30 20 10 IOUT = 100mA IOUT = 10mA IOUT = 1mA THEORETICAL MAX
10
VIN = 3.6V LTC3204B-5 (N0N-BURST MODE OPERATION) LTC3204-5 (BURST-MODE OPERATION)
3.2 2.8 2.4 2.0 1.6 1.2 0.8 0.4 0 4.5
1
0.1
0.01 0.01
0.1
1 10 100 LOAD CURRENT (mA)
1000
3204 G20
0 2.7
3.0
3.3 3.6 3.9 SUPPLY VOLTAGE (V)
4.2
4.5
3204 G21
Output Ripple
Load Transient Response
VOUT 20mV/DIV (AC COUPLED)
VOUT 50mV/DIV (AC COUPLED) 100mA 60mA VIN = 3.6V IOUT = 100mA 500ns/DIV
3204 G23
IOUT
10s/DIV VIN = 3.6V IOUT = 60mA TO 100mA STEP
3204 G24
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LTC3204-3.3/LTC3204-5/ LTC3204B-3.3/LTC3204B-5 PI FU CTIO S
GND (Pin 1, 7): Ground. These pins should be tied to a ground plane for best performance. The exposed pad must be soldered to PCB ground to provide electrical contact and optimum thermal performance. VIN (Pin 2): Input Supply Voltage. VIN should be bypassed with a 1F to 4.7F low ESR ceramic capacitor. VOUT (Pin 3): Regulated Output Voltage. VOUT should be bypassed with a low ESR ceramic capacitor providing at least 2F of capacitance as close to the pin as possible for best performance.
VIN
2 C-
6
-
+
W
BLOCK DIAGRA
U
U
U
C+ (Pin 4): Flying Capacitor Positive Terminal. C- (Pin 5): Flying Capacitor Negative Terminal. SHDN (Pin 6): Active Low Shutdown Input. A low on SHDN disables the LTC3204-3.3/LTC3204-5/LTC3204B-3.3/ LTC3204B-5. This pin must not be allowed to float.
SOFT-START AND SWITCH CONTROL VOUT 3 1.2MHz OSCILLATOR
6
SHDN
CHARGE PUMP 4 C+
5
3204 BD
GND
1, 7
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LTC3204-3.3/LTC3204-5/ LTC3204B-3.3/LTC3204B-5
The LTC3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5 use a switched capacitor charge pump to boost VIN to a regulated output voltage. Regulation is achieved by sensing the output voltage through an internal resistor divider and modulating the charge pump output current based on the error signal. A 2-phase nonoverlapping clock activates the charge pump switches. The flying capacitor is charged from VIN on the first phase of the clock. On the second phase of the clock it is stacked in series with VIN and connected to VOUT. This sequence of charging and discharging the flying capacitor continues at a free running frequency of 1.2MHz (typ). Shutdown Mode In shutdown mode, all circuitry is turned off and the LTC3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5 draws only leakage current from the VIN supply. Furthermore, VOUT is disconnected from VIN. The SHDN pin is a CMOS input with a threshold voltage of approximately 0.7V. The LTC3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5 are in shutdown when a logic low is applied to the SHDN pin. Since the SHDN pin is a very high impedance CMOS input, it should never be allowed to float. To ensure that its state is defined, it must always be driven with a valid logic level. Since the output voltages of these devices can go above the input voltage, special circuitry is required to control the internal logic. Detection logic will draw an input current of 5A when the devices are in shutdown. However, this current will be eliminated if the output voltage (VOUT) is less than approximately 0.8V. Burst Mode Operation The LTC3204-3.3/LTC3204-5 provide automatic Burst Mode operation to reduce supply current at light loads. Burst Mode operation is initiated if the output load current falls below an internally programmed threshold. Once
U
OPERATIO
(Refer to the Block Diagram)
Burst Mode operation is initiated, the part shuts down the internal oscillator to reduce the switching losses and goes into a low current state. This state is referred to as the sleep state in which the IC consumes only about 40A from the input. When the output voltage droops enough to overcome the burst comparator hysteresis, the part wakes up and commences normal fixed frequency operation. The output capacitor recharges and causes the part to reenter the sleep state if the output load still remains less than the Burst Mode threshold. This Burst Mode threshold varies with VIN, VOUT and the choice of output storage capacitor. Soft-Start The LTC3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5 have built-in soft-start circuitry to prevent excessive current flow during start-up. The soft-start is achieved by charging an internal capacitor with a very weak current source. The voltage on this capacitor, in turn, slowly ramps the amount of current available to the output storage capacitor from zero to a value of 300mA over a period of approximately 0.75ms. The soft-start circuit is reset in the event of a commanded shutdown or thermal shutdown. Short-Circuit/Thermal Protection The LTC3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5 have built-in short-circuit current limit as well as over-temperature protection. During a short-circuit condition, they will automatically limit their output current to approximately 300mA. At higher temperatures, or if the input voltage is high enough to cause excessive self-heating of the part, the thermal shutdown circuitry will shutdown the charge pump once the junction temperature exceeds approximately 160C. It will enable the charge pump once the junction temperature drops back to approximately 150C. The LTC3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5 will cycle in and out of thermal shutdown indefinitely without latchup or damage until the short-circuit condition on VOUT is removed.
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LTC3204-3.3/LTC3204-5/ LTC3204B-3.3/LTC3204B-5
Power Efficiency The power efficiency () of the LTC3204-3.3/LTC3204-5/ LTC3204B-3.3/LTC3204B-5 is similar to that of a linear regulator with an effective input voltage of twice the actual input voltage. This occurs because the input current for a voltage doubling charge pump is approximately twice the output current. In an ideal regulating voltage doubler the power efficiency would be given by: = POUT VOUT * IOUT VOUT = = PIN VIN * 2IOUT 2VIN
EFFECTIVE OPEN-LOOP OUTPUT RESISTANCE ()
At moderate to high output power, the switching losses and the quiescent current of the LTC3204-3.3/LTC3204-5/ LTC3204B-3.3/LTC3204B-5 are negligible and the expression above is valid. For example, with VIN = 3V, IOUT = 100mA and VOUT regulating to 5V, the measured efficiency is 81.8% which is in close agreement with the theoretical 83.3% calculation. Maximum Available Output Current For the LTC3204-3.3/LTC3204-5/LTC3204B-3.3/ LTC3204B-5,the maximum available output current and voltage can be calculated from the effective open-loop output resistance, ROL, and the effective input voltage, 2VIN(MIN).
ROL
+
IOUT VOUT
+ -
2VIN
-
3204 F01
Figure 1. Equivalent Open-Loop Circuit
From Fig. 1, the available current is given by: IOUT = 2VIN - VOUT ROL
Effective Open Loop Output Resistance (ROL) The effective open loop output resistance (ROL) of a charge pump is a very important parameter which determines the strength of the charge pump. The value of this parameter depends on many factors such as the oscillator frequency
8
U
(fOSC), value of the flying capacitor (CFLY), the nonoverlap time, the internal switch resistances (RS), and the ESR of the external capacitors. A first order approximation for ROL is given below: ROL 2 RS +
S=1 TO 4
APPLICATIO S I FOR ATIO W UU
1 f OSC * C FLY
Typical ROL values as a function of temperature are shown in Figure 2.
8 VIN = 2.7V VOUT = 4.5V
7
6
5
4 -50
0
50
100
3204 F02
TEMPERATURE (C)
Figure 2. Typical ROL vs Temperature
VIN, VOUT Capacitor Selection The style and value of capacitors used with the LTC3204-3.3/ LTC3204-5/LTC3204B-3.3/LTC3204B-5 determine several important parameters such as regulator control loop stability, output ripple, charge pump strength and minimum start-up time. To reduce noise and ripple, it is recommended that low ESR (<0.1) ceramic capacitors be used for both CIN and COUT. These capacitors should be 1F or greater. Tantalum and aluminum capacitors are not recommended because of their high ESR. The value of COUT directly controls the amount of output ripple for a given load current. Increasing the size of COUT will reduce the output ripple at the expense of higher minimum turn-on time. The peak-to-peak output ripple is approximately given by the expression: VRIPPLE(P -P) IOUT 2f OSC * C OUT
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LTC3204-3.3/LTC3204-5/ LTC3204B-3.3/LTC3204B-5
where f OSC is the oscillator frequency (typically 1.2MHz) and COUT is the value of output charge storage capacitor. Also, the value and style of the output capacitor can significantly affect the stability of the LTC3204-3.3/LTC3204-5/ LTC3204B-3.3/LTC3204B-5. As shown in the Block Diagram, the LTC3204-3.3/LTC3204-5/LTC3204B3.3/LTC3204B-5 use a linear control loop to adjust the strength of the charge pump to match the current required at the output. The error signal of this loop is stored directly on the output storage capacitor. This output capacitor also serves to form the dominant pole of the control loop. To prevent ringing or instability on the LTC3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5, it is important to maintain at least 1F of capacitance over all conditions. Excessive ESR on the output capacitor can degrade the loop stability of the LTC3204-3.3/LTC3204-5/LTC3204B-3.3/ LTC3204B-5. The closed loop output resistance of the LTC3204-5 is designed to be 0.5. For a 100mA load current change, the output voltage will change by about 50mV. If the output capacitor has 0.5 or more of ESR, the closed loop frequency response will cease to roll off in a simple one-pole fashion and poor load transient response or instability could result. Ceramic capacitors typically have exceptional ESR performance and combined with a good board layout should yield very good stability and load transient performance. As the value of COUT controls the amount of output ripple, the value of CIN controls the amount of ripple present at the input pin (VIN). The input current to the LTC3204-3.3/ LTC3204-5/LTC3204B-3.3/LTC3204B-5 will be relatively constant during the input charging phase or the output charging phase but will drop to zero during the nonoverlap times. Since the nonoverlap time is small (~25ns), these missing notches will result in only a small perturbation on the input power supply line. Note that a higher ESR capacitor such as tantalum will have higher input noise due to the voltage drop in the ESR. Therefore, ceramic capacitors are again recommended for their exceptional ESR performance. Further input noise reduction can be achieved by powering the LTC3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5
U
through a very small series inductor as shown in Figure 3. A 10nH inductor will reject the fast current notches, thereby presenting a nearly constant current load to the input power supply. For economy, the 10nH inductor can be fabricated on the PC board with about 1cm (0.4") of PC board trace.
1cm OF WIRE 10nH VIN 2 2.2F 1 VIN LTC3204-3.3/ LTC3204-5 GND
32005 F03
APPLICATIO S I FOR ATIO W UU
0.22F
Figure 3. 10nH Inductor Used for Additional Input Noise Reduction
Flying Capacitor Selection Warning: A polarized capacitor such as tantalum or aluminum should never be used for the flying capacitor since its voltage can reverse upon start-up of the LTC3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5. Low ESR ceramic capacitors should always be used for the flying capacitor. The flying capacitor controls the strength of the charge pump. In order to achieve the rated output current, it is necessary to have at least 1F of capacitance for the flying capacitor. For very light load applications, the flying capacitor may be reduced to save space or cost. From the first order approximation of ROL in the section "Effective Open-Loop Output Resistance," the theoretical minimum output resistance of a voltage doubling charge pump can be expressed by the following equation: R0L(MIN) = 2VIN - VOUT 1 IOUT f OSC * C FLY
where fOSC is the switching frequency (1.2MHz) and CFLY is the value of the flying capacitor. The charge pump will typically be weaker than the theoretical limit due to additional switch resistance. However, for very light load applications, the above expression can be used as a guideline in determining a starting capacitor value.
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LTC3204-3.3/LTC3204-5/ LTC3204B-3.3/LTC3204B-5
Ceramic Capacitors Ceramic capacitors of different materials lose their capacitance with higher temperature and voltage at different rates. For example, a capacitor made of X5R or X7R material will retain most of its capacitance from -40C to 85C whereas a Z5U or Y5V style capacitor will lose considerable capacitance over that range. Z5U and Y5V capacitors may also have a poor voltage coefficient causing them to lose 60% or more of their capacitance when the rated voltage is applied. Therefore when comparing different capacitors, it is often more appropriate to compare the amount of achievable capacitance for a given case size rather than discussing the specified capacitance value. For example, over rated voltage and temperature conditions, a 1F 10V Y5V ceramic capacitor in a 0603 case may not provide any more capacitance than a 0.22F 10V X7R capacitor available in the same 0603 case. In fact, for most LTC3204-3.3/ LTC3204-5/LTC3204B-3.3/LTC3204B-5 applications, these capacitors can be considered roughly equivalent. The capacitor manufacturer's data sheet should be consulted to ensure the desired capacitance at all temperatures and voltages. Below is a list of ceramic capacitor manufacturers and how to contact them:
AVX Kemet Murata Taiyo Yuden Vishay TDK www.avxcorp.com www.kemet.com www.murata.com www.t-yuden.com www.vishay.com www.component.tdk.com
CIN 0603 VIN VOUT COUT 0603 C+
Layout Considerations Due to the high switching frequency and high transient currents produced by LTC3204-3.3/LTC3204-5/LTC3204B3.3/LTC3204B-5, careful board layout is necessary for optimum performance. A true ground plane and short connections to all the external capacitors will improve performance and ensure proper regulation under all conditions. Figure 4 shows an example layout for the LTC3204-3.3/ LTC3204-5/LTC3204B-3.3/LTC3204B-5.
10
U
GND C- CFLY 0603 SHDN
3204 F04
APPLICATIO S I FOR ATIO W UU
Figure 4. Recommended Layout
Thermal Management For higher input voltages and maximum output current, there can be substantial power dissipation in the LTC3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5. If the junction temperature increases above approximately 160C, the thermal shutdown circuitry will automatically deactivate the output. To reduce the maximum junction temperature, a good thermal connection to the PC board is recommended. Connecting the GND pin (Pin 1) and the exposed pad of the DFN package (Pin 7) to a ground plane under the device on two layers of the PC board can reduce the thermal resistance of the package and PC board considerably. Derating Power at High Temperatures To prevent an overtemperature condition in high power applications, Figure 5 should be used to determine the maximum combination of ambient temperature and power dissipation. The power dissipated in the LTC3204-3.3/LTC3204-5/ LTC3204B-3.3/LTC3204B-5 should always fall under the line shown for a given ambient temperature. The power dissipation in the LTC3204-3.3/ LTC3204-5/LTC3204B-3.3/ LTC3204B-5 is given by the expression: PD = (2VIN - VOUT )* IOUT This derating curve assumes a maximum thermal resistance, JA, of 80C/W for the 2mm x 2mm DFN package.
3204fa
LTC3204-3.3/LTC3204-5/ LTC3204B-3.3/LTC3204B-5
This can be achieved from a printed circuit board layout with a solid ground plane and a good connection to the ground pins of LTC3204-3.3/LTC3204-5/LTC3204B-3.3/ LTC3204B-5 and the exposed pad of the DFN package.
3.0 2.5 POWER DISSIPATION (W) 2.0 1.5 1.0 0.5 0 -50 -25
Figure 5. Maximum Power Dissipation vs Ambient Temperature
0.675 0.05 2.50 0.05 1.15 0.05 0.61 0.05 (2 SIDES) 2.00 0.10 (4 SIDES)
0.25 0.05 0.50 BSC 1.42 0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
NOTE: 1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WCCD-2) 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
3204fa
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.
U
PACKAGE DESCRIPTIO
DC Package 6-Lead Plastic DFN (2mm x 2mm)
(Reference LTC DWG # 05-08-1703)
PIN 1 BAR PACKAGE TOP MARK OUTLINE (SEE NOTE 6)
U
Operation out of this curve will cause the junction temperature to exceed 160C which may trigger the thermal shutdown.
25 50 75 100 125 150 0 AMBIENT TEMPERATURE (C)
3204 G05
APPLICATIO S I FOR ATIO W UU
R = 0.115 TYP 0.56 0.05 (2 SIDES)
0.38 0.05 4 6
PIN 1 CHAMFER OF EXPOSED PAD 3 1
(DC6) DFN 1103
0.200 REF
0.75 0.05
0.25 0.05 0.50 BSC
1.37 0.05 (2 SIDES) 0.00 - 0.05 BOTTOM VIEW--EXPOSED PAD
11
LTC3204-3.3/LTC3204-5/ LTC3204B-3.3/LTC3204B-5 TYPICAL APPLICATIO S U
Regulated 3.3V Output
2.2F 5 C- 4 C+ 3 VOUT
VIN 1.8V TO 4.5V 2.2F
2
VIN
1, 7 6
LTC3204-3.3/ LTC3204B-3.3 GND SHDN
VOUT 3.3V 2.2F
OFF ON
3204 TA02
Lithium-Ion Battery to 5V White or Blue LED Driver
2.2F 5 2 3V TO 4.4V Li-Ion BATTERY ON OFF 2.2F 6 C- VIN 4 C+ 3 VOUT 2.2F 1, 7 DRIVE UP TO 5 LEDS 100 100 100 100 100
LTC3204-5/ LTC3204B-5 SHDN GND VSHDN
(APPLY PWM WAVEFORM FOR ADJUSTABLE BRIGHTNESS CONTROL)
t
3200-5 TA03
USB Port to Regulated 5V Power Supply
2.2F 5 4 C+ VOUT
C- 2 VIN
3
LTC3204-5 2.2F 6 SHDN GND 1, 7 2.2F
VOUT 5V 4%
32005 TA05
RELATED PARTS
PART NUMBER LTC1751-3.3/ LTC1751-5 LTC1983-3/ LTC1983-5 LTC3200-5 LTC3202 DESCRIPTION 100mA, 800kHz Regulated Doubler 100mA, 900kHz Regulated Inverter 100mA, 2MHz Low Noise, Doubler/ White LED Driver 125mA, 1.5MHz Low Noise, Fractional White LED Driver COMMENTS VIN: 2V to 5V, VOUT(MAX) = 3.3V/5V, IQ = 20A, ISD <2A, MS8 Package VIN: 3.3V to 5.5V, VOUT(MAX) = -3V/-5V, IQ = 25A, ISD <1A, ThinSOT Package VIN: 2.7V to 4.5V, VOUT(MAX) = 5V, IQ = 3.5mA, ISD <1A, ThinSOT Package VIN: 2.7V to 4.5V, VOUT(MAX) = 5.5V, IQ = 2.5mA, ISD <1A, DFN, MS Packages
3204fa LT/LT 0605 * PRINTED IN USA
12 Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
FAX: (408) 434-0507 www.linear.com
LINEAR TECHNOLOGY CORPORATION 2004

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