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MicroPower, 620kHz PWM, Step-up DC/DC Converter
POWER MANAGEMENT Description
The SC1417B is a fixed frequency, current mode step-up dc-dc converter. It operates over a wide input supply range of 1.5V to 12V, making it suitable for battery input and TFT-LCD applications. The 620kHz constant frequency oscillator minimizes the size of external components and allows simple filtering for noise sensitive environments. The integrated power NPN supports peak currents of up to 0.9A enabling the device to support 150mA at 15V from a 5V supply. The maximum switch duty cycle of 85% (typical) allows output to input voltage ratios as high as 6.5 in step-up configurations, thus allowing 2V to 12V boost operation. The SC1417B features a low battery detector and a 200mV reference circuit which remains active during shut down. The part consumes less than 50A in shutdown. The low battery detect output goes low when the input battery voltage has dropped below a user programmable level. Pulse-by-pulse current limit and thermal shutdown protect the converter during load faults. The SC1417B is available in a MSOP-8 surface mount package.
SC1417B
Features
Operates from 1.5V to 12V supply voltage High efficiency >85% 150mA @ 15V from 5V input Internal switch peak current of 0.9A Programmable output voltage Powers up into full load Pulse-by-pulse current limit/thermal shutdown 620kHz fixed frequency current mode converter Low current shutdown mode extends battery life 18V output capability Low battery detector MSOP-8 package. Available in Lead-free package, fully WEEE and RoHS compliant Pin-for-pin compatible with LT1317B
Applications
TFT-LCD Bias supplies Constant current LED bias supplies Pagers GPS receivers Battery backup SEPIC converters
Typical Application Circuit
L1 10uH R2 1M C1 47uF R3 1M U1 6 7 3 1 IN LBI EN COMP LX FB LBO GND 5 2 8 4 C2 47uF R4 604k D1
SMB5819 R1 1.0M
3.3V@250mA
VOUT = 1.22 * (1 +
R1 ) R4
SC1417B
(Alkaline)
2 Cells
R6 130k
LBO OUT R5 33k C3 3.3nF
Revision: August 1, 2006
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SC1417B
POWER MANAGEMENT Absolute Maximum Ratings
Exceeding the specifications below may result in permanent damage to the device, or device malfunction. Operation outside of the parameters specified in the Electrical Characteristics section is not implied.
Parameter Input Supply Voltage LX Input LBI Input EN Input FB Input LBO Output COMP Output Operating Ambient Temperature Range Operating Junction Temperature Range Thermal Impedance, Junction to Ambient Thermal Impedance, Junction to Case Storage Temperature Range Lead Temperature (Soldering) 10 Sec.
Symbol VIN V LX V LB I V EN V FB V LB O VCOMP TA TJ J A J C TSTG TLEAD
Maximum 15 -0.4 to 20 -0.3 to 6 -0.3 to 6 -0.3 to 6 -0.3 to 15 -0.3 to 6 -40 to 85 -40 to 125 163 63 -65 to 150 300
Units V V V V V V V C C C/W C/W C C
Electrical Characteristics
Unless otherwise specified: TA = 25C. Values in bold apply over full operating ambient temperature range. VIN = 2V, VEN = 2V, All voltages are with respect to ground, -ve indicates current is flowing out of the pin.
Parameter Input Voltage
Symbol VIN
Conditions VFB = 1.22V
Min 1.5 2.0
Typ
Max 12 12
Units V
Feedback Voltage Supply Current in Shutdown
V FB IQ(OFF)
VCOMP = 600mV, LX floating VEN = 0V, VLBI = 300mV
1.16
1.22 40
1.28 55 65
V A
Supply Current in PWM Mode Feedback Input Current Error Amplifier Transconductance
IQ IFB Gm
IOUT = 0A, VCOMP = 100mV VFB = 1.22V dlCOMP = 5A 70
4.3 15 140
5.8 60 240
mA nA S
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SC1417B
POWER MANAGEMENT Electrical Characteristics
Unless otherwise specified: TA = 25C. Values in bold apply over full operating ambient temperature range. VIN = 2V, VEN = 2V, All voltages are with respect to ground, -ve indicates current is flowing out of the pin.
Parameter Error Amplifier Voltage Gain(1) Maximum Output Current, L = 22uH
(1)
Symbol AV(E.A.) IOUT
Conditions
Min
Typ 700
Max
Units V/V mA mA mA
VOUT = 5.0V, VIN = 2.0V VOUT = 10V, VIN = 5.0V VOUT = 15V, VIN = 5.0V
200 250 150 150 250 500
Power Switch Voltage Drop
(1)
(VLX-GND)
ILX = 500mA
mV
Power Switch Current Limit
ILIM
0C TA 85C -40C TA 85C
0.70 0.60
0.95
1.20
A
Switch Leakage Internal Oscillator Frequency Maximum Duty Cycle Low Battery Input Voltage Threshold
ILX fOSC %DC V LB I
V LX = 5 V LX , E N open 520 80 190 180
0.01 620 85 200
3 720
A kHz %
210 210
mV
LBI Input Current Low Battery Output Low Low Battery Detector Gain (1) Enable Inputs Enable Input Voltage
ILBI VLBO(L) AV
VLBI = 100mV ILBO = 5A 1M load
-5 75 2000
-40 250
nA mV V/V
VIH VIL
1.4
0.6 0.60 0.25 300
V V nA A
Enable Pin Current
IIH IIL VSHDN = 0V -2.3
-6.0
Notes: (1) Guaranteed by design. (2) This device is ESD sensitive. Use of standard ESD handling precautions is required.
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SC1417B
POWER MANAGEMENT Pin Configuration Ordering Information
Part Number SC1417BIMSTR(1) P ackag e MSOP-8 MSOP-8 Evaluation Board
TOP VIEW
COMP FB EN GND 1 2 3 4 8 7 6 5 LBO LBI IN LX
SC1417BIMSTRT(1)(2) S C 1417B E V B
Note: (1) Only available in tape and reel packaging. A reel contains 2500 devices. (2) Available in lead-free packaging only. This product is fully WEEE and RoHS compliant.
(MSOP-8)
Pin Descriptions
Pin # 1 Pin Name COMP Pin Function C ompensati on pi n for error ampli fi er. C onnect a seri es RC network from thi s pi n to ground for frequency compensation. Typical values are 33k/3.3nF. Placing a 100pF - 10nF capacitor from this pin to ground reduces the output and input capacitor values required for stability at the expense of slower transient response. Feedback pin. Connect to the output through a voltage divider to set output voltage.
VOUT = 1.22 * (1 + R1 ) R4
2
FB
3 4 5 6 7
EN GND LX IN LB I
Enable pin. Pull this pin low for shutdown mode. The device quiescent current reduces to 40A (typ.). This pin can be left floating or pulled up to a voltage less then 6V to enable the device. Ground. Switch pin (the inductor and diode junction). Keep traces on this pin short and wide to minimize EMI. Supply pin. Bypass this pin to GND with a capacitor as close to pins 4 and 6 as possible. Low battery detector input. Connect to IN through a voltage divider to set low battery indicator threshold.
VTH(LO ) = 0.2 * (1 + R2 ) R6
8
LB O
Low battery detector open collector output. This pin pulls low when VLBI is below 200mV (typ.). Pullup using a 1M resistor.
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SC1417B
POWER MANAGEMENT Block Diagram
COMP IN
1.22V REFERENCE ERROR AMP FB ENABLE EN
COMP SLOPE COMP
LX Q3
PWM LOGIC
DRV
620kHz OSCILLATOR LBO LBM 200mV CURRENT AMP
.05 Ohm
LBI
GND
Marking Information
Marking for MSOP-8 package
yyww = Date Code (Example: 0012) xxxxxxxx = Semtech Lot No. (Example: E90101-1)
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SC1417B
POWER MANAGEMENT Typical Characteristics
Feedback Voltage vs. Temperature
1.250 1.245 1.240 1.235 IQ(OFF) (A) VFB (V) 1.230 1.225 1.220 1.215 1.210 1.205 1.200 -50 -25 0 25 TA (C) 50 75 100 0 -50 -25 0 25 TA (C) 50 75 100 VIN = VEN = 2V VCOMP = 600mV LX floating 60 50 40 30 20 10 VIN = 2V VEN = 0V VLBI = 300mV
Supply Current in Shutdown vs. Temperature
Supply Current in PWM Mode vs. Temperature
5.3 5.1 4.9 4.7 IFB (nA) IQ (mA) 4.5 4.3 4.1 3.9 3.7 3.5 3.3 -50 -25 0 25 TA (C) 50 75 100 VIN = VEN = 2V IOUT = 0A VCOMP = 100mV 50 45 40 35 30 25 20 15 10 5 0 -50 -25
Feedback Input Current vs. Temperature
VIN = VEN = 2V VFB = 1.22V
0
25 TA (C)
50
75
100
Power Switch Voltage Drop vs. Temperature
400 350 300 (VLX - GND) (mV) 250 ILIM (A) 200 150 100 50 0 -50 -25 0 25 TA (C) 50 75 100 VIN = VEN = 2V ILX = 500mA 1.20 1.15 1.10 1.05 1.00 0.95 0.90 0.85 0.80 0.75 0.70 -50
Power Switch Current Limit vs. Temperature
VIN = VEN = 2V
-25
0
25 TA (C)
50
75
100
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SC1417B
POWER MANAGEMENT Typical Characteristics (Cont.)
Internal Oscillator Frequency vs. Temperature
670 660 650 640 fOSC (kHz) VLBI (mV) 630 620 610 600 590 580 570 -50 -25 0 25 TA (C) 50 75 100 VIN = 3.6V VOUT = 5V IOUT = 20mA 205 204 203 202 201 200 199 198 197 196 195 -50 -25 0 25 TA (C) 50 75 100 VIN = VEN = 2V
Low Battery Input Voltage Threshold vs. Temperature
Low Battery Output Low vs. Temperature
150 125 100 VLBO(L) (mV) 75 50 25 0 -50 -25 0 25 TA (C) 50 75 100 VEN (V) VIN = VEN = 2V VLBI = 100mV ILBO = 10A 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 -50 VIN = 2V
Enable Voltage Threshold vs. Temperature
-25
0
25 TA (C)
50
75
100
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SC1417B
POWER MANAGEMENT Typical Characteristices (Cont.)
90 80
2-Cell to 5V Converter Efficiency
Efficiency (%)
70 60 50 40
Vin 3.0V Vin 2.2V Vin 1.65V 1 10 Load current (mA) 100 1000
Scope plot of Boost Converter waveforms in Constant Brightness LED driver Vin = 3V, Vout = 11.9V, Iout = 40mA, L = 15uH Cin = 10uF, 6.3V tant. Cout = 1uF, ceramic, (see above schematic for other components used) Ch1: Switching Node, Ch2: Vout ripple, Ch4: Current in inductor, (100mA/div) Inductor current ripple = 170mA pk-pk
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SC1417B
POWER MANAGEMENT Typical Application Circuits(1)
L1 VIN 15uH R2 1M R3 1M 6 7 3 1 C1 22uF,6.3V R6 130k C6 10nF R5 33k C3 2.2nF GND GND R4 D1 SMB5819 VOUT LED,3.5V LX FB LBO GND 5 2 8 4 LED,3.5V
25 mA out (12V compliant)
U1 IN LBI EN COMP
SC1417B LED,3.5V LBO OUT C2 4.7uF,16V
IOUT
1.22 V = R4
Inductor: Falco P/N SDIP0302-156 (305) 622-9076 or Coilcraft P/N DT1608C-153 (847) 639-6400
Figure 1 - Constant Brightness LED driver with 12V compliance from 2-cells (constant current output)
VIN = 2V to 5V
L1 15uH
D1 SMB5819
VOUT = 12V, 75mA
R2 1M C1 10uF,6.3V
U1 6 7 3 1 IN LBI EN COMP LX FB LBO GND 5 2 8 4
R1 1.00M
1uF,16V C2 R4 115k R3 1M
SC1417B R6 130k R5 33k C3 2.2nF
C6 10nF
LBO OUT
ENABLE GND
GND
Figure 2 - Minimum Capacitance Boost Converter Note: (1) Value of C1 depends on proximity of input source voltage and source impedance (use C1 > 47F if the input supply is greater than two inches from the SC1417B).
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SC1417B
POWER MANAGEMENT Outline Drawing - MSOP-8
DIMENSIONS INCHES MILLIMETERS DIM MIN NOM MAX MIN NOM MAX
D
A A1 A2 b c D E1 E e L L1 N 01 aaa bbb ccc .043 .000 .006 .030 .037 .015 .009 .009 .003 .114 .118 .122 .114 .118 .122 .193 BSC .026 BSC .016 .024 .032 (.037) 8 8 0 .004 .005 .010 1.10 0.15 0.00 0.95 0.75 0.38 0.22 0.08 0.23 2.90 3.00 3.10 2.90 3.00 3.10 4.90 BSC 0.65 BSC 0.40 0.60 0.80 (.95) 8 0 8 0.10 0.13 0.25
e/2 A N 2X E/2 PIN 1 INDICATOR ccc C 2X N/2 TIPS 12 e B E1 E
aaa C SEATING PLANE
D A2 A GAGE PLANE 0.25
H c
C
A1 bxN bbb C A-B D
L (L1) DETAIL
01
A
SIDE VIEW
NOTES: 1.
SEE DETAIL
A
CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES).
2. DATUMS -A- AND -B- TO BE DETERMINED AT DATUM PLANE -H3. DIMENSIONS "E1" AND "D" DO NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. 4. REFERENCE JEDEC STD MO-187, VARIATION AA.
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SC1417B
POWER MANAGEMENT Land Pattern - MSOP-8
X
DIM
(C) G Z C G P X Y Z
DIMENSIONS INCHES MILLIMETERS
(.161) .098 .026 .016 .063 .224 (4.10) 2.50 0.65 0.40 1.60 5.70
Y P
NOTES: 1. THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY. CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES ARE MET.
Contact Information
Semtech Corporation Power Management Products Division 200 Flynn Road, Camarillo, CA 93012 Phone: (805) 498-2111 FAX (805)498-3804 Visit us at: www.semtech.com
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