Datasheet

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LT1317/LT1317B

Micropower, 600kHz PWM

DC/DC Converters

DESCRIPTION

FEATURES

The LT

1317/LT1317B are micropower, fixed frequency

step-up DC/DC converters that operate over a wide input

voltage range of 1.5V to 12V. The LT1317 features auto-

matic shifting to power saving Burst Mode

operation at

light loads. High efficiency is maintained over a broad

300µA to 200mA load range. Peak switch current during

Burst Mode operation is kept below 250mA for most

operating conditions which results in low output ripple

voltage, even at high input voltages. The LT1317B does

not shift into Burst Mode operation at light loads, eliminat-

ing low frequency output ripple at the expense of light load

efficiency.

The LT1317/LT1317B contain an internal low-battery de-

tector with a 200mV reference that stays alive when the

device goes into shutdown.

No-load quiescent current of the LT1317 is 100µA and

shuts down to 30µA. The internal NPN power switch

handles a 500mA current with a voltage drop of just

300mV.

The LT1317/LT1317B are available in MS8 and SO-8

packages.

■

100µA Quiescent Current

■

Operates with V

as Low as 1.5V

■

600kHz Fixed Frequency Operation

■

Starts into Full Load

■

Low-Battery Detector Active in Shutdown

■

Automatic Burst Mode Operation at

Light Load (LT1317)

■

Continuous Switching at Light Loads (LT1317B)

■

Low V

CESAT

Switch: 300mV at 500mA

■

Pin for Pin Compatible with the LT1307/LT1307B

■

Cellular Telephones

■

Cordless Telephones

■

Pagers

■

GPS Receivers

■

Battery Backup

■

Portable Electronic Equipment

■

Glucose Meters

■

Diagnostic Medical Instrumentation

APPLICATIONS

Burst Mode is a trademark of Linear Technology Corporation.

, LTC and LT are registered trademarks of Linear Technology Corporation.

TYPICAL APPLICATION

Figure 1. 2-Cell to 3.3V Boost Converter

LT1317

L1

10µH

LBO

LBI

SHDNSHUTDOWN



33k

R2*

604k

3.3V

200mA

R1

1M



3.3nF

1317 F01

C1

47µF

C2

47µF

2

CELLS

D1: MBR0520

L1: SUMIDA CD43-100

* FOR 5V OUTPUT, R2 = 332k, 1%

GND

2-Cell to 3.3V Converter Efficiency

LOAD CURRENT (mA)

EFFICIENCY (%)

0.3 10 100 1000

1317 TA01

1.65V

2.2V

Summary of content (16 pages)

PAGE 1
LT1317/LT1317B Micropower, 600kHz PWM DC/DC Converters U DESCRIPTION FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ 100µA Quiescent Current Operates with VIN as Low as 1.
PAGE 2
LT1317/LT1317B W W W AXI U U ABSOLUTE RATI GS (Note 1) VIN, LBO Voltage ..................................................... 12V SW Voltage ............................................... – 0.4V to 30V FB Voltage .................................................... VIN + 0.3V VC Voltage ................................................................ 2V LBI Voltage ............................................ 0V ≤ VLBI ≤ 1V SHDN Voltage ............................................................
PAGE 3
LT1317/LT1317B ELECTRICAL CHARACTERISTICS Commercial Grade SYMBOL VIN = 2V, VSHDN = 2V, TA = 25°C unless otherwise noted. PARAMETER CONDITIONS Shutdown Pin Current VSHDN = VIN VSHDN = 0V MIN ● ● LBI Threshold Voltage ● 190 180 TYP MAX UNITS 0.015 – 2.3 0.06 –6 µA µA 200 200 210 220 mV mV LBO Output Low ISINK = 10µA ● 0.15 0.25 V LBO Leakage Current VLBI = 250mV, VLBO = 5V ● 0.02 0.
PAGE 4
LT1317/LT1317B U W TYPICAL PERFOR A CE CHARACTERISTICS Oscillator Frequency 1000 800 VIN = 2V L = 10µH 25°C 85°C 600 550 0 2 4 6 8 INPUT VOLTAGE 10 900 SWITCH CURRENT (mA) –40°C 650 SWITCH CURRENT (mA) OSCILLATOR FREQUENCY (kHz) 700 500 600 400 200 0 20 40 60 DUTY CYCLE (%) 800 600 MINIMUM (25°C) 400 200 20 40 60 DUTY CYCLE (%) 80 5 4 3 2 1 Feedback Voltage 0 25 50 TEMPERATURE (°C) 75 0 25 50 TEMPERATURE (°C) –40°C 300 200 100 0 75 100 1317 TPC07 0.2 0.4 0.6 0.
PAGE 5
LT1317/LT1317B U W TYPICAL PERFOR A CE CHARACTERISTICS Quiescent Current, SHDN = 0V SHDN Pin Current FB Pin Bias Current 26 40 2 36 24 23 22 21 32 SHDN PIN CURRENT (µA) FB PIN BIAS CURRENT (nA) QUIESCENT CURRENT (µA) 25 28 24 20 16 12 1 0 –1 –2 8 4 20 –50 –25 0 25 50 TEMPERATURE (°C) 75 0 –50 100 –3 –25 0 25 50 TEMPERATURE (°C) 1317 TPC10 0 100 80 80 80 EFFICIENCY (%) 90 EFFICIENCY (%) 90 70 60 VIN = 1.65V 50 VIN = 3V 1 10 100 LOAD CURRENT (mA) 60 VIN = 1.
PAGE 6
LT1317/LT1317B U W TYPICAL PERFOR A CE CHARACTERISTICS Load Regulation (LT1317) Load Regulation (LT1317) VOUT 50mV/DIV DC COUPLED OFFSET ADDED Load Regulation (LT1317) VOUT 50mV/DIV DC COUPLED OFFSET ADDED VOUT 50mV/DIV DC COUPLED OFFSET ADDED VIN = 1.
PAGE 7
LT1317/LT1317B W BLOCK DIAGRAM LBI 1.24V REFERENCE + gm FB 2 + 7 VC LBO 8 1 – ERROR AMPLIFIER + – 200mV A4 ENABLE SHDN VOUT BIAS R1 (EXTERNAL) – SHUTDOWN 3 A1 COMPARATOR SW FB 5 – R2 (EXTERNAL) RAMP GENERATOR + Σ + + FF Q3 Q R A2 COMPARATOR DRIVER S + A=2 600kHz OSCILLATOR 0.
PAGE 8
LT1317/LT1317B U W U U APPLICATIONS INFORMATION The LT1317B differs from the LT1317 in that the bias point on A1 is set lower than on the LT1317 so that minimum switch current can drop below 50mA. Because A1’s bias point is set lower, there is no Burst Mode operation at light loads and the device continues switching at constant frequency. This results in the absence of low frequency output voltage ripple at the expense of light load efficiency.
PAGE 9
LT1317/LT1317B U U W U APPLICATIONS INFORMATION Table 1. Inductors Suitable for Use with the LT1317 PART VALUE MAX DCR MFR HEIGHT (mm) LQH3C100 10µH 0.57 Murata-Erie 2.0 DO1608-103 10µH 0.16 Coilcraft 3.0 CD43-100 10µH 0.18 Sumida 3.2 CD54-100 10µH 0.10 Sumida 4.5 Best Efficiency CTX32CT-100 10µH 0.50 Coiltronics 2.
PAGE 10
LT1317/LT1317B U W U U APPLICATIONS INFORMATION FREQUENCY COMPENSATION 10µH The LT1317 has an external compensation pin (VC) which allows the frequency response to be optimized for the circuit configuration. In most cases, the values used in Figure 1 will work. Some circuits may need additional compensation and a simple trial and error method for determining the necessary component values is given. Figure 6 shows the test setup.
PAGE 11
LT1317/LT1317B U U W U APPLICATIONS INFORMATION LOW-BATTERY DETECTOR The LT1317’s low-battery detector is a simple PNP input gain stage with an open collector NPN output. The negative input of the gain stage is tied internally to a 200mV ±5% reference. The positive input is the LBI pin. Arrangement as a low-battery detector is straightforward. Figure 11 details hookup. R1 and R2 need only be low enough in value so that the bias current of the LBI pin doesn’t cause large errors.
PAGE 12
LT1317/LT1317B U TYPICAL APPLICATIO S 5V to 12V Boost Converter L1 22µH 5V to 12V Boost Converter Efficiency 90 MBR0520 VIN + 47µF VOUT 12V 150mA SW FB LT1317 SHUTDOWN SHDN VC 85 EFFICIENCY (%) VIN 5V 1.07M 1% LB0 GND + C2 47µF 124k 1% 56k 80 75 3300pF 70 L1: SUMIDA CD54-220 1317 TA04 10 LOAD CURRENT (mA) 1 100 1317 TA04a Single Li-Ion to 5V DC/DC Converter L1 10µH Single Li-Ion to 5V DC/DC Converter Efficiency 90 MBR0520 47µF SINGLE Li-ION CELL (2.7V TO 4.
PAGE 13
LT1317/LT1317B U TYPICAL APPLICATIO S 2-Cell to 5V DC/DC Converter with Undervoltage Lockout L1 10µH D1 5V 130mA 301k + 100k VIN 22µF 10V LT1317 SW FB VC SHDN 2 ALKALINE CELLS LBO LBI 1M 340k 1M 1% GND 33k 332k 1% + 100µF 10V 3.3nF 470pF D1: MOTOROLA MBR0520LT1 L1: SUMIDA CD43-101 1317 TA07 STARTS AT VIN = 1.9V STOPS AT VIN = 1.6V Universal Wall Cube to 4.1V L1A 20µH VIN 1.5V TO 10V 100k + VIN 15µF 20V LT1317 SHDN VC CERAMIC 10µF, 16V D1 VOUT 4.
PAGE 14
LT1317/LT1317B U TYPICAL APPLICATIO S Single Li-Ion Cell to 4V/70mA, – 4V/10mA D2 4.5V TO 2.5V 1µF CERAMIC VIN SW LT1317 Li-Ion CELL SHUTDOWN SHDN VC + 1µF CERAMIC L1 22µH – 4V 10mA C3 15µF C1 1µF L2 22µH D1 1.00M 4V 70mA FB GND + 100pF 33k 442k C2 33µF 3.3nF C1: MURATA GRM235Y5V107Z01 C2: AVX TAJB336M010 C3: AVX TAJA156M010 D1: MBR0520 D2: BAT54S (DUAL DIODE) L1, L2: MURATA LQH3C220K04 1317 TA02 Low Noise 33V Varactor Bias Supply D3 680Ω 150pF D2 L1 22µH C3 0.
PAGE 15
LT1317/LT1317B U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. MS8 Package 8-Lead Plastic MSOP (LTC DWG # 05-08-1660) 0.118 ± 0.004* (3.00 ± 0.102) 8 7 6 5 0.118 ± 0.004** (3.00 ± 0.102) 0.192 ± 0.004 (4.88 ± 0.10) 1 2 3 4 0.040 ± 0.006 (1.02 ± 0.15) 0.007 (0.18) 0.034 ± 0.004 (0.86 ± 0.102) 0° – 6° TYP SEATING PLANE 0.012 (0.30) 0.0256 REF (0.65) TYP 0.021 ± 0.006 (0.53 ± 0.015) 0.006 ± 0.004 (0.15 ± 0.
PAGE 16
LT1317/LT1317B U TYPICAL APPLICATION Digital Camera Power Supply 10k 24V D3 T1 7 + LC 8 18V 3mA C5 10µF 35V D2 5 + LB 6 LPRI:15µH + C1 22µF 10V 4 AA CELLS (3.2V TO 6.5V) SHUTDOWN 2 D1 3 + LA 1 4 C3 1µF, 16V VIN 5V 20mA C4 22µF 10V C2 100µF 6V 3.3V 150mA SW LT1317 SHDN 1M FB GND VC 10k 604k 3300pF 1317 TA10 C1, C4: AVX TPSC226M016 C2: AVX TPSC106M006 C3: CERAMIC (i.e.