Datasheet

ManualsBrandsLINEAR TECHNOLOGY ManualsPMICsPMIC - DC/DC voltage regulator Boost, SEPIC MSOP 8

LT1949

600kHz, 1A Switch

PWM DC/DC Converter

3.3V

LT1949

10µH

140k

68k

330pF

OUT

10V

175mA

1949 F01

10µF

CERAMIC

22µF

GND

SHDNSHUTDOWN

C1: AVX TAJA226M006R

C2: TAIYO YUDEN LMK325BJ106MN

D1: MBRM120LT3

L1: SUMIDA CDRH62B-100

The LT

1949 is a fixed frequency step-up DC/DC con-

verter with a 1A, 0.5Ω internal switch. Capable of gener-

ating 10V at 175mA from a 3.3V input, the LT1949 is ideal

for generating bias voltages for large screen LCD panels.

Constant frequency 600kHz operation results in a low

noise output that is easy to filter and the 30V switch rating

allows output voltage up to 28V using a single inductor. An

external compensation pin gives the user flexibility in

optimizing loop compensation, allowing small low ESR

ceramic capacitors to be used at the output. The 8-lead

MSOP and SO packages ensure a low profile overall

solution.

The LT1949 includes a low-battery detector that stays

alive when the device goes into shutdown. Quiescent

current in shutdown is 25µA, while operating current is

4.5mA.

■

1A, 0.5Ω, 30V Internal Switch

■

Operates with V

as Low as 1.5V

■

600kHz Fixed Frequency Operation

■

Low-Battery Detector Stays Active in Shutdown

■

Low V

CESAT

Switch: 410mV at 800mA

■

Pin-for-Pin Compatible with the LT1317B

■

Small 8-Lead MSOP and SO Packages

■

LCD Bias Supplies

■

GPS Receivers

■

Battery Backup

■

Portable Electronic Equipment

■

Diagnostic Medical Instrumentation

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

Figure 1. 3.3V to 10V/175mA DC/DC Converter Figure 2. 3.3V to 10V Converter Efficiency

LOAD CURRENT (mA)

5 10050 300

1949 F02

EFFICIENCY (%)

OUT

= 10V

3.6V

4.2V

DESCRIPTIO

FEATURES

APPLICATIO S

TYPICAL APPLICATIO

Summary of content (8 pages)

PAGE 1
LT1949 600kHz, 1A Switch PWM DC/DC Converter U FEATURES ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO The LT ®1949 is a fixed frequency step-up DC/DC converter with a 1A, 0.5Ω internal switch. Capable of generating 10V at 175mA from a 3.3V input, the LT1949 is ideal for generating bias voltages for large screen LCD panels. Constant frequency 600kHz operation results in a low noise output that is easy to filter and the 30V switch rating allows output voltage up to 28V using a single inductor.
PAGE 2
LT1949 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
LT1949 ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. VIN = 2V, VSHDN = 2V unless otherwise noted. SYMBOL PARAMETER CONDITIONS Switch VCESAT ISW = 800mA ISW = 500mA ● 1.8V ≤ VIN ≤ 12V ● Reference Line Regulation MIN MAX UNITS 400 mV mV 0.
PAGE 4
LT1949 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) 75 100 0 –50 –3 –25 0 25 50 TEMPERATURE (°C) 1317 TPC10 75 100 0 2 4 3 SHDN PIN VOLTAGE (V) 5 6 1317 TPC12 1317 TPC11 Load Regulation Load Regulation Transient Response VOUT 100mV/DIV AC COUPLED V
PAGE 5
LT1949 W BLOCK DIAGRA LBI 1.24V REFERENCE + FB 2 1 ERROR AMPLIFIER + – + 7 VC gm LBO 8 – 200mV A4 ENABLE SHDN VOUT BIAS R1 (EXTERNAL) – SHUTDOWN SW FB R2 (EXTERNAL) 3 A1 COMPARATOR 5 – RAMP GENERATOR + Σ + + FF Q3 Q R A2 COMPARATOR DRIVER S + A=2 600kHz OSCILLATOR 0.06Ω – 4 GND 1949 BD Figure 3. LT1949 Block Diagram U OPERATIO The LT1949 is a current mode, fixed frequency step-up DC/DC converter with an internal 1A NPN power transistor.
PAGE 6
LT1949 U OPERATIO LBI LBO GROUND PLANE C1 1 + VIN 8 R1 2 R2 SHUTDOWN LT1949 7 3 6 4 5 L1 MULTIPLE VIAs C2 GND VOUT 1949 F04 Figure 4. Recommended Component Placement for Boost Converter. Note Direct High Current Paths Using Wide PC Traces. Minimize Trace Area at Pin 1 (VC) and Pin 2 (FB). Use Multiple Vias to Tie Pin 4 Copper to Ground Plane.
PAGE 7
LT1949 U TYPICAL APPLICATIO 4 Cell to 5V SEPIC Converter C2 4.7µF 16V L1 10µH VIN 4V TO 9V SW VIN 1M D1 L2 10µH VOUT 5V 250mA 1M 1% LT1949 C1 4.7µF 16V GND VC 1M C3 10µF 6.3V FB SHDN 332k 1% 33k 3.3nF C1, C2: TAIYO YUDEN EMK316BJ475ML C3: TAIYO YUDEN JMK316BJ106ML D1: MOTOROLA MBRM120LT3 L1, L2: SUMIDA CR32-100KC 1949 TA02 U PACKAGE DESCRIPTIO Dimensions in inches (millimeters) unless otherwise noted. MS8 Package 8-Lead Plastic MSOP (LTC DWG # 05-08-1660) 0.040 ± 0.006 (1.02 ± 0.
PAGE 8
LT1949 U TYPICAL APPLICATIO Low Profile Triple Output LCD Bias Generator D1 D2 C7 0.1µF L1 10µH VIN 3.3V SHUTDOWN + 23V 5mA C9 0.1µF 8V 200mA R2 40.2k 1% SHDN LBI C1 22µF C8 0.1µF D4 D7 SW VIN D3 LT1949 C2 10µF FB LB0 VC GND R3 7.5k 1% R1 47k C3 680pF C6 4.7µF C1: AVX TAJB226M010 C2: TAIYO YUDEN TMK432BJ106MN X7R 1210 C4, C5, C6: TAIYO YUDEN LMK316BJ475ML X5R1206 C7, C8, C9: 0.1µF CERAMIC, 50V D1 TO D6: FMMD7000, DUAL DIODE D7: MBRM120LT3 L1: SUMIDA CDRH62B-100 C4 4.7µF D5 C5 4.