Datasheet LT1944-1 (Analog Devices)

LT1944-1 Dual Micropower Step-Up DC/DC Converter
U FEATURES DESCRIPTIO
■
Low Quiescent Current:
The LT®1944-1 is a dual micropower step-up DC/DC
20
µ
A in Active Mode
converter in a 10-pin MSOP package. One converter is
<1
µ
A in Shutdown Mode
designed with a 100mA current limit and a 400ns off-time; ■
Operates with V
the other with a 175mA current limit and a 1.5
IN as Low as 1.2V
µs off-time. ■ Low V The 1.5 CESAT Switches: 85mV at 70mA µs off-time converter is ideal for generating an ■ Uses Small Surface Mount Components output voltage that is close to the input voltage (i.e. a Li- ■ High Output Voltage: Up to 34V Ion to 5V converter, or a two-cell to 3.3V converter). With ■ Tiny 10-Pin MSOP Package an input voltage range of 1.2V to 15V, the LT1944-1 is ideal for a wide variety of applications. Both converters feature
U
a quiescent current of only 20µA at no load, which further
APPLICATIO S
reduces to 0.5µA in shutdown. A current limited, fixed off- ■ time control scheme conserves operating current, result- Small TFT LCD Panels ■ ing in high efficiency over a broad range of load current. Handheld Computers ■ Tiny, low profile inductors and capacitors can be used to Battery Backup ■ minimize footprint and cost in space-conscious portable Digital Cameras applications. , LTC and LT are registered trademarks of Linear Technology Corporation.
U TYPICAL APPLICATIO Triple Output Power Supply (5V, 15V, –10V) for LCD Displays
L1
5V Output Efficiency
22 V µH D1 IN 5V 2.7V 90 40mA TO 4.2V 8 6 85 4.7pF 1M VIN SW2 V 4 5 80 IN = 4.2V SHDN2 FB2 C1 75 LT1944-1 C2 VIN = 2.7V 4.7µF 4.7µF 2 1 70 SHDN1 FB1 324k GND PGND PGND SW1 65 EFFICIENCY (%) 3 7 9 10 60 178k 55 C3 50 4.7pF 2M 0.1 1 10 100 1µF L2 LOAD CURRENT (mA) 22µH D2 15V 1944-1 TA01a 2.5mA D3 C1, C2: TAIYO YUDEN JMK212BJ475 C4 C3, C4: TAIYO YUDEN EMK212BJ105 5V 1µF C5: TAIYO YUDEN EMK107BJ104 C5 D1, D2, D3, D4: CENTRAL SEMI CMDSH3 0.1µF D4 –10V L1, L2: MURATA LQH3C220 1944-1 TA01 1mA 1