Datasheet LT1944-1 (Analog Devices) - 3

LT1944-1
W U TYPICAL PERFOR A CE CHARACTERISTICS Switch Saturation Voltage Feedback Pin Voltage and (VCESAT) Bias Current Quiescent Current
0.15 1.25 50 25 VFB = 1.23V NOT SWITCHING 0.13 1.24 40 23 BIAS CURRENT (nA) µA) ISWITCH = 100mA VOLTAGE 0.10 1.23 30 21 ISWITCH = 70mA 0.08 VIN = 12V 1.22 CURRENT 20 19 0.05 SWITCH VOLTAGE (V) VIN = 1.2V FEEDBACK VOLTAGE (V) QUIESCENT CURRENT ( 1.21 10 17 0.03 0 1.20 0 15 –50 –25 0 25 50 75 100 –50 –25 0 25 50 75 100 –50 –25 0 25 50 75 100 TEMPERATURE (°C) TEMPERATURE (°C) TEMPERATURE (°C) 1944-1 G01 1944-1 G02 1944-1 G03
Switch Off Time Switch Current Limit Shutdown Pin Current
2000 200 25 1800 VIN = 12V 175 1600 SWITCHER 2 SWITCHER 2 µA) 20 VIN = 1.2V 1400 150 1200 15 1000 125 25°C V 800 IN = 12V 10 100°C 100 600 SWITCH OFF TIME (ns) PEAK CURRENT (mA) V SWITCHER 1 IN = 1.2V SWITCHER 1 5 400 SHUTDOWN PIN CURRENT ( 75 200 0 0 50 –50 –25 100 –50 –25 0 25 50 75 100 0 5 10 15 0 25 50 75 TEMPERATURE (°C) TEMPERATURE (°C) SHUTDOWN PIN VOLTAGE (V) 1944-1 G03 1944-1 G04 1944-1 G05
U U U PI FU CTIO S FB1 (Pin 1):
Feedback Pin for Switcher 1. Set the output
SW2 (Pin 6):
Switch Pin for Switcher 2. This is the voltage by selecting values for R1 and R2. collector of the internal NPN power switch. Minimize the metal trace area connected to the pin to minimize EMI.
SHDN1 (Pin 2):
Shutdown Pin for Switcher 1. Tie this pin to 0.9V or higher to enable device. Tie below 0.25V to turn
PGND (Pins 7, 9):
Power Ground. Tie these pins directly it off. to the local ground plane. Both pins must be tied.
GND (Pin 3):
Ground. Tie this pin directly to the local
VIN (Pin 8):
Input Supply Pin. Bypass this pin with a ground plane. capacitor as close to the device as possible.
SHDN2 (Pin 4):
Shutdown Pin for Switcher 2. Tie this pin
SW1 (Pin 10):
Switch Pin for Switcher 1. This is the to 0.9V or higher to enable device. Tie below 0.25V to turn collector of the internal NPN power switch. Minimize the it off. metal trace area connected to the pin to minimize EMI.
FB2 (Pin 5):
Feedback Pin for Switcher 2. Set the output voltage by selecting values for R1B and R2B. 3