Datasheet LT3587 (Analog Devices) - 7

LT3587
PIN FUNCTIONS VOUT1 (Pin 14):
Boost1 Output Pin. This pin is the drain
VFB3 (Pin 20):
Boost3 Output Voltage Feedback Pin. Con- of an output disconnect PMOS transistor. nect a resistor RVFB3 from this pin to VOUT3 (or CAP3) such that:
FB1 (Pin 15):
Boost1 Output Voltage Feedback Pin. Con- nect a resistor RFB1 from this pin to VOUT1 (or CAP1) RVFB3 = ((VVOUT3/0.8V) – 1) • 56.3k such that: There is an internal 56.3k resistor from the VFB3 pin to RFB1 = ((VVOUT1/1.22V) – 1) • 88.5k ground. In the current regulator confi guration, RVFB3 can be optionally used to limit the maximum output voltage There is an internal 88.5k resistor from the FB1 pin to to V ground. CLAMP, such that: R
EN/SS1 (Pin 16):
Boost1/Inverter Shutdown and Soft-Start VFB3 = ((VCLAMP/0.8V) – 1) • 56.3k Pin. Boost1 and Inverter are enabled when the voltage Note: When no voltage clamp is desired in the current on this pin is greater than 2.5V. They are disabled when regulator confi guration, tie VFB3 to GND. the voltage is below 0.2V. An internal 1μA current source
Exposed Pad (Pin 21):
Ground Pin. Connect to PCB ground in conjunction with an external capacitor can be used to plane. Ground plane connection through multiple vias under ramp this pin and provide soft-start. the package is recommended for optimum electrical and
VIN (Pin 17):
Input Supply Pin. Must be locally bypassed thermal performance. with an X5R or X7R type ceramic capacitor.
EN/SS3 (Pin 18):
Boost3 Shutdown and Soft-Start Pin. Boost3 is enabled when the voltage on this pin is greater than 2V. It is disabled when the voltage is below 0.2V. An internal 1μA current source in conjunction with an exter- nal capacitor can be used to ramp this pin and provide soft-start.
IFB3 (Pin 19):
Boost3 Output Current Programming Pin. Connect a resistor RIFB3 from this pin to ground such that: RIFB3 = 200 • (0.8V/IVOUT3) If Boost3 output is confi gured as a voltage regulator, RIFB3 can be optionally used to limit the maximum output current to ILIMIT: RIFB3 = 200 • (0.8V/ILIMIT) Note: Tie IFB3 to GND when no current limit is desired. 3587fc 7