LTC3870-1 pin FuncTions to the PCB ground for electrical connection and rated resistor on FAULT0/FAULT1 internally. These pins have to thermal performance. be driven high externally for normal operation. VIN (Pin 17): Main Input Supply. Bypass this pin to GND FREQ (Pin 22): Frequency Set Pin. There is a precision with a capacitor (0.1µF to 1µF). 10µA current flowing out of this pin. A resistor to ground FAULT0 /FAULT1 (Pin 21/Pin 20): Fault Input Pins. Connect sets a voltage which in turn programs the frequency. This these pins to the master chip GPIO pins to respond to pin sets the default switching frequency when there is no fault signals from the master controller. If this pin is low, external clock on the SYNC pin. Setting the frequency close the PWM pin is in three-state. There is a 500kΩ pull-down to the external clock helps the internal PLL sync to the SYNC pin clock quickly and smoothly. See the Application Section for the detailed information. block DiagraM (CH0 Shown) 10 11 15 SYNC PHASMD EXTVCC 10µA SYNC 4.8V DET PHASE – + PROGRAM VIN FREQ V 27 17 PFD IN + CIN VCO OSC S 5.0V 5.0V LDO LDO R Q EN EN ICMP 3K IREV INTV + CC 14 – – + ON VCC0 REV 18 UVLO L SWITCH PWM0 19 DrMOS VOUT0 I I FAULT LOGIC LIM LIM RANGE SELECT C 9 C HI: 1:1 R INTV FCNT C LO: 1:1.5 CC UVLO + RUN COUT0 I + SENSE0 SLOPE 1 COMPENSATION I – SENSE0 2 INTV 1 CC 71.1k + – + – + – 1.7V REF 500k 500k ITH0 MODE0 RUN0 FAULT0 GND 23 24 3 21 16 38701 BD 38701f For more information www.linear.com/LTC3870-1 7 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Order Information Electrical Characteristics Pin Configuration Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Typical Applications Package Description Typical Application Related Parts