Datasheet LTC3870 (Analog Devices) - 7

LTC3870
pin FuncTions FAULT0/FAULT1 (Pin 26/Pin 25):
Fault Input Pins. Con- pin sets the default switching frequency when there is no nect these pins to the master chip GPIO pins to respond external clock on the SYNC pin. Set the frequency close to fault signals from the master controller. If this pin is to the external clock to help the internal PLL sync to the low, both TG and BG pins are pulled down at the corre- SYNC pin clock quickly and smoothly. See the application sponding channel. There is a 500k pull down resistor on section for the detailed information. FAULT0/FAULT1 internally. These pins have to be driven
SGND (Exposed Pad Pin 29):
Signal Ground. All small- high externally for normal operation. signal and compensation components should connect to
FREQ (Pin 27):
Frequency Set Pin. There is a precision this ground, which in turn connects to PGND at one point. 10µA current flowing out of this pin. A resistor to ground The exposed pad must be soldered to the PCB, providing sets a voltage which in turn programs the frequency. This a local ground for the control components of the IC, and be tied to PGND under the IC. 3870fb For more information www.linear.com/LTC3870 7