LTC3807_15 Datasheet, PDF (10/32 Pages) Linear Technology – Low IQ, Synchronous Step-Down Controller with 24V Output Voltage Capability

LTC3807
PIN FUNCTIONS
EXTV_CC (Pin 15/Pin 17): External Power Input to an
Internal LDO Connected to INTV_CC. This LDO supplies
INTV_CC power, bypassing the internal LDO powered from
V_IN whenever EXTV_CC is higher than 4.7V. See EXTV_CC
Connection in the Applications Information section. Do
not float or exceed 14V on this pin. Connect to ground
(SGND or PGND) if not used.
PGND (Pin 16/Pin 18): Driver Power Ground. Connects to
the source of bottom (synchronous) N-channel MOSFET
and the (–) terminal of C_IN.
V_IN (Pin 17/Pin 19): Main Supply Pin. A bypass capacitor
should be tied between this pin and the SGND pins.
I_LIM (Pin 18/Pin 20): Current Comparator Sense Voltage
Range Inputs. Tying this pin to SGND, FLOAT or INTV_CC
sets the maximum current sense threshold to one of three
different levels for the comparator.
TRACK/SS (Pin 19/Pin 1): External Tracking and Soft-Start
Input. The LTC3807 regulates the V_FB voltage to the smaller
of 0.8V or the voltage on the TRACK/SS pin. An internal
10μA pull-up current source is connected to this pin. A
capacitor to ground at this pin sets the ramp time to final
regulated output voltage. Alternatively, a resistor divider
on another voltage supply connected to this pin allows the
LTC3807 output to track another supply during start-up.
FREQ (Pin 20/Pin 2): The frequency control pin for the
internal VCO. Connecting the pin to GND forces the VCO
to a fixed low frequency of 350kHz. Connecting the pin
to INTV_CC forces the VCO to a fixed high frequency of
535kHz. Other frequencies between 50kHz and 900kHz
can be programmed by using a resistor between FREQ
and GND. An internal 20µA pull-up current develops the
voltage to be used by the VCO to control the frequency.
3807f
10
For more information www.linear.com/LTC3807