Datasheet LTC1876 (Analog Devices) - 9

LTC1876
U U U PIN FUNCTIONS
provides a common control point to shut down both control-
TG1, TG2 (Pins 35, 24):
High Current Gate Drives for Top lers. See the Operation section for details. N-Channel MOSFETs. These are the outputs of floating drivers with a voltage swing equal to INTV
FCB (Pin 7):
Forced Continuous Control Input. This input acts CC – 0.5V superim- posed on the switch node voltage SW. on both controllers and is normally used to regulate a secondary winding. Pulling this pin below 0.8V will force
SW1, SW2 (Pins 34, 25):
Switch Node Connections to continuous synchronous operation on both controllers. Do Inductors. Voltage swing at these pins is from a Schottky not leave this pin floating. diode (external) voltage drop below ground to VIN.
ITH1, ITH2 (Pins 8, 11):
Error Amplifier Output and Switching
BOOST1, BOOST2 (Pins 33, 26):
Bootstrapped Supplies to Regulator Compensation Point. Each associated channel’s the Top Side Floating Drivers. Capacitors are connected current comparator trip point increases with this control between the boost and switch pins and Schottky diodes are voltage. tied between the boost and INTVCC pins. Voltage swing at the boost pins is from INTV
SGND (Pin 9):
Small signal ground common to both control- CC to (VIN + INTVCC). lers, must be routed separately from high current grounds to
BG1, BG2 (Pins 31, 27):
High Current Gate Drives for Bottom the common (–) terminals of the COUT capacitors. (synchronous) N-Channel MOSFETs. Voltage swing at these pins is from ground to INTV
3.3V
CC.
OUT (Pin 10):
Output of a linear regulator capable of supplying up to 10mA DC with peak currents as high as
PGND (Pin 28):
Driver Power Ground. Connects to sources 50mA. of bottom (synchronous) N-channel MOSFETs, anode of the Schottky rectifier and the (–) terminal(s) of C
AUXSGND (Pin 15):
Small Signal Ground of the Auxiliary IN. Boost Regulator.
INTVCC (Pin 29):
Output of the Internal 5V Linear Low Dropout Regulator and the EXTV
AUXV
CC Switch. The driver and
FB (Pin 16):
Auxiliary Boost Regulator Feedback Volt- control circuits are powered from this voltage source. Must age. This pin receives the feedback voltage from an external be decoupled to power ground with a minimum of 4.7µF resistive divider across the auxiliary output. tantalum or other, low ESR capacitor. The INTVCC regulator
AUXSW (Pins 17, 18):
Switch Node Connections to Inductor standby operation is determined by the STBYMD pin. for the Auxiliary Regulator. Voltage swing at these pins are
EXTV
from ground to (V
CC (Pin 30):
External Power Input to an Internal Switch OUT + voltage across Shottky diode). Connected to INTV Minimize trace area at these pins to keep EMI down. CC. This switch closes and supplies VCC power, bypassing the internal low dropout regulator, when-
AUXPGND (Pins 19, 20):
The Auxiliary Power Ground Pins. ever EXTVCC is higher than 4.7V. See EXTVCC connection in Its gate drive currents are returned to these pin. Applications section.
Do not exceed 7V on this pin
.
AUXVIN (Pin 21):
Auxiliary Boost Regulator Controller Sup-
VIN (Pin 32):
Main Supply Pin. A bypass capacitor should be ply Pin. Must be closely decoupled to AUXPGND. tied between this pin and the signal ground pin.
AUXSD (Pin 22):
Shutdown Pin for the Auxiliary Regulator.
PGOOD (Pin 36):
Open-Drain Logic Output. PGOOD is pulled Connect to 2.4V or more to enable the auxiliary regulator or to ground when the voltage on either VOSENSE pin is not within ground to shut the auxiliary regulator off. 7.5% of its setpoint. 1876fa 9