PIN DESCRIPTION
PIN #
1
2
3
PIN
NAME
V
IN
GATE
VDR
DESCRIPTION
Input power supply for the controller. Place input decoupling capacitor as close
as possible to this pin.
Connect to the gate terminal of the external P-channel MOSFET.
Power supply for the internal driver. This voltage is internally regulated to
about 5V below V
IN
. Place a 0.1uF decoupling capacitor between VDR and
V
IN
as close as possible to the IC.
Regulator feedback input. Connect to a resistive voltage-divider network to set
the output voltage. This pin can be also used for ON/OFF control. If this pin is
pulled above 1V the P-channel driver is disabled and controller resets internal
soft start circuit.
Ground pin.
This pin is used as a current limit input for the internal current limit comparator.
Connect to the drain pin of the external MOSFET through an optional resistor.
Internal threshold is pre-set to 300mV nominal and can be decreased by
changing the external resistor based on the following formula:
V
TRSHLD
= 300mV – 30uA * R
BLOCK DIAGRAM
4
5
FB
GND
6
LX
5V
VIN
VDR
Oscillator
Vin - 5V LDO
VIN
5V Internal LDO
I = k x VIN
FAULT
VREF
PWM Latch
Reset Dominant
S
GATE
FB
+
+
-
-
R
Error Amplifier
PWM Comparator
VDR
FAULT
FAULT
ENBL
UVLO
FAULT
Register
S
4-Bit counter
-
LX
200ms delay
Overcurrent
Comparator
VIN - 0.3V
+
-
R
R
Set Dominant
POR
1V
Nov07-08
RevG
SP6126: TSOT-6 PFET Buck Controller
3
+
30uA
GND
2008 Exar Corporation
EXAR [ EXAR CORPORATION ]
