SP6125 Datasheet, PDF (3/12 Pages) Sipex Corporation – High-Voltage, Step Down Controller in TSOT6

PIN #
1
2
3
4
5
6
PIN
NAME
VIN
GATE
VDR
FB
GND
LX
PIN DESCRIPTION
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 VIN. Place a 0.1uF decoupling capacitor between VDR and
Vin 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
VIN
5V
Oscillator
Vin - 5V LDO
VDR
FAULT
FB
FAULT
+
-
1V
VIN
I = k x VIN
5V Internal LDO
VREF
+
-
Error Amplifier
PWM Latch
Reset Dominant
S
+
R
-
PWM Comparator
FAULT
GATE
VDR
UVLO
200ms delay
FAULT
Register
S
R
R
Set Dominant
4-Bit counter
POR
ENBL
Overcurrent
Comparator
VIN - 0.3V
LX
30uA
GND
Jan28-08 RevG
SP6125: TSOT-6 PFET Buck Controller
3
 2007 Exar Corporation