SP7656 EXAR [Exar Corporation], SP7656 Datasheet - Page 3

• Manufacturer Part Number: SP7656
• Description: 3A, 29V Non-Synchronous Buck Converter
• Manufacturer: EXAR [Exar Corporation]

FB
1V
PIN DESCRIPTION
PIN #
11/07/08 SP7656 PowerBlox
4,5
7,9
FAULT
1
2
3
6
8
+
-
5V
FAULT
PIN NAME
PVIN
SVIN
GND
ISET
VDR
FB
LX
VREF
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 controller resets internal soft start circuit.
Ground pin.
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.
Internal P-Channel FET Source. Connect to input voltage.
Input power supply for the controller. Place input decoupling capacitor as close as
possible to this pin. Connect to input voltage.
Internal P-Channel FET Drain. Connect to the output inductor.
This pin is used as a current limit input for the internal current limit comparator. Connect
to LX 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
Error Amplifier
= 300mV – 30uA * R. Where R≤3kΩ
200ms delay
+
-
VIN
I = k x VIN
UVLO
Oscillator
Set Dominant
PWM Comparator
FAULT
Register
S
R
R
3
+
-
POR
DESCRIPTION
4-Bit counter
FAULT
CONVERTER BLOCK DIAGRAM
PWM Latch
Reset Dominant
S
R
R
ENBL
SVIN
Overcurrent
Comparator
Vin - 5V LDO
5V Internal LDO
-
+
Copyright 2008 EXAR Corporation
VIN - 0.3V
VDR
FET GATE
Internal
P-FET
30uA
Power PAD
GND
VDR
PVIN
ISET
LX