RT7251A/B
Functional Pin Description
Pin No.
Pin Name
Pin Function
1
2
SW
Switch Node. Connect to external L-C filter.
VIN
Input Supply Voltage. Must bypass with a suitably large ceramic capacitor.
Bootstrap for High Side Gate Driver. Connect 0.01μF or greater ceramic
capacitor from BOOT to SW pin.
3
4
BOOT
Chip Enable. A logic-high enables the converter; a logic-low forces the
RT7251A/B into shutdown mode, reducing the supply current to less than 5μA.
Attach this pin to VIN with a 100kΩ pull up resistor for automatic startup.
EN
Feedback Input Pin. For an adjustable output, connect an external resistive
voltage divider to this pin.
5
6
FB
Power Good Indicator. The output of this pin is low if the output voltage is
12.5% less than the nominal voltage. Otherwise, it is an open drain.
PGOOD
GND
7, 8,
9 (Exposed Pad)
Ground. The exposed pad must be soldered to a large PCB and connected to
GND for maximum power dissipation.
Function Block Diagram
VIN
Internal
Regulator
OSC
340kHz/800kHz
Enable
Comparator
V
V
CC
A
Slope Comp
+
-
+
-
2.5V
Current Sense
Amplifier
Foldback
Control
EN
5k
V
3V
1V
A
+
-
BOOT
SW
OV
145m
140m
S
R
Q
Q
OV Comparator
+
-
+
0.4V
0.8V
UV
-
Current
Comparator
UV Comparator
+
FB
-
Error Amp
PGOOD
GND
Comparator
35pF
400k
0.7V
FB
+
-
1pF
PGOOD
Copyright 2012 Richtek Technology Corporation. All rights reserved.
©
is a registered trademark of Richtek Technology Corporation.
DS7251A/B-01 April 2012
www.richtek.com
3
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
