RT7237C
Function Block Diagram
VIN
Internal
Regulator
Oscillator
Current Sense
Amplifier
Slope Comp
Shutdown
Comparator
V
V
CC
A
+
V
A
Foldback
R
SENSE
-
Control
1.2V
+
-
0.4V
+
BOOT
SW
Lockout
Comparator
-
S
Q
Q
150mΩ
130mΩ
UV
5kΩ
Comparator
-
EN
+
R
-
+
1.8V
Current
GND
Comparator
V
CC
6µA
0.8V
+
+
-
EA
SS
FB
COMP
Operation
UV Comparator
Internal Regulator
As FB voltage is lower than the UV voltage, it will activate
a UV protect scheme.
Provide internal power for logic control and switch gate
drivers.
Error Amplifier
Shutdown Comparator
The output voltage COMP of the error amplifier is adjusted
by comparing FB signal with the internal reference voltage
and SS signal.
Activate internal regulator once EN input level is higher
than the target level. Force IC to enter shutdown mode
when the EN input level is lower than 0.4V.
Current Sense Amplifier
Lockout Comparator
R
SENSE detects the peak current of the high side switch.
Activate the current comparator, release lock-out logic,
and enable the switches as EN input level is higher than
lockout threshold voltage. Otherwise, the switches still
lock out.
This signal is amplified by the current sense amplifier and
added with a slope compensation signal. Then, It controls
the switches by comparing this signal with the COMP
voltage.
Oscillator
The oscillator provides internal clock and controls the
converter's switching frequency.
Foldback Control
Dynamically adjust the internal clock. It provides a slower
frequency as a lower FB voltage.
Copyright 2012 Richtek Technology Corporation. All rights reserved.
©
is a registered trademark of Richtek Technology Corporation.
DS7237C-04 November 2012
www.richtek.com
3
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
