RT7248
Function Block Diagram
VIN
Internal
Regulator
Shutdown
V
A
V
CC
Comparator
1.2V
+
-
Lockout
Comparator
-
2.5V +
V
CC
6µA
SS
0.923V
+
+
-
Error Amp
COMP
0.4V
Oscillator
Slope Comp
Foldback
Control
+
-
UV
Comparator
Current Sense
Amplifier
+
-
R
SENSE
V
A
BOOT
S
+
-
Current
Comparator
R
Q
Q
150mΩ
EN
5kΩ
SW
130m
Ω
GND
FB
Operation
Shutdown Comparator
Activate internal regulator once EN input level is larger
than the target level. Force IC to enter shutdown mode
when the EN input level is lower than 0.4V.
Internal Regulator
Provide internal power for logic control and switch gate
drivers.
Lockout Comparator
Activate the Current Comparator, release lock-out logic,
and enable the switches as EN input level is larger than
lockout voltage. Otherwise, the switches still locks out.
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.
UV Comparator
As FB voltage is lower than the UV voltage, it will activate
a UV protect scheme.
Error Amp
The output voltage COMP of the error amplifier is adjusted
comparing FB signal with the internal reference voltage
and SS signal.
Current Sense Amplifier
R
SENSE
detects the peak current of the high-side switch.
This signal is amplified by the Current Sense Amplifier
and added with a Slope Compensation. Then, it controls
the switches by comparing this signal with the COMP
voltage.
Copyright
©
2012 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS7248-01
September 2012
www.richtek.com
3
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
