cs5157h ON Semiconductor, cs5157h Datasheet - Page 6

• Manufacturer Part Number: cs5157h
• Description: Cpu 5-bit Synchronous Buck Controller
• Manufacturer: ON Semiconductor

COMP
LGnd
V
generated by the ESR of the output capacitors. This ramp is
proportional to the AC current through the main inductor
and is offset by the value of the DC output voltage. This
control scheme inherently compensates for variation in
either line or load conditions, since the ramp signal is
generated from the output voltage itself. This control
scheme inherently compensates for variation in either line or
load conditions, since the ramp signal is generated from the
output voltage itself. This control scheme differs from
traditional techniques such as voltage mode, which
generates an artificial ramp, and current mode, which
generates a ramp from inductor current.
V
V
V
V
V
V
V
V
2
CC1
FFB
SS
ID0
ID1
ID2
ID3
ID4
The V
FB
Control Method
Slow Feedback
Fast Feedback
2
method of control uses a ramp signal that is
3.90 V
3.85V
5 BIT
DAC
+
−
THEORY OF OPERATION
V
Comparator
CC1
Monitor
Error
Amplifier
+
−
1.0 V
PWM
Comparator
PWM COMP
60 mA
2.0 mA
+
−
+
−
V
Comparator
FFB
Low
APPLICATIONS INFORMATION
5.0 V
Figure 2. Block Diagram
2.5 V
http://onsemi.com
CS5157H
0.7 V
Maximum
On−Time
Extended
Off−Time
Off−Time
Timeout
Timeout
Timeout
Normal
6
+
−
+
−
COMP
SS Low
Comparator
SS High
Comparator
Time−Out
(30 ms)
Timer
Figure 3. V
R
S
Off−Time
FAULT
Timeout
Latch
Signal
Ramp
Signal
Error
Q
Q
R
S
FAULT
FAULT
PMW
Latch
+
−
Edge Triggered
PWM
Comparator
C
2
Q
Q
Control Diagram
Amplifier
Error
GATE(H) = ON
GATE(H) = OFF
One Shot
S
R
V
V
C
V
GATE(H)
GATE(L)
OFF
FFB
E
Q
−
+
V
CC1
PGnd
Reference
Output
Voltage
Feedback
V
Voltage
FB
V
PGnd
C
V
V
GATE(H)
OFF
CC2
GATE(L)