cs5157h ON Semiconductor, cs5157h Datasheet - Page 8

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

is enabled externally, output voltage will increase to the
level set by the error amplifier output more rapidly, usually
within a couple of cycles (see Figure 6).
Operation when Output Voltage Achieves Regulation to
Response to Increasing 12 V and 5.0 V Input Voltages.
Trace 3− COMP PIn (error amplifier output) (1.0 V/div.)
Trace 4− Soft−Start Pin (2.0 V/div.)
Trace 1− Regulator Output Voltage (1.0 V/div.)
If the input voltage rises quickly, or the regulator output
Figure 4. CS5157H Demonstration Board Startup in
Trace 1− Regulator Output Voltage (1.0 V/div.)
Trace 2− Inductor Switching Node (2.0 V/div.)
Trace 3− 12 V Input (V
Trace 4− 5.0 V Input (1.0 V/div.)
Extended Off Time is Followed by Normal Off Time
Figure 5. CS5157H Demonstration Board Startup
the Error Amplifier Output.
CC1
and V
Waveforms
M 2.50 ms
CC2
M 250 ms
) (5.0 V/div.)
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CS5157H
8
Normal Operation
set by the C
V
changes in regulator switching frequency, duty cycle, and
output ripple in response to changes in load and line. Output
voltage ripple will be determined by inductor ripple current
working into the ESR of the output capacitors (see Figures
7 and 8).
2
During normal operation, switch off time is constant and
Trace 1− Regulator Output Voltage (5.0 V/div.)
Trace 2− Inductor Switching Node (5.0 V/div.)
Trace 2− Inductor Switching Node (5.0 V/div.)
Trace 1− Regulator Output Voltage (10 mV/div.)
Figure 6. CS5157H Demonstration Board Enable
control loop to maintain regulation. This results in
Figure 7. Peak−to−Peak Ripple on V
OFF
capacitor. Switch on time is adjusted by the
I
OUT
Startup Waveforms
= 0.5 A (Light Load)
M 1.00 ms
M 10.0 ms
OUT
= 2.8 V,