CS5157H データシートの表示（PDF） - ON Semiconductor

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CS5157H

CPU 5−Bit Synchronous Buck Controller

ON Semiconductor 

CS5157H

M 250 ms

Trace 1− Regulator Output Voltage (1.0 V/div.)

Trace 2− Inductor Switching Node (2.0 V/div.)

Trace 3− 12 V Input (VCC1 and VCC2) (5.0 V/div.)

Trace 4− 5.0 V Input (1.0 V/div.)

Figure 4. CS5157H Demonstration Board Startup in

Response to Increasing 12 V and 5.0 V Input Voltages.

Extended Off Time is Followed by Normal Off Time

Operation when Output Voltage Achieves Regulation to

the Error Amplifier Output.

M 10.0 ms

Trace 1− Regulator Output Voltage (5.0 V/div.)

Trace 2− Inductor Switching Node (5.0 V/div.)

Figure 6. CS5157H Demonstration Board Enable

Startup Waveforms

Normal Operation

During normal operation, switch off time is constant and

set by the COFF capacitor. Switch on time is adjusted by the

V2 control loop to maintain regulation. This results in

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).

M 2.50 ms

Trace 1− Regulator Output Voltage (1.0 V/div.)

Trace 3− COMP PIn (error amplifier output) (1.0 V/div.)

Trace 4− Soft−Start Pin (2.0 V/div.)

Figure 5. CS5157H Demonstration Board Startup

Waveforms

If the input voltage rises quickly, or the regulator output

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).

M 1.00 ms

Trace 1− Regulator Output Voltage (10 mV/div.)

Trace 2− Inductor Switching Node (5.0 V/div.)

Figure 7. Peak−to−Peak Ripple on VOUT = 2.8 V,

IOUT = 0.5 A (Light Load)

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