CS5151 Просмотр технического описания (PDF) - Cherry semiconductor

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CS5151

CPU 4-Bit Nonsynchronous Buck Controller

Cherry semiconductor 

Applications Information: continued

components, input power supply, and PC board traces

than occurs with constant current limit protection (see

Figures 10 and 11).

If the short circuit condition is removed, output voltage

will rise above the 1V level, preventing the FAULT latch

from being set, allowing normal operation to resume.

External Output Enable Circuit

On/off control of the regulator can be implemented

through two additional discrete components (see Figure 12).

This circuit operates by pulling the soft start pin high, and

the VFFB pin low, emulating a short circuit condition.

5V

Shutdown

Input

MMUN2111T1 (SOT-23)

IN4148

5 SS

CS5151

8 VFFB

Trace 4 - 5V Supply Voltage (2V/div.)

Trace 3 - Soft Start Timing Capacitor (1V/div.)

Trace 2 - Inductor Switching Node (2V/div.)

Figure 10: CS5151 demonstration board hiccup mode short circuit pro-

tection. Gate pulses are delivered while the soft start capacitor charges,

and cease during discharge.

Figure 12: Implementing shutdown with the CS5151.

External Power Good Circuit

An optional Power Good signal can be generated through

the use of four additional external components (see Figure

15). The threshold voltage of the Power Good signal can be

adjusted per the following equation:

(R1 + R2) × 0.65V

VPower Good =

R2

This circuit provides an open collector output that drives

the Power Good output to ground for regulator voltages

less than VPower Good.

Trace 4 = 5V from PC Power Supply (2V/div.)

Trace 2 = Inductor Switching Node (2V/div.)

R1

10k

VOUT

CS5151

5V

R3

10k

PN3904

R2

6.2k

Power Good

PN3904

Figure 11: Startup with regulator output shorted.

Overvoltage Protection

Overvoltage protection (OVP) is provided as result of the

normal operation of the V2™ control topology and requires

no additional external components. The control loop

responds to an overvoltage condition within 100ns, causing

the MOSFET to shut off, disconnecting the regulator from

its input voltage.

Figure 13: Implementing Power Good with the CS5151.

9

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