Applications Information: continued

9

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.

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 11: Startup with regulator output shorted.

Overvoltage Protection

Overvoltage protection (OVP) is provided as result of the

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.

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

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:

This circuit provides an open collector output that drives

the Power Good output to ground for regulator voltages

Figure 13: Implementing Power Good with the CS5151.

CS5151

R1

10k

R2

6.2k

R3

10k

Power Good

5V

PN3904

PN3904

(R1 + R2) × 0.65V

R2

Shutdown

Input

5V

CS5151

SS

5

8

IN4148

MMUN2111T1 (SOT-23)

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

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

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

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

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