CS5150H View Datasheet(PDF) - Cherry semiconductor

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CS5150H

High Performance/ Integrated Current Mode PWM Controllers

Cherry semiconductor 

Applications Information: continued

This protection feature results in less stress to the regulator

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.

ed, resulting in a “crowbar” action to clamp the output

voltage and prevent damage to the load (see Figures 12 and

13). The regulator will remain in this state until the over-

voltage condition ceases or the input voltage is pulled low.

The bottom FET and board trace must be properly

designed to implement the OVP function.

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

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

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

Figure 10: CS5150H demonstration board hiccup mode short circuit pro-

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

and cease during discharge.

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

Trace1 = Regulator Output Voltage (1V/div.)

Trace 2 = Inductor Switching Node (5V/div.)

Figure 12: OVP response to an input-to-output short circuit by immedi-

ately providing 0% duty cycle, crow-barring the input voltage to

ground.

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

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

Figure 11: Startup with regulator output shorted.

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

Trace 1 = Regulator Output Voltage (1V/div.)

Figure 13: OVP response to an input-to-output short circuit by pulling

the input voltage to ground.

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 top MOSFET to shut off, disconnecting the regulator

from its input voltage. The bottom MOSFET is then activat-

External Output Enable Circuit

On/off control of the regulator can be implemented

through the addition of two additional discrete compo-

nents (see Figure 14). This circuit operates by pulling the

soft start pin high, and the VFFB pin low, emulating a short

circuit condition.

9

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