CS5165A

http://onsemi.com

11

Figure 17. Output Voltage Transient Response to a 14

Trace 1− GATE(H) (10 V/div.)

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

Trace 3− Load Current (5.0 A/div)

PROTECTION AND MONITORING FEATURES

Short Circuit Protection

A lossless hiccup mode short circuit protection feature is

provided, requiring only the Soft−Start capacitor to implement.

the FAULT latch. This causes the top FET to shut off,

disconnecting the regulator from it’s input voltage. The

Soft−Start capacitor is then slowly discharged by a 2.0

mA

current source until it reaches it’s lower 0.7 V threshold. The

regulator will then attempt to restart normally, operating in it’s

extended off time mode with a 50% duty cycle, while the

Soft−Start capacitor is charged with a 60

mA charge current.

If the short circuit condition persists, the regulator output

before the Soft−Start capacitor is charged to it’s upper 2.5 V

threshold. If this happens the cycle will repeat itself until the

short is removed. The Soft−Start charge/discharge current

ratio sets the duty cycle for the pulses (2.0

mA/60 mA = 3.3%),

while actual duty cycle is half that due to the extended off time

mode (1.65%).

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 18

and 19).

If the short circuit condition is removed, output voltage will

rise above the 1.0 V level, preventing the FAULT latch from

being set, allowing normal operation to resume.

Figure 18. Demonstration Board Hiccup Mode Short

Circuit Protection. Gate Pulses are Delivered While

the Soft−Start Capacitor Charges, and Cease During

Discharge

M 25.0 ms

Trace 3− Soft−Start Timing Capacitor (1.0 V/div.)

Trace 4− 5.0 V Supply Voltage (2.0 V/div.)

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

Figure 19. Demonstration Board Startup with

Regulator Output Shorted To Ground

M 50.0

ms

Trace 4− 5.0 V from PC Power Supply (2.0 V/div.)

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

Overvoltage Protection

Overvoltage protection (OVP) is provided as result of the

additional external components. The control loop responds to

an overvoltage condition within 100 ns, causing the top

MOSFET to shut off, disconnecting the regulator from it’s

input voltage. The bottom MOSFET is then activated, resulting

in a “crowbar” action to clamp the output voltage and prevent

damage to the load (see Figures 20 and 21 ). The regulator will