RT7296F

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is a registered trademark of Richtek Technology Corporation.

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DS7296F-06

September

2023

4

Undervoltage Lockout Threshold

The IC includes an input Undervoltage Lockout

Protection (UVLO). If the input voltage exceeds the

UVLO rising threshold voltage (3.9V), the converter

resets and prepares the PWM for operation. If the input

voltage falls below the UVLO falling threshold voltage

(3.25V) during normal operation, the device stops

switching. The UVLO rising and falling threshold

voltage includes a hysteresis to prevent noise caused

reset.

Chip Enable

The EN pin is the chip enable input. Pulling the EN pin

low (<1.1V) will shutdown the output voltage. During

shutdown mode (<0.4V), the RT7296F

’s quiescent

current drops to lower than 1

A. Driving the EN pin

high (>1.6V) will turn on the device.

Operating Frequency and Synchronization

The internal oscillator runs at 500kHz (typ.) when the

EN/SYNC pin is at logic-high level (>1.6V). If the EN

pin is pulled to low-level over 8

s, the IC will shut down.

The RT7296F can be synchronized with an external

clock ranging from 200kHz to 2MHz applied to the

EN/SYNC pin. The external clock duty cycle must be

from 20% to 80% with logic-high level = 2V and

logic-low level = 0.8V.

Internal Regulator

The internal regulator generates 5V power and drive

internal circuit. When VIN is below 5V, PVCC will drop

with VIN. A capacitor (>0.1

F) between PVCC and

GND is required.

Internal Soft-Start Function

The RT7296F provides internal soft-start function. The

soft-start function is used to prevent large inrush

current while converter is being powered-up. Output

voltage starts to rise 1.2ms after EN rising, and the

soft-start time (VFB from 0V to 0.8V) is 1.5ms. PG signal

goes high 0.8ms after completing soft-start.

VOUT

EN

VIN

PG

VIN = 12V

VCC = 5V

VCC

1.2ms

1.5ms

0.8ms

High-Side MOSFET Overcurrent Limit

The RT7296F features cycle-by-cycle current-limit

protection

and

prevents

the

device

from

the

catastrophic damage in output short circuit, overcurrent

or inductor saturation. During the on-time of the high

side switch, the device monitors the switch current. If

the switch current overs the current-limit threshold, the

device turns off the high side switch to prevent the

device from damage.

Output Undervoltage Protection

The RT7296F includes output undervoltage protection

(UVP) against over-load or short-circuited condition by

constantly monitoring the feedback voltage VFB. If VFB

drops below the undervoltage protection trip threshold,

50% (typ.) of the internal reference voltage, the UV

comparator will go high to turn off the internal high-side

MOSFET switches. If the output undervoltage condition

continues for a period of time, the RT7296F will enter

output undervoltage protection with hiccup mode.

During hiccup mode, the device remains shut down.

After a period of time, a soft-start sequence for

auto-recovery will be initiated. Upon completion of the

soft-start sequence, if the fault condition is removed,

the converter will resume normal operation; otherwise,

such cycle for auto-recovery will be repeated until the

fault condition is cleared. Hiccup mode allows the

circuit to operate safely with low input current and

power dissipation, and then resume normal operation

as soon as the over-load or short-circuit condition is

removed. The UVP profile is shown in Figure 2.