AP72250

Document number: DS44135 Rev. 1 - 2

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AP72250

Application Information (continued)

4

Power-Good (PG) Indicator

The PG pin of AP72250 is an open-drain output that is actively held low during the soft-start period until the output voltage reaches 80% of its target

value. When the output voltage is outside of its regulation by +20% or -25%, PG pulls low until the output returns within +15% or -20% of its set

value. The PG rising edge transition is delayed by 2ms while its falling edge transition is delayed by 5

μs to prevent false triggering. The PG pin is

connected to an internal VCC

through an internal 5MΩ pull-up resistor.

5

Undervoltage Lockout (UVLO)

Undervoltage lockout is implemented to protect the IC from insufficient input voltages. The AP72250 disables if the input voltage falls below 0.57V.

In this UVLO event, both the high-side and low-side power MOSFETs turn off and the 200

Ω active discharge enables to discharge the output voltage

to ground.

6

Overcurrent Protection (OCP) and Short-Circuit Protect (SCP)

The AP72250 has cycle-by-cycle peak current limit protection by sensing the current through the internal low-side power MOSFET, Q1. While Q1

is on, the internal sensing circuitry monitors its conduction current. The overcurrent limit has a corresponding voltage limit, VLIMIT. When the voltage

between PGND and SW is lower than VLIMIT due to excessive current through Q1, the OCP triggers, and the controller turns off Q1. During this

time, both Q1 and Q2 remain off. A new switching cycle begins only when the voltage between PGND and SW rises above VLIMIT.

If Q1 consistently hits the peak current limit for seven switching cycles and VOUT < VIN, then the boost converter enters short-circuit protection.

The high-side power MOSFET switches its body diode connection to VIN to protect the device from having a direct path between VIN and VOUT

through the body diode. In the short-circuit condition, the inductor current is regulated at 250mA to prevent excessive power dissipation.

7

Reverse (Negative) Current Protection

During PWM operation, a reverse current comparator on the high-side power MOSFET, Q2, monitors the current entering from VOUT. When this

current exceeds 2A (typical), Q2 turns off for the remainder of the switching cycle. This feature protects the boost converter from excessive reverse

current if the boost output voltage is held above its target voltage by an external source.

8

Output Active Discharge

AP72250

provides an internal 200Ω resistor for the output active discharge function. The internal resistor discharges the energy stored in the output

capacitor to PGND whenever the regulator is disabled or encounters thermal shutdown. The internal discharge resistor disconnects from the output

when the regulator is enabled and in normal operating conditions.

9

Thermal Shutdown (TSD)

If the junction temperature of the device reaches the thermal shutdown limit of +150°C, the AP72250 shuts down both its high-side and low-side

power MOSFETs and triggers the output active discharge. When the junction temperature reduces to the required level (+130°C typical), the device

initiates a normal power-up cycle with soft-start.