AP22652/AP22653/AP22652A/AP22653A

Document number: DS41186 Rev. 3 - 2

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AP22652/AP22653/AP22652A/AP22653A

Application Information (continued)

Current-Limit Threshold Programming

The current-limit threshold can be programmed using an external resistor. The current-limit threshold is proportional to the current sourced out of

ILIM.

The recommended 1% resistor range for RLIM is 10kΩ ≤ RLIM ≤ 210kΩ. Figure 14 includes current-limit tolerance due to variations caused by

temperature and process. This graph does not include the external resistor tolerance. The traces routing the RLIM resistor to the AP22652/52A

and AP22653/53A should be as short as possible to reduce parasitic effects on the current-limit accuracy.

To design below a maximum current-limit threshold, find the intersection of RLIM and the maximum desired load current on the IOS(max) (ILIM) curve

and choose a value of RLIM above this value. Programming the current limit below a maximum threshold is important to avoid current limiting

upstream power supplies causing the input voltage bus to drop. The resulting minimum current-limit threshold is the intersection of the selected

value of RLIM and the IOS(min) (ILIM) curve.

Best-Fit Current-Limit Threshold Equations (ILIMIT):

ILIMIT_Min[mA] = 28955/R[kΩ]1.075

ILIMIT_Typ[mA] = 30321/R[kΩ]1.055

ILIMIT_Max[mA] = 31033/R[kΩ]1.031

Figure 14. Current-Limit Threshold vs. RLIM

Thermal Protection

Thermal protection prevents the IC from damage when the die temperature exceeds safe margins. This mainly occurs when heavy-overload or

short-circuit faults are present for extended periods of time. The AP22652/52A and AP22653/53A implement a thermal sensing to monitor the

operating junction temperature of the power distribution switch. Once the die temperature rises to approximately +145°C, the thermal protection

feature activates as follows: The internal thermal sense circuitry turns the power switch off and the FAULT output is asserted, thus preventing the

power switch from damage. Hysteresis in the thermal sense circuit allows the device to cool down by approximately +40°C before the output is

turned back on. This built-in thermal hysteresis feature is an excellent feature, as it avoids undesirable oscillations of the thermal protection circuit.

Reverse-Current and Reverse-Voltage Protection

The USB specification does not allow an output device to source current back into the USB port. In a normal MOSFET switch, current will flow in

reverse direction (from the output side to the input side) when the output side voltage is higher than the input side. A reverse-current limit (ROCP)

feature is implemented in the AP22652/52A and AP22653/53A to limit such back currents. The ROCP circuit is activated when the output voltage

is higher than the input voltage. After the reverse current circuit has tripped (reached the reverse current trip threshold), the current is clamped at

this IROCP level.

In addition to ROCP, reverse overvoltage protection (ROVP) is also implemented. The ROVP circuit is activated by the reverse voltage

comparator trip point; i.e., the difference between the output voltage and the input voltage.

For AP22652/53, once ROVP is activated, FAULT assertion occurs at a de-glitch time of 6ms. Recovery from ROVP is automatic when the fault is

removed. FAULT de-assertion de-glitch time is same as the de-assertion time.

For AP22652A/53A, once ROVP is activated and when the condition exists for more than 5ms (typ), output device is disabled and shut down. This

is called the "Time from Reverse-Voltage Condition to MOSFET Turn Off". FAULT assertion occurs at a de-glitch time of 6ms after ROVP is

reached. Recovery from this fault is achieved by recycling power or toggling EN. FAULT de-assertion de-glitch time is same as the de-assertion

time.

RLIM Current-Limit Programming Resistor (kΩ)

VIN=5V

ILIM(typ)

ILIM(max)

ILIM(min)