APW7252 datasheet(18/24 Pages) ANPEC

18 / 24 page

Rev. A.1 - Dec., 2016

APW7252

www.anpec.com.tw

Function Description

Under-Voltage Lockout

An under-voltage lockout function prevents the device from

operating if the input voltage on VIN is lower than approxi-

mately 2.4V. The device automatically enters the shut-

down mode if the voltage on VIN drops below approxi-

mately 2.2V. This under-voltage lockout function is imple-

mented in order to prevent the malfunctioning of the

converter.

Soft-start

The APW7252 has a built-in digital soft-start to control the

rise rate of the output voltage and limit the input current

surge during start-up. During soft-start, the reference

voltage, output from a DAC, raises up step by step to

control the output voltage to rise gently.

Frequency Modulation Mode (PFM)

The APW7252

’s boost converter and negative charge

pump will automatically enter in PFM mode operation to

reduce the dominant switching losses. These controls

get low quiescent current, help to maintain high efficiency

over the complete load range.

Over-Temperature Protection (OTP)

The over-temperature circuit limits the junction tempera-

ture of the APW7252. When the junction temperature ex-

ceeds 160oC, a thermal sensor turns off the both power

MOSFET

’s, allowing the devices to cool. The thermal sen-

sor allows the converters to start a soft-start process and

regulate the output voltage again after the junction tem-

perature cools by 10oC. The OTP designed with a 10oC

hysteresis lowers the average Junction Temperature (T

during continuous thermal overload conditions, increas-

ing the life time of the device.

Under Voltage Protection (UVP)

The under-voltage protection circuit monitors the outputs

to protect the device against short-circuit or heavy load

conditions. When one of the output voltages is falls be-

low the UVP threshold (50% of VREF), a fault signal is

generated and the device turns off all outputs. The device

is then latched off and will initials a soft-start process

until re-cycle ENP and ENN or VIN.

Over Current Protection (OCP)

The APW7252 monitors the output current of the boost

converter, flowing through the N-Channel power MOSFET,

and limits the IC from damages during overload, short-

circuit and over-voltage conditions.

Enable and Shutdown

Driving ENP and ENN to ground turns off the VP and VN

voltage respectively. When both ENN and ENP is in logic

low state, the boost converter is also enters shutdown

mode and VIN quiescent supply current reduces to less

than 3

µA.

Discharge Resistance Enable/Disable

APW7252 Discharge resistance function always turn on

condition are ENN and ENP were setting low when input

voltage is high than POR. secondly, the input voltage is

low than POR then that

’s always turn on no matter ENN

and ENP were setting high or low states. The indepen-

dent discharge function of V

OUTP and VOUTN can be by DISP

bit and DISN bit. If the V

OUTP and VOUTN were normal opera-

tion then Discharge resistance function was disabling.

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