ACT4524_16 datasheet(5/16 Pages) ACTIVE-SEMI

5 / 16 page

ACT4524

Rev 1.1, 22-Feb-16

Innovative PowerTM

- 5 -

www.active-semi.com

FUNCTIONAL BLOCK DIAGRAM

PWM

Controller

Driver

Current Sense

and Control

70mΩ

4.7Ω

OVP

CSP

CSN1

CSN2

GND

HSB

UVLO

VIN

CLK

MODE

FUNCTIONAL DESCRIPTION

Output Current Sensing and Regulation

The conventional cycle-by-cycle peak current mode

is implemented with high-side FET current sense.

Sense resistors are connected to the channel 1 and

channel 2 outputs, respectively. The sensed

differential voltage is compared with interval

reference to regulate current. CC loop and CV loop

are in parallel. The current loop response is allowed

to have slower response compared to voltage loop.

However, during current transient response, the

inductor current overshoot/undershoot should be

controlled

within

+/-25%

avoid

inductor

saturation.

Input Over Voltage Protection

The converter is disabled if the input voltage is

above 42V (+/-2V). Device resumes operation

automatically 40ms after OVP is cleared.

Output Over Voltage Protection

Device stops switching when output over-voltage is

sensed, and resumes operation automatically when

output voltage drops to OVP- hysteresis.

Output Under-Voltage Protection /

Hiccup Mode

There is a under voltage protection (UVP)

threshold. If the UVP threshold is hit for 10us, an

over current or short circuit is assumed, and the

converter goes into hiccup mode by disabling the

converter and restarts in 4 seconds and restarts.

Cord Compensation

In some applications, the output voltage is

increased with output current to compensate the

potential voltage drop across output cable. The

compensation is based on the high side feedback

resistance.

For ACT4524, the compensation voltage can be

derived as:

ΔVout = RCS* IO*K

Where RCS is the VOUT1 current resistance, IO is the

output current, and K is the cord compensation

factor. This voltage difference could be added on

the reference or turning the (VCSP-VCSN) voltage into

a sink current at FB pin to pull Vout higher than

programmed voltage.

The cord compensation loop should be very slow to

avoid potential disturbance to the voltage loop. The

voltage loop should be sufficiently stable on various

cord compensation setting.

Thermal Shutdown

If the TJ increases beyond 160°C, ACT4524 goes

into HZ mode and the timer is preserved until TJ

drops by 30°C.

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