ACT4524
Rev 1.1, 22-Feb-16
FUNCTIONAL BLOCK DIAGRAM
HSB
VIN
PWM
Controller
UVLO
70mΩ
CLK
SW
Driver
MODE
4.7Ω
Current Sense
and Control
OVP
CSN2
CSP
CSN1
GND
FUNCTIONAL DESCRIPTION
converter goes into hiccup mode by disabling the
converter and restarts in 4 seconds and restarts.
Output Current Sensing and Regulation
The conventional cycle-by-cycle peak current mode
is implemented with high-side FET current sense.
Cord Compensation
Sense resistors are connected to the channel 1 and
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.
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% to avoid inductor
saturation.
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.
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.
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.
Output Over Voltage Protection
Device stops switching when output over-voltage is
sensed, and resumes operation automatically when
output voltage drops to OVP- hysteresis.
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.
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
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