EA4524YH Datasheet, PDF (5/16 Pages) Active-Semi, Inc – 40V/3.5A Buck Converter with Dual Output and Separated Over Current Protection

FUNCTIONAL BLOCK DIAGRAM
VIN
UVLO
CLK
PWM
Controller
MODE
OVP
Current Sense
and Control
HSB
Driver
ACT4524
Rev 1.1, 22-Feb-16
70mΩ
SW
4.7Ω
CSP
CSN1
CSN2
GND
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% to 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 = R_CS* I_O*K
Where R_CS is the V_OUT1 current resistance, I_O is the
output current, and K is the cord compensation
factor. This voltage difference could be added on
the reference or turning the (V_CSP-V_CSN) 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 T_J increases beyond 160°C, ACT4524 goes
into HZ mode and the timer is preserved until T_J
drops by 30°C.
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