Data Sheet

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Würth Elektronik eiSos GmbH & Co. KG - Data Sheet - REV 1.0
10/31
WPMDH1102401 / 171012401
MagI³C Power Module
VDRM - Variable Step Down Regulator Module
BLOCK DIAGRAM
C
OUT
LSS
HSS
R
ON
V
IN
EN PGND
SS
FB
V
OUT
15µH
C
VCC
C
BOOST
0.47µF
Power Module
AGND
Controller/
Power Control/
Protection Circuitry
Linear
Regulator
R
ON
1
2
6
C
SS
5
3 EP4
7
C
IN
R
FBT
R
FBB
C
FF
VIN
UVLO
V
IN
V
OUT
AGND
AGND
CIRCUIT DESCRIPTION
The MagI³C Power Module WPMDH1102401 is based on a synchronous step down regulator with integrated
MOSFET and a power inductor. The control scheme uses a constant on-time (COT) low ripple hysteretic
regulation loop.
The V
OUT
of the regulator is divided with the feedback resistor network R
FBT
and R
FBB
and fed into the FB pin. The
internal comparator compares this signal with the internal 0.8V reference. If the feedback voltage is below the
reference, the High Side MOSFET is turned on for a fixed on-time.
To achieve a regulated output voltage the off-time is modulated. At stable V
IN
to V
OUT
condition the relation
between on-time and off-time is constant. The on-time is fixed and preset by the value of the RON resistor. The
switching frequency is directly proportional to this value.
The connection of the R
ON
resistor to V
IN
results into an additional compensation of varying V
IN
values, (V
IN
feed-
forward) so the switching frequency will remain almost constant even during V
IN
transients.
A load current transient (low to high current) allows the off-time to immediately transition to the minimum of 260
ns. This results in a short term higher switching frequency which ensures an extremely quick regulation response.
As soon as the output capacitor is recharged to the nominal output voltage the switching frequency will return to
the original value even though the load current is higher.
Constant on-time control scheme does not require compensation circuitry which makes the overall design very
simple. Nevertheless it requires a certain minimum ripple at the feedback pin.
The MagI³C Power Module WPMDH1102401 generates this ripple internally and is supported by the C
FF
capacitor which bypasses AC ripple directly to the feedback pin from the output. With this architecture very small
output ripple values of 10ths of millivolts similar to current or voltage mode devices are achieved.