Data Sheet

WPMDH1152401 / 171012402
MagI
3
C Power Module
VDRM – Variable Step Down Regulator Module
we-online.com Würth Elektronik eiSos GmbH & Co. KG – Data Sheet Rev. 2.0
© December 2017
16/54
BLOCK DIAGRAM
C
OUT
LSS
HSS
RON
VIN
EN PGND
SS
FB
VOUT
15µH
C
VCC
C
BST
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
V
REF
0.8V
Comparator
CIRCUIT DESCRIPTION
The MagI³C Power Module 171012402 is based on a synchronous step-down regulator with integrated MOSFETs 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 by 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 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 V
IN
variations,
(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.
The 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 171012402 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 around 10mV (similar to current or voltage mode devices) are
achieved.