Datasheet

we-online.com
© May 2016
Würth Elektronik eiSos GmbH & Co. KG - Data Sheet - REV 1.0
24/46
WPMDU1251501 / 171021501
MagI³C Power Module
VDRM - Variable Step Down Regulator Module
Step 6 Optional: Program undervoltage lockout divider (R
UVLO1
and R
UVLO2
)
The function of the R
UVLO1
and R
UVLO2
divider is to allow the designer to choose an input voltage below which the circuit
will be disabled. This implements the feature of programmable external undervoltage lockout.
This is often used in battery powered systems to prevent deep discharge of the system battery. It is also useful in system
designs for sequencing of output rails or to prevent early turn-on of the supply as the main input voltage rail rises at power-
up. Most systems will benefit by using the precision Enable threshold to establish a system undervoltage lockout. The
recommended approach is to choose an input UVLO level higher than the target regulated output voltage for the stage.
EN/UVLO
VIN
AGNDINTSS
26
V
IN
27
29
Figure 5. EN/UVLO configuration without resistive divider
Without an Enable divider (Figure 5), this MagI³C Power Module will attempt to turn on around 2.5V (V
UVLO
voltage threshold
referenced to V
IN
pin26). This would not be useful for a stage that ultimately might be creating 5Vout. Operation of the
module on input voltage conditions below the nominal output should be avoided. Systems that don't implement the Enable
divider will turn in early during the rise of Vin and might not have monotonic rise in output voltage. Many systems need
smooth rise in supply voltage. In the case of sequencing supplies, the divider is connected to a rail that becomes active
earlier in the power-up cycle than the MagI³C power module output rail.
EN/UVLO
VIN
AGND
R
UVLO1
R
UVLO2
INTSS
26
V
IN
27
29
Figure 6. Undervoltage Lockout (UVLO) Schematic
Using the external enable divider R
UVLO1
and R
UVLO2
as shown in Figure 6, the designer is able to precisely select the turn-
on and turn-off thresholds of this MagI³C Power Module. At turn-on, the V
ON
UVLO threshold determines the input voltage
level where the device begins power conversion. During the power-down sequence, the V
OFF
UVLO threshold determines
the input voltage where power conversion ceases.