RHFL4913A Datasheet, PDF (11/20 Pages) STMicroelectronics – Rad-hard adjustable positive voltage regulator

RHFL4913A
Application information
parasitic voltage, resistor RW1can be introduced to provide the necessary compensating
voltage signal to the ADJUST pin.
6.3
FPGA power supply lines
Because these devices are very sensitive to V_DD transients beyond a few % of their nominal
supply voltage (usually 1.5 V), special attention must be given by supply lines designers to
mitigate possible heavy ion L4913 disturbances. The worst case heavy ion effect can be
summarized as: the L4913 internal control loop being cut (made open) or short-circuited for
a sub-microsecond duration. During such an event, the L4913 die power element can either
provide excessive current or current supply stoppage to the output (V_OUT) for a duration of
about one microsecond, after which time the L4913 smoothly recovers to nominal operation.
To mitigate these "transients", it is recommended to implement the L4913 PCB layout as
follows:
● Minimizing series/parallel parasitic inductances of the PC path
● Using a low ESR 47 µF Tantalum V_OUT filtering capacitor with a 470 nF ceramic
capacitor in parallel with the former (to reduce dynamic ESR)
● Inserting a 100-200 nH ferrite core on the V_OUT-to-tantalum capacitor wire
With this implementation, the ELDO simulated worst transient case shows no more than 90
mV deviation from the nominal line voltage value.
Doc ID 10005 Rev 11
11/20