ST EVAL-RHRICL1AFV1, User Manual, Page: 20 / 27

where:
•
V
F
is the output voltage of V/I characteristic of Figure 20. Foldback current limiter characteristic (0 V in case
of a short-circuit condition)
• “I
RS
“ is a design parameter referring to the input current of the current sense amplifier, having a typical value
of 500 μA
• R=RS3+=RS3-
• I
FLB
is the current flowing through the foldback resistor R
FLB
and whose value is given by:
IFLB =
VCC − VF − R*I − 0.1
RFLB
(11)
Of course, in case of output short-circuit condition, V
F
= 0 V and I = I
F
, i.e. the small and safe value (see
Figure 20. Foldback current limiter characteristic ) reached when a short-circuit on the load side occurs and
persists.
The
Eq. (10) and Eq. (11) are intended as a theoretical support to estimate the foldback current I (or IF) and do
not take into account the variation due to external component accuracy and matching, as well as the standard
process variations. Trimming on the final application is necessary.
In order to obtain the best results, it is recommended to use well-matched high precision resistors (0.1%) for
RS3+ and RS3- and R
FLB
.
The typical behavior of the device configured in latched mode is depicted below (timing is not in scale).
Figure 21. Foldback mode diagram
UM2605
Getting started
UM2605 - Rev 1
page 20/27