IC-DC_17 Datasheet, PDF (15/19 Pages) IC-Haus GmbH – 2-CHANNEL BUCK/BOOST DC/DC CONVERTER

iC-DC
2-CHANNEL BUCK/BOOST DC/DC CONVERTER
ERROR EVALUATION
Rev B1, Page 15/19
Supply voltage monitor
Supply voltage VBR is monitored. If the normal volt-
age range is overshot or undershot, this is signaled at
open-drain pin VBROK. The bias current generated by
an external reference resistor is also monitored and an
error signaled at VBROK should the permissible range
be exceeded. If an error has occurred, pin VBROK is
switched to GND.
Output voltage monitor
The two linear regulator output voltages VCC1 and
VCC2 are also monitored. If the overvoltage threshold
is overshot or the undervoltage threshold undershot
(e.g. due to overload), a message is generated at the
current-limited push-pull outputs V1OK and V2OK. Volt-
age outputs POE1 and POE2 are shut down.
V2OK. The function of the connected POE1 and POE2
outputs remains unaffected.
Temperature monitor
The internal chip temperature is monitored. If the
monitor indicates overtemperature, all switches on the
switching converter are shut down. These are auto-
matically re-enabled when the chip temperature has
dropped below the restart temperature. A message
is signaled at open-drain pin TOK for as long as the
converter is shut down due to chip overtemperature.
The protective switch (VB / VBR) has its own over
temperature protection, which is also operative during
standby mode.
Output voltage monitor self-test
Using pin TEST the voltage monitoring comparators at
V1OK and V2OK can be tested during ongoing opera-
tion. The undervoltage and overvoltage thresholds of
V1OK and V2OK are checked in turn with each test.
For this purpose, pin TEST is increased to above the
threshold voltage by an external driver. Correct func-
tioning is signaled by low signals at pins V1OK and
As error outputs VBROK and TOK are current limited,
an LED can be directly connected up for visual mes-
sage display. However, the additional power dissipation
this causes in the IC must be taken into account. By
placing resistor R_LED in series with the LED, this ad-
ditional chip power loss can be reduced in the event
of error. CMOS or TTL-compatible logic inputs can be
activated by pull-up resistors at VBROK and TOK.
AUTARKY FUNCTION
By inserting a capacitor at VBR, an Autarky function can
be realized should the supply fail at VB. This Autarky
function guarantees the linear regulator output voltages
for some time. If the voltage at VBR is greater than at
VB (elec. char. no. 109), this is signaled by current-lim-
ited open-drain output NAUT. To ensure that VBR > VB
should the supply voltage fail, it is recommended that a
resistor be switched between VB and GND in order to
generate the required differential voltage of d_{VBR, VB}.
With this capacitor acting as a buffer, the effect of cur-
rent spikes feeding back into the supply voltage VB is
also reduced.