EVAL-AD5100EBZ View Datasheet(PDF) - Analog Devices
Part Name
Description
MFG CO.
EVAL-AD5100EBZ
Analog Devices
'EVAL-AD5100EBZ' PDF : 36 Pages View PDF
MONITORING INPUTS
V1MON
V1MON is a high voltage monitoring input that controls the
SHDN and RESET functions of the external devices. In addition,
it provides a shutdown warning to the system. V1MON monitors
inputs from 6 V to 30 V.
The V1MON pin is monitored by two comparators, one for overvol-
tage and one for undervoltage detection. Both are designed with
1.5% hysteresis.
When the V1MON input goes above the programmed overvoltage
(OV) threshold, the comparator becomes active immediately,
indicating that an OV condition has occurred. Due to hysteresis,
the V1MON input must be brought below the programmed OV
threshold by 1.5% before the comparator becomes inactive,
indicating that the OV condition has gone away (see Figure 6).
V1MON_OV
V1MON
HYSTERESIS
V1MON_UV
HYSTERESIS
OV
OV
COMPARATOR COMPARATOR
ACTIVE
INACTIVE
UV
UV
COMPARATOR COMPARATOR
ACTIVE
INACTIVE
Figure 6. V1MON Hysteresis
When the V1MON input drops below the programmed under-
voltage (UV) threshold, the comparator becomes active
immediately, indicating that a UV condition has occurred.
Similarly, due to hysteresis, the V1MON input must be brought
above the programmed UV threshold by 1.5% before the
comparator becomes inactive, indicating that the UV condition
has gone away.
Both V1MON comparators are used (in conjunction with hold and
delay timers) to control the SHDN and RESET pins.
V1MON has a 16-level programmable OV threshold (Register 0x01)
and UV threshold (Register 0x02) with an 8-step 0.07 ms to
200 ms shutdown hold time (t1SD_HOLD) and 0.07 ms to 1200 ms
AD5100
shutdown delay (t1SD_DELAY). The shutdown hold time means that
the SHDN signal is held low for t1SD_HOLD after V1MON returns
within its UV and OV thresholds. The shutdown delay means
that the SHDN signal activation is delayed until the programmed
t1SD_DELAY has elapsed. SHDN activates once the voltage on V1MON
is outside the OV or UV threshold for a time longer than tGLITCH.
RESET follows SHDN delay and hold timings when triggered
by VIMON.
The OV threshold chosen must be greater than the UV threshold.
When the shutdown is triggered, either because the input has
reached the OV or UV threshold, such fault conditions are
temporarily recorded in the fault detection register.
The SHDNWARN output transitions low for signaling before
the shutdown output, SHDN, activates. The timing of the SHDN
output is dependent on how long the shutdown-programmed
delay (t1SD_DELAY ) is set relative to the SHDNWARN propagation
delay (tFD_DELAY). This feature attempts to allow the system to
finish any critical housekeeping tasks before shutting down the
external device.
The V1MON, shutdown, and shutdown warning timing diagrams
are shown in Figure 7.
The ranges of OV and UV thresholds are shown in Table 6, and
the programming codes for the selected thresholds are found in
Table 7. The defaulted OV threshold is 18.00 V and, for UV
threshold, it is 8.43 V. Similarly, the ranges of shutdown hold
and delay times are shown in Table 8, and the programming
codes for the selected timings are shown in Table 9.
V1MON exhibits typical input resistance of 55 kΩ that users
should take into account for loading effect.
The voltage at V1MON provides the power for the AD5100, but
a valid signal on V2MON must be present before the internal
power rail, VREG, starts operation. Details are explained in the
Power Requirements section.
Rev. A | Page 13 of 36
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