LTC2966
8
2966fb
For more information www.linear.com/LTC2966
The LTC2966 is a micropower dual channel voltage monitor
with a 100V maximum operating voltage. Each channel is
comprised of an internal high value resistive divider and a
comparator with a high voltage output. A reference voltage
is provided to allow the thresholds of each channel to be
set independently. This configuration has the advantage
of being able to monitor very high voltages with very little
current draw while threshold configuration is done using
low value resistors at low voltages.
The two channels of the LTC2966 provide independent
monitoring capabilities for multiple voltages or work in
conjunction to set up an undervoltage/overvoltage monitor.
Integration of a resistive divider for high voltage sensing
makes the LTC2966 a compact and low power solution for
generating voltage status signals to a monitoring system.
A built-in buffered reference gives the monitor flexibility to
operate independently from a high voltage supply without
the requirement of additional low voltage biasing. The refer
-
ence provides an accurate voltage from which a resistive
divider to ground configures the threshold voltage for the
internal comparators. In addition, the REF pin can be used
as a logic high voltage for the range and polarity select pins.
The input voltage threshold at V
IN
is determined by the
voltage on the INH and INL pins which are scaled by the
attenuation internal resistive divider. In the LTC2966 the
attenuation of the internal divider is configured using two
range select pins, RS1 and RS2 to select 5x, 10x, 20x or
40x for each channel. Use Table1 to determine the correct
configuration for a desired range setting. The polarity select
pins, (PSA/PSB), configure the corresponding OUT pin to
be inverting or noninverting with respect to V
IN
allowing
the part to be configured for monitoring overvoltage and
undervoltage conditions with either polarity output.
Table 1.
V
IN
MONITOR
RANGE
RANGE
SELECTION
RS1 RS2
1.75V* to 12.25V 5x L L
3.5V to 24.5V 10x H L
7V to 49V 20x L H
14V to 98V 40x H H
*Requires either V
INA
or V
INB
> 3.5V.
The INH pin determines the high or rising edge threshold
for V
IN
in each channel. If the monitored voltage connected
to V
INA
rises to the scaled INHA voltage then the OUT pin
is pulled high assuming PSA is ground. Likewise, the INL
pin determines the low or falling edge threshold for V
IN
in
each channel. If V
INA
falls to the scaled INLA voltage then
the OUT pin is pulled low assuming PSA is ground. The
amount of hysteresis referred to V
IN
is the difference in
voltage between INH and INL scaled according to the RS
pin configuration. INH and INL have an allowable voltage
range, V
CM
. Figure 1 shows the allowable monitor voltage
at V
IN
for each range as a function of comparator reference
input voltage (INL, INH).
Typically, an external resistive divider biased from REF is
used to generate the INH and INL pin voltages. A built-in
hysteresis feature requiring only two resistors can be
enabled on either the V
IN
rising edge by grounding INH
or on the falling edge by grounding INL. For example, it
is appropriate to ground INH to activate rising edge hys
-
teresis if an accurate falling voltage threshold is required
for undervoltage detection. Conversely, it is appropriate
to ground INL for falling edge built-in hysteresis if an ac
-
curate overvoltage threshold is required. Do not ground
both INH and INL. Oscillation occurs if V
INL
> V
INH
unless
INH built-in hysteresis is enabled.
OPERATION
