ADM6710
Preliminary Technical Data
THEORY OF OPERATION
V
INTH
The ADM6710 is a compact, low power supervisory circuit
capable of monitoring up to four voltages in multivoltage
applications. If a monitored power supply voltage falls below the
minimum voltage threshold, a single active low output asserts,
triggering a system reset.
R1
R2
V
= 0.62V
REF
The ADM6710 includes several voltage threshold options for
monitoring 5.0 V, 3.3 V, 3.0 V, 2.5 V and 1.8 V supplies. It also
provides up to three adjustable thresholds for monitoring
voltages down to 0.62 V. See the Ordering Guide section for a
list and description of all options available.
Figure 4. Setting the Adjustable Monitor
The ADM6710Q contains an internal voltage clamp at each of
the adjustable voltage inputs. Input voltages greater than 1.5 V
induce a higher input current.
The ADM6710 includes precision comparators, an accurate
band gap reference, and a series of internally-trimmed resistor
divider networks to set the factory-fixed reset threshold
options. The resistor networks scale the specified INx reset
voltages to match the internal band gap reference/comparator
voltage.
The ADM6710 is normally powered from the monitored IN2, or
VCC in the case of the ADM6710Q. Monitored inputs are
resistant to short power supply glitches. To increase noise
immunity in noisy applications, place a 0.1 μF capacitor
between the IN2 input and ground. Adding capacitance to IN1,
IN3, and IN4 also improves noise immunity.
Adjustable threshold options bypass the internal resistor
networks and connect directly to one of the comparator inputs.
External resistor divider networks must be used to scale
voltages down for monitoring at the adjustable inputs. The
ADM6710Q provides a separate unmonitored power supply
input (VCC) and three adjustable voltage inputs.
Do not allow unused monitor inputs to float or to be grounded.
Connect these inputs to a supply voltage greater than their
specified threshold voltages. In the case of unused INx
adjustable inputs, limit the bias current by connecting a 1 MΩ
series resistor between the unused input and IN2 (or VCC with
the ADM6710Q).
The internal comparators each typically have a hysteresis of
0.3% with respect to its reset threshold. This built-in hysteresis
improves the device’s immunity to ambient noise without
noticeably reducing the threshold accuracy. The ADM6710 is
unaffected by short input transients.
RESET OUTPUT CONFIGURATION
The ADM6710 has a reset timeout period of 200 ms (typical).
The output is open drain with a weak internal pull-up to the
monitored IN2 or VCC supply, typically 10 uA.
In many applications that interface with other logic devices,
there is no requirement for an external pull-up resistor. An
external pull-up resistor to any voltage, ranging from 0 V to
5.5 V, can overdrive the internal pull-up when interfacing to
different logic supply voltages (see Figure 5). Reverse current
flow from the external pull-up voltage to IN2 is prevented by
the internal circuitry.
ADM6710
IN
IN
IN
IN
1
2
3
4
MONITORED
SUPPLIES
MICROPROCESSOR
RESET
GND
Figure 3. Typical Applications Circuit
IN =3.3V
2
5V
INPUT CONFIGURATION
V
CC
The ADM6710 provides numerous monitor choices with
adjustable reset thresholds. Typically, the threshold voltage at
each adjustable INx input is 0.62 V. To monitor a voltage greater
than 0.62 V, connect a resistor divider network to the circuit as
depicted in Figure 4, where
100kΩ
ADM6710
RESET
RESET
⎛
⎜
⎜
⎝
⎞
⎟
⎟
⎠
R1 + R2
R2
VINTH = 0.62 V
Figure 5. Interface with a Different Logic Supply Voltage
The ADM6710Q is powered by VCC, which is not a monitored
voltage. All other ADM6710 options are powered by IN2, which
is a monitored voltage. If a supply voltage drops below its
associated threshold, the reset output asserts low and remains
low while either IN1 or IN2 remains above 1.0 V.
Rev. PrB | Page 6 of 8