ADM2914

Rev. 0 | Page 8 of 16

THEORY OF OPERATION

VOLTAGE SUPERVISION

The ADM2914 supervises up to four voltage rails for overvol-

tage and undervoltage conditions. Two pins, VHx and VLx, are

assigned to monitor each rail, one for overvoltage detection and

the other for undervoltage detection. Each pin is connected to

the input of an internal voltage comparator, and its voltage level

is internally compared with a 0.5 V voltage reference with

accuracy of ±1.5%.

The output of each of the internal undervoltage comparators is

tied to a common UV output pin. Likewise, the outputs of the

internal overvoltage comparators are tied to a common

VH1

1.8V

VL1

VH2

VL2

VH3

VL3

VH4

VL4

SEL

TIMER

UV

OV

LATCH/DIS

REF

GND

ADM2914

2.5V

3.3V

5V

SYSTEM

PSU

OV

output pin.

Figure 16. Typical Applications Diagram

POLARITY CONFIGURATION

The ADM2914 is capable of monitoring supply voltages of both

positive and negative polarities. The SEL pin is a three-state pin

that determines the polarity of Input 3 and Input 4. As summa-

or left unconnected.

When an input is configured to monitor a positive voltage, using

the three-resistor scheme shown in Figure 17, VHx is connected

to the high-side tap of the resistor divider and VLx is connected

to the low-side tap of the resistor divider.

Conversely, when an input is configured to monitor a negative

voltage, UVx and OVx are swapped internally. The negative

voltage for monitoring is then connected as shown in Figure 18.

VHx is still connected to the high-side tap and VLx is still

connected to the low-side tap. Within this configuration, an

undervoltage condition occurs when the monitored voltage is less

negative than the programmed threshold, and an overvoltage

condition occurs when the monitored voltage is more negative

than the configured threshold.

Table 5. Polarity Configuration

Input 3

Input 4

SEL Pin

Polarity

UV Condition

OV Condition

Polarity

UV Condition

OV Condition

Connected to V

CC

Positive

VH3 < 0.5 V

VL3 > 0.5 V

Positive

VH4 < 0.5 V

VL4 > 0.5 V

Left Unconnected

Positive

VH3 < 0.5 V

VL3 > 0.5 V

Negative

VL4 > 0.5 V

VH4 < 0.5 V

Connected to GND

Negative

VL3 > 0.5 V

VH3 < 0.5 V

Negative

VL4 > 0.5 V

VH4 < 0.5 V