_______________Detailed Description

As shown in the block diagram of Figure 2, the Maxim

ICL7665 combines a 1.3V reference with two com-

parators, two open-drain N-channel outputs, and two

open-drain P-channel hysteresis outputs. The refer-

ence and comparator are very low-power linear CMOS

circuits, with a total operating current of 10

µA maxi-

mum, 3

µA typical. The N-channel outputs can sink

greater than 10mA, but are unable to source any cur-

rent. These outputs are suitable for wire-OR connections

and are capable of driving TTL inputs when an external

pull-up resistor is added.

The ICL7665 Truth Table is shown in Table 1. OUT1 is

an inverting output; all other outputs are noninverting.

HYST1 and HYST2 are P-channel current sources

whose sources are connected to V+. OUT1 and OUT2

are N-channel current sinks with their sources connect-

ed to ground. Both OUT1 and OUT2 can drive at least

In spite of the very low operating current, the ICL7665

has a typical propagation delay of only 75

µs. Since the

comparator input bias current and the output leakages

are very low, high-impedance external resistors can be

used. This design feature minimizes both the total sup-

ply current used and loading on the voltage source that

is being monitored.

Microprocessor Voltage Monitor with

Dual Over/Undervoltage Detection

6

_______________________________________________________________________________________

Figure 1. Test Circuit

HYST2 = OFF = LOW

OUT2 = ON = LOW

HYST2 = ON = HI

OUT2 = OFF = HI

HYST1 = OFF = LOW

OUT1 = OFF = HI

HYST1 = ON = HI

OUT1 = ON = LOW

HYSTERESIS

OUTPUT

INPUT*

Table 1. ICL7665 Truth Table

V+

HYST1

HYST2

OUT1

OUT2

TO V+

SET2

SET1

1.3V

BANDGAP

REFERENCE

Figure 2. Block Diagram

1

2

3

4

8

7

6

5

ICL7665

OUT1

HYST1

SET1

GND

V+

OUT2

SET2

HSYT2

12pF

12pF

12pF

12pF

OUT1

HYST1

OUT2

HSYT2

4.7k

4.7k

V+

1.6V

1.0V

INPUT

20k

20k

* See Electrical Characteristics

OUT1 is an inverting output; all others are noninverting. OUT1

and OUT2 are open-drain, N-channel current sinks. HYST1

and HYST2 are open-drain, P-channel current sinks.