_______________________________________________________________________________________ 7

µP Supervisory Circuits in

4-Bump (1mm x 1mm) Chip-Scale Package

Manual Reset Input (MR)

Many FP-based products require manual-reset capabil-

ity, allowing the operator, a test technician, or external

logic circuit to initiate a reset. A logic-low on MR asserts

reset. Reset remains asserted while MR is low, and for

MR returns high. This input has an internal 50kI pullup

resistor, so it can be left unconnected if it is not used.

MR can be driven with TTL or CMOS logic levels, or

with open-drain/collector outputs. For manual operation,

connect a normally open momentary switch from MR to

GND; external debouncing circuitry is not required. If MR

is driven from long cables or if the device is used in a

noisy environment, connect a 0.1FF capacitor from MR to

ground to provide additional noise immunity.

Applications Information

Bidirectional Reset Pins

Since RESET on the MAX16074 is open-drain, this

device interfaces easily with FPs that have bidirectional

reset pins. Connecting the FP supervisor’s RESET output

directly to the FP’s RESET pin with a single pullup resis-

tor allows either device to assert reset (Figure 2).

The MAX16072/MAX16073/MAX16074 family of devic-

es is relatively immune to short-duration, negative-

Characteristics show the Maximum Transient Duration

vs. Reset Threshold Overdrive graph, for which reset

pulses are not generated. The graph shows the maxi-

may typically have when issuing a reset signal. As the

amplitude of the transient increases, the maximum allow-

able pulse width decreases.

Figure 2. Interfacing to

Table 1. Factory Trimmed Reset

Thresholds

Table 2. Reset Timeout Periods

RESET

INPUT

µP

RESET

GND

GND

MR

MAX16074

MOTOROLA

68HCXX

THRESHOLD

SUFFIX

RESET TRIP THRESHOLD (V)

TYP

MIN

MAX

15

1.58

1.54

1.61

16

1.63

1.60

1.66

17

1.67

1.62

1.71

18

1.80

1.76

1.85

19

1.90

1.85

1.95

20

2.00

1.95

2.05

21

2.10

2.05

2.15

22

2.20

2.145

2.25

23

2.32

2.262

2.375

24

2.40

2.34

2.46

25

2.50

2.437

2.562

26

2.63

2.564

2.69

27

2.70

2.633

2.768

28

2.80

2.63

2.87

29

2.93

2.857

3.0

30

3.00

2.925

3.075

31

3.08

3.003

3.15

RESET TIMEOUT PERIODS

SUFFIX

MIN

TYP

MAX

UNITS

0

20

80

120

F

s

1

8

13

17

ms

2

34

52

69

ms

3

140

210

280

ms