ADM1168ASTZ datasheet(12/28 Pages) AD

12 / 28 page

ADM1168

Rev. 0 | Page 12 of 28

INPUT COMPARATOR HYSTERESIS

The UV and OV comparators shown in Figure 16 are always

monitoring VPx. To avoid chatter (multiple transitions when the

input is very close to the set threshold level), these comparators

have digitally programmable hysteresis. The hysteresis can be

programmed up to the values shown in Table 6.

The hysteresis is added after a supply voltage goes out of

tolerance. Therefore, the user can program the amount above

the undervoltage threshold to which the input must rise before

an undervoltage fault is deasserted. Similarly, the user can program

the amount below the overvoltage threshold to which an input

must fall before an overvoltage fault is deasserted.

The hysteresis value is given by

VHYST = VR × NTHRESH/255

where:

VHYST is the desired hysteresis voltage.

NTHRESH is the decimal value of the 5-bit hysteresis code.

Note that NTHRESH has a maximum value of 31. The maximum

hysteresis for the ranges is listed in Table 6.

INPUT GLITCH FILTERING

The final stage of the SFDs is a glitch filter. This block provides

time-domain filtering on the output of the SFD comparators,

which allows the user to remove any spurious transitions such

as supply bounce at turn-on. The glitch filter function is in addition

to the digitally programmable hysteresis of the SFD comparators.

The glitch filter timeout is programmable up to 100 μs.

For example, when the glitch filter timeout is 100 μs, any pulse

appearing on the input of the glitch filter block that is less than

100 μs in duration is prevented from appearing on the output of

the glitch filter block. Any input pulse that is longer than 100 μs

appears on the output of the glitch filter block. The output is

delayed with respect to the input by 100 μs. The filtering process is

shown in Figure 15.

tGF

INPUT

INPUT PULSE SHORTER

THAN GLITCH FILTER TIMEOUT

INPUT PULSE LONGER

THAN GLITCH FILTER TIMEOUT

OUTPUT

PROGRAMMED

TIMEOUT

PROGRAMMED

TIMEOUT

INPUT

OUTPUT

Figure 15. Input Glitch Filter Function

–

COMPARATOR

VREF

FAULT TYPE

SELECT

COMPARATOR

FAULT

OUTPUT

GLITCH

FILTER

VPx

MID

LOW

RANGE

SELECT

ULTRA

LOW

Figure 16. Supply Fault Detector Block

Table 6. Input Functions, Thresholds, and Ranges

Input

Function

Voltage Range (V)

Maximum Hysteresis

Voltage Resolution (mV)

Glitch Filter (μs)

High voltage analog input

2.5 to 6.0

425 mV

13.7

0 to 100

6.0 to 14.4

1.02 V

32.9

0 to 100

VPx

Positive analog input

0.573 to 1.375

97.5 mV

3.14

0 to 100

1.25 to 3.00

212 mV

6.8

0 to 100

2.5 to 6.0

425 mV

13.7

0 to 100

VXx

High-Z analog input

0.573 to 1.375

97.5 mV

3.14

0 to 100

Digital input

0 to 5.0

Not applicable

0 to 100

ADM1168ASTZ Datasheet(PDF) 12 Page - Analog Devices

ADM1168ASTZ Datasheet(HTML) 12 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

Datasheet Download

Link URL