ADM1168 データシートの表示（PDF） - Analog Devices

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ADM1168

Super Sequencer and Monitor with Nonvolatile Fault Recording

Analog Devices 

Data Sheet

INPUTS

SUPPLY SUPERVISION

The ADM1168 has eight programmable inputs. Four of these

are dedicated supply fault detectors (SFDs). These dedicated

inputs are called VH and VPx (VP1 to VP3) by default. The

other four inputs are labeled VXx (VX1 to VX4) and have dual

functionality. They can be used either as SFDs, with functionality

similar to the VH and VPx, or as CMOS-/TTL-compatible logic

inputs to the device. Therefore, the ADM1168 can have up to

eight analog inputs, a minimum of four analog inputs and four

digital inputs, or a combination thereof. If an input is used as

an analog input, it cannot be used as a digital input. Therefore, a

configuration requiring eight analog inputs has no available

digital inputs. Table 6 shows the details of each input.

PROGRAMMING THE SUPPLY FAULT DETECTORS

The ADM1168 can have up to eight SFDs on its eight input

channels. These highly programmable reset generators enable

the supervision of up to eight supply voltages. The supplies can

be as low as 0.573 V and as high as 14.4 V. The inputs can be

configured to detect an undervoltage fault (the input voltage

drops below a preprogrammed value), an overvoltage fault (the

input voltage rises above a preprogrammed value), or an out-of-

window fault (the input voltage is outside a preprogrammed

range). The thresholds can be programmed to an 8-bit resolution

in registers provided in the ADM1168. This translates to a

voltage resolution that is dependent on the range selected.

The resolution is given by

Step Size = Threshold Range/255

Therefore, if the high range is selected on VH, the step size can

be calculated as follows:

(14.4 V − 6.0 V)/255 = 32.9 mV

ADM1168

Table 5 lists the upper and lower limits of each available range,

the bottom of each range (VB), and the range itself (VR).

Table 5. Voltage Range Limits

Voltage Range (V)

0.573 to 1.375

1.25 to 3.00

2.5 to 6.0

6.0 to 14.4

VB (V)

0.573

1.25

2.5

6.0

VR (V)

0.802

1.75

3.5

8.4

The threshold value required is given by

VT = (VR × N)/255 + VB

where:

VT is the desired threshold voltage (undervoltage or overvoltage).

VR is the voltage range.

N is the decimal value of the 8-bit code.

VB is the bottom of the range.

Reversing the equation, the code for a desired threshold is given by

N = 255 × (VT − VB)/VR

For example, if the user wants to set a 5 V overvoltage threshold

on VP1, the code to be programmed in the PS1OVTH register

(as described in the AN-721 Application Note) is given by

N = 255 × (5 − 2.5)/3.5

Therefore, N = 182 (1011 0110 or 0xB6).

Rev. B | Page 11 of 27

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