ADM1266ACPZ-R7 datasheet(15/62 Pages) AD

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Data Sheet

ADM1266

Rev. A | Page 15 of 62

INPUTS

Supply Fault Detectors

The ADM1266 has 17 programmable supply fault detector (SFD)

inputs. These dedicated inputs are labeled VHx (VH1 to VH4)

and VPx (VP1 to VP13). The ADM1266 is also capable of making

precision differential voltage measurements on the VPx pins

(the exception is that VP13 cannot be used for differential

measurements). One differential measurement requires two

VPx pins. The odd numbered VPx pin (for example, VP1) must

always be the greater voltage. The next corresponding even number

VPx pin (for example, VP2) is used for that differential measure-

ment. Both differential VPx pins must have the same input

range selections. The SFD for the odd numbered VPx pin

responds to the differential measurement. Figure 9 shows the

arrangement of the pins. Each SFD input can be configured to

detect an undervoltage (UV) fault (the input voltage drops below a

preprogrammed value), or an overvoltage (OV) fault (the input

voltage rises above a preprogrammed value). A programmable

(up to 100 μs) glitch filter allows the user to remove any

spurious transitions such as supply bounce at turn on.

RANGE

SELECT

–

OUT

GLITCH

FILTER

VHx

OUT

GLITCH

FILTER

SETTINGS

RANGE

SELECT

–

OUT

GLITCH

FILTER

VPx

(ODD)

OUT

GLITCH

FILTER

SETTINGS

RANGE

SELECT

–

OUT

GLITCH

FILTER

VPx

(EVEN)

OUT

GLITCH

FILTER

SETTINGS

DIFFERENTIAL

SELECTION

VHx ADC INPUT

VPx ADC INPUT

HIGH-Z

–

VPx ADC INPUT

DAC

Figure 9. Supply Fault Detectors

The voltage range limits for threshold settings are

•

0.4 V to 1.0 V

•

0.75 V to 1.875 V

•

1.5 V to 3.75 V

•

2.0 V to 5.0 V (VPx pins only)

•

3.0 V to 7.5 V (VHx pins only)

•

6.0 V to 15.0 V (VHx pins only)

When connecting directly to the voltage source, a 100 Ω resistor

in series is recommended to avoid any latch-ups on the VHx and

VPx pins. VH1 and VH2 are supply pins and do not need the

100 Ω resistor in series.

Input Comparator Hysteresis

The UV and OV comparators shown in Figure 9 are always

monitoring and sensing the voltage on VHx and 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 is added after a supply voltage goes out

of tolerance. Therefore, the user can program the amount above

the UV threshold to which the input must rise before a UV fault

is deasserted. Similarly, the user can program the amount below the

OV threshold to which an input must fall before an OV fault is

deasserted.

Glitch Filter

The ADM1266 has a dedicated digital glitch filter at the output of

each comparator. For the fault to trigger, the comparator must

remain set for the time greater than the programmed glitch filter

time. This time can be programmed from 2 μs to 100 μs and is used

for filtering any transient noises that may occur on the VHx and

VPx pins.

Using External Resistor Dividers

External resistor dividers can be used to sense higher voltages or to

achieve higher accuracy. When using an external resistor divider,

select the 0.4 V to 1 V high impedance range on the VPx pins. It is

recommended that the resistor divider be sized such that, under

nominal conditions, there is 0.7 V at the VPx pins to provide the

highest range for the OV and UV settings.

The size of the external resistor divider can be input into the device

using the VOUT_SCALE_MONITOR command (Register 0x2A).

Warnings

The UV and OV warnings are generated by comparing the

VOUT_OV_WARN_LIMIT (Register 0x42) and (Register 0x43)

VOUT_UV_WARN_LIMIT with the reading from the ADC.

Because the ADC round robin time is 5 ms, the maximum delay

from the warning occurring to the device detecting it is 5 ms.

Warnings are not sent to the sequence engine and cannot be used

to trigger events in the state machine. Instead, the warnings are sent

to the logic block and can be used to assert/deassert PDIOs and

GPIOs.

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