ADM1063ASU datasheet(20/36 Pages) AD

20 / 36 page

ADM1063

Rev. 0 | Page 20 of 36

VOLTAGE READBACK

The ADM1063 has an on-board, 12-bit, accurate ADC for

voltage readback over the SMBus. The ADC has a 12-channel

analog mux on the front end. The 12 channels consist of the

10 SFD inputs (VH, VP1 to VP4, and VX1 to VX5) plus two

channels for temperature readback (discussed in the Remote

Temperature Measurement section). Any or all of these inputs

can be selected to be read, in turn, by the ADC. The circuit

controlling this operation is called the round-robin circuit. The

round-robin circuit can be selected to run through its loop of

conversions once or continuously. Averaging is also provided

for each channel. In this case, the round-robin circuit runs

through its loop of conversions 16 times before returning a

result for each channel. At the end of this cycle, the results are

written to the output registers.

The ADC samples single-sided inputs with respect to the AGND

pin. A 0 V input gives out Code 0, and an input equal to the

voltage on REFIN gives out full code (4095 decimal).

The inputs to the ADC come directly from the VXn pins and

from the back of the input attenuators on the VPn and VH pins,

as shown in Figure 30 and Figure 31.

VXn

2.048V VREF

NO ATTENUATION

12-BIT

ADC

DIGITIZED

VOLTAGE

READING

Figure 30. ADC Reading on VXn Pins

2.048V VREF

ATTENUATION NETWORK

(DEPENDS ON RANGE SELECTED)

12-BIT

ADC

DIGITIZED

VOLTAGE

READING

VPn/VH

Figure 31. ADC Reading on VPn/VH Pins

The voltage at the input pin can be derived from the

following equation:

V =

4095

Code

ADC

× Attenuation Factor × 2.048 V

The ADC input voltage ranges for the SFD input ranges

are listed in Table 8.

Table 8. ADC Input Voltage Ranges

SFD Input

Range (V)

Attenuation Factor

ADC Input Voltage

Range (V)

0.573 to 1.375

0 to 2.048

1.25 to 3

2.181

0 to 4.46

2.5 to 6

4.363

0 to 6.01

4.8 to 14.4

10.472

0 to 14.41

1 The upper limit is the absolute maximum allowed voltage on these pins.

The normal way to supply the reference to the ADC on the

REFIN pin is to simply connect the REFOUT pin to the

REFIN pin. REFOUT provides a 2.048 V reference. As such,

the supervising range covers less than half of the normal ADC

range. It is possible, however, to provide the ADC with a more

accurate external reference for improved readback accuracy.

Supplies can also be connected to the input pins purely for ADC

readback, even though they might go above the expected super-

visory range limits (as long as they are not above 6 V, because

this violates the absolute maximum ratings on these pins). For

instance, a 1.5 V supply connected to the VX1 pin can be correctly

read out as an ADC code of approximately 3/4 full scale, but it

always sits above any supervisory limits that can be set on that

pin. The maximum setting for the REFIN pin is 2.048 V.

SUPPLY SUPERVISION WITH THE ADC

In addition to the readback capability, a further level of supervi-

sion is provided by the on-chip, 12-bit ADC. The ADM1063 has

limit registers on which the user can program a maximum or

minimum allowable threshold. Exceeding the threshold generates

a warning that can either be read back from the status registers

or input into the SE to determine what sequencing action the

ADM1063 should take. Only one register is provided for each

input channel; therefore, either a UV or OV threshold (but not

both) can be set for a given channel. The round-robin circuit

can be enabled via an SMBus write, or it can be programmed to

turn on in any state in the SE program. For example, it can be

set to start once a power-up sequence is complete and all

supplies are known to be within expected tolerance limits.

Note that a latency is built into this supervision, dictated by

the conversion time of the ADC. With all 12 channels selected,

the total time for the round-robin operation (averaging off) is

approximately 6 ms (500 µs per channel selected). Supervision

using the ADC, therefore, does not provide the same real time

response as the SFDs.

ADM1063ASU Datasheet(PDF) 20 Page - Analog Devices

ADM1063ASU Datasheet(HTML) 20 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 29 30 31 32 33 34 35 36

Datasheet Download

Link URL