AD7280 datasheet(22/33 Pages) AD

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AD7280

Preliminary Technical Data

Rev. PrD | Page 22 of 33

Read Conversion Results

Bits D13 and D12 of the CONTROL register determine which

cell voltages and temperatures conversion results are supplied to

the serial or Daisychain data outputs pins for readback. The

default value of D15 and D14 on power up are 00.

Conversion Start Format

The AD7280 offers two methods of initiating a conversion, the

hardware CNVST pin or the software CS input. Bit D11 of the

CONTROL register determines whether a conversion is

initiated on the falling edge of the CNVST input or on the rising

edge of the CS input. The default format on power up is the

CNVST pin.

Conversion Averaging

Bits D10 and D9 of the CONTROL register determines the

number of conversions completed on each input with the

average result being stored in the Result registers. The default

value of the Conversion Averaging bits is 00, that is no

averaging.

Powerdown Format

Bit D8 of the CONTROL register allows the AD7280 be placed

into a software powerdown. Pleas refer to the Power Down

section of more details. The default format on power up is the

PD pin.

Software Reset

Bit D7 of the CONTROL register allows the user to initiate a

software Reset of the AD7280. Two write commands are

required to complete the reset operation. Bit D7 must be set

high to put the AD7280 into Reset. Bit D7 must then be set low

to bring the AD7280 out of Reset.

Select Acquisition Time

Bits D6 and D5 of the CONTROL register determine the

Acquisition time of the ADC. Please refer to the Track-and-

Hold section for further detail. The default value of the

Conversion time setting is 00.

Table 15.Analog Input Acquisition Time.

D6 to D5

Acquisition Time

400 ns

800 ns

1.2

µs

1.6

µs

Thermistor Termination Resistor

Bit D3 of the CONTROL register should be set if the user

wishes to use a single thermistor termination resistor on the

VTTERM pin. It should be noted that, due to settling time

requirements, the thermistor termination resistor option should

only be used when the acquisition time of the AD7280 is set to

its highest value, that is 1.6µs.

OVER VOLTAGE REGISTER

Table 16. 8-Bit Register

D7 to D0

Read/Write

The OVERVOLTAGE THRESHOLD register determines the

high voltage threshold of the AD7280. Cell voltage conversions

which exceed the Over Voltage threshold trigger the ALERT

output. The AD7280 allows the user to set the Over Voltage

threshold to a value between 1V and 5V. The resolution of the

Over Voltage threshold is 8-bits, that is 16mV. The default value

of the Over Voltage threshold on power up is TBD mV.

UNDER VOLTAGE REGISTER

Table 17. 8-Bit Register

10h

D7 to D0

Read/Write

The UNDER VOLTAGE THRESHOLD register determines the

low voltage threshold of the AD7280. Cell voltage conversions

lower than the Under Voltage threshold trigger the ALERT

output. The AD7280 allows the user to set the Under Voltage

threshold to a value between 1V and 5V. The resolution of the

Under Voltage threshold is 8-bits, that is 16mV. The default

value of the Under Voltage threshold on power up is TBD mV.

OVER TEMP REGISTER

Table 18. 8-Bit Register

11h

D7 to D0

Read/Write

The OVER TEMP THRESHOLD register determines the high

temperature threshold of the AD7280. Cell temperature

conversions which exceed the Over Temp threshold trigger the

ALERT output. The AD7280 allows the user to set the Over

Temperature threshold to a value between 0V and 5V. The

resolution of the Over Temperature threshold is 8-bits, that is

19mV. The default value of the Over Voltage threshold on

power up is TBD mV.

UNDER TEMP REGISTER

Table 19. 8-Bit Register

12h

D7 to D0

Read/Write

The UNDER TEMP THRESHOLD register determines the low

temperature threshold of the AD7280. Cell temperature

conversions lower than the Under Voltage threshold trigger the

ALERT output. The AD7280 allows the user to set the Under

Temperature threshold to a value between 0V and 5V. The

resolution of the Under Voltage threshold is 8-bits, that is 19mV.

The default value of the Under Voltage threshold on power up is

TBD mV.

ALERT REGISTER

Table 20. 8-Bit Register

13h

D7 to D0

Read/Write

The ALERT register determines the configuration of the ALERT

function. The ALERT can be configured to be a static signal or

a square wave. The static signal can be programmed to be

either high or low. The frequency of the square wave can be set

to either 100Hz or 1kHz. When a number of AD7280s are

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