ADT7317ARQZ-REEL71 查看數據表（PDF） - Analog Devices

零件编号

产品描述 (功能)

生产厂家

ADT7317ARQZ-REEL71

±0.5°C Accurate Digital Temperature Sensor and Quad Voltage Output 12-/10-/8-Bit DACs

Analog Devices 

THEORY OF OPERATION

Directly after the power-up calibration routine, the ADT7316/

ADT7317/ADT7318 go into idle mode. In this mode, the device

is not performing any measurements and is fully powered up.

All four DAC outputs are at 0 V.

To begin monitoring, write to the Control Configuration 1

register (Address 0x18), and set Bit C0 = 1. The ADT7316/

ADT7317/ADT7318 go into their power-up default measure-

ment mode, which is round robin. The device proceeds to take

measurements on the VDD channel, the internal temperature

sensor channel, and the external temperature sensor channel.

Once it finishes taking measurements on the external tempera-

ture sensor channel, the device immediately loops back to start

taking measurements on the VDD channel and repeats the same

cycle as before. This loop continues until the monitoring is

stopped by resetting Bit C0 of the Control Configuration 1

register to 0.

It is also possible to continue monitoring as well as switching to

single-channel mode by writing to the Control Configuration 2

register (Address 0x19) and setting Bit C4 = 1. Further explana-

tion of the single-channel and round robin measurement modes

is given in later sections. All measurement channels have averaging

enabled on power-up. Averaging forces the device to take an

average of 16 readings before giving a final measured result. To

disable averaging and consequently decrease the conversion

time by a factor of 16, set C5 = 1 in the Control Configuration

2 register.

Controlling the DAC outputs can be done by writing to the DAC

MSB and LSB registers (Address 0x10 to Address 0x17). The

power-up default setting is to have a low going pulse on the

LDAC pin controlling the updating of the DAC outputs from

the DAC registers. Alternatively, users can configure the updating

of the DAC outputs to be controlled by means other than the

LDAC pin by setting C3 = 1 of the Control Configuration 3

register (Address 0x1A). The DAC Configuration register

(Address 0x1B), and the LDAC Configuration register (Address

0x1C) can then be used to control the DAC updating. These

two registers also control the output range of the DACs, enabling

or disabling the external reference buffer, and selecting between

the internal or external reference. DAC A and DAC B outputs

can be configured to give a voltage output proportional to the

temperature of the internal and external temperature sensors,

respectively.

The dual serial interface defaults to the I2C protocol on power-

up. To select and lock in the SPI protocol, follow the selection

process as described in the Serial Interface Selection section.

The I2C protocol cannot be locked in, while the SPI protocol,

when selected, is automatically locked in. The interface can

ADT7316/ADT7317/ADT7318

only be switched back to be I2C when the device is powered

off and on. When using I2C, the CS pin should be tied to either

VDD or GND.

There are a number of different operating modes on the

ADT7316/ADT7317/ADT7318 devices, and all of them can

be controlled by the configuration registers. These features

consist of enabling and disabling interrupts, polarity of the

INT/INT pin, enabling and disabling the averaging on the

measurement channels, SMBus timeout, and software reset.

POWER-UP CALIBRATION

It is recommended that no communication to the part is initiated

until approximately 5 ms after VDD has settled to within 10% of

its final value. It is generally accepted that most systems take a

maximum of 50 ms to power-up. Power-up time is directly

related to the amount of decoupling on the voltage supply line.

During the 5 ms after VDD has settled, the part performs a cali-

bration routine; any communication to the device interrupts

this routine and can cause erroneous temperature measurements.

If it is not possible to have VDD at its nominal value by the time

50 ms has elapsed, or that communication to the device has

started prior to VDD settling, then it is recommended that a

measurement be taken on the VDD channel before a tempera

ture measurement is taken. The VDD measurement is used to

calibrate out any temperature measurement error due to

different supply voltage values.

CONVERSION SPEED

The internal oscillator circuit used by the ADC has the capa-

bility to output two different clock frequencies. This means

that the ADC is capable of running at two different speeds

when performing a conversion on a measurement channel.

Thus, the time taken to perform a conversion on a channel

can be reduced by setting C0 of Control Configuration 3

register (Address 0x1A). This increases the ADC clock speed

from 1.4 kHz to 22 kHz. At the higher clock speed, the analog

filters on the D+ and D− input pins (external temperature

sensor) are switched off. This is why the power-up default

setting is to have the ADC working at the slow speed. The

typical times for fast and slow ADC speeds are given in the

Specifications section.

The ADT7316/ADT7317/ADT7318 power up with averaging

on. This means every channel is measured 16 times and inter-

nally averaged to reduce noise. The conversion time can also

be sped up by turning the averaging off; to do so, set Bit C5 of

the Control Configuration 2 register (Address 0x19) to 1.

Rev. B | Page 19 of 44

Share Link: