1

24

READ TS COMMAND

CSB

SCLK

DRDYB

arb.

DIN

8

arbitrary activity

arb.

arbitrary activity

1

12

TDATA

DOUT

24

arb.

LMP92018

SNAS514B – NOVEMBER 2011 – REVISED MAY 2013

www.ti.com

Table 1. Temperature Readout Examples

Temperature

TDATA

125°C

0111.1101.0000

25°C

0001.1001.0000

0.0625°C

0000.0000.0001

0°C

0000.0000.0000

−0.0625°C

1111.1111.1111

−40°C

1101.1000.0000

In Continuous mode, the temperature sensor operates in the background and independently of the SPI bus

activity. Subsequent temperature conversion results are stored in the output register which can be accessed by

the user via the SPI interface.

In One-Shot mode temperature sensor is inactive until the user issues an instruction, via SPI interface, to read

the temperature sensor data. The temperature conversion commences at the rising edge of CSB following the

register. If configured, the DRDYB output indicates when the temperature conversion has been completed, see

Figure 20.

The SPI instruction for accessing the temperature data is described in TEMPERATURE SENSOR OUTPUT

REGISTER

In Figure 20 below a One-Shot temperature read transaction is shown. The temperature readback occupies 2

SPI frames: the first frame is used to issue temperature sensor read instruction, the second frame is used for the

data readback. The falling edge of the DRDYB signal indicates the instance the new temperature data is present

in the output register. The DRDYB is deasserted by the rising edge of the CSB.

NOTE: The DRDYB output in One-Shot temperature conversion mode is asynchronous to the SCLK of

the SPI interface. DRDYB functionality is not provided in the Continuous mode of the temperature sensor

operation.

Figure 20. One-Shot Temperature Read Sequence

INTERNAL VOLTAGE REFERENCE SOURCE

The device has a built in precision 2.5V reference block which can be used to provide reference potential to

either the ADC (AREF) or the DACs (DREF), both at once, or to external load via REF pin. The precision

reference is always isolated from its loads by individual buffers, see Figure 21.

The CREF register sets the reference block mode of operation. The SPI instruction to update or read contents of

the CREF register is shown in REFERENCE CONFIGURE. The switch activity due to the CREF content is

tabulated in Table 2.

The modes corresponding to CREF=(100) or (110) or (111) are the Deep Sleep modes. In these modes the

internal temperature sensor, the ADC, the DACs, and the reference block buffers (but not the 2.5V reference) are

powered down.

22

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