ADT7301 Analog Devices, ADT7301 Datasheet - Page 9

• Manufacturer Part Number: ADT7301
• Description: 13-Bit/ 0.5C Accurate/ MicroPower Digital Temperature Sensor in 6-Lead SOT-23
• Manufacturer: Analog Devices

Preliminary Technical Data
SERIAL INTERFACE
The serial interface on the ADT7301 consists of four wires: CS,
SCLK, DIN, and DOUT. The interface can be operated in 2-
wire mode with CS and DIN tied to ground, in which case the
interface has read-only capability, with data being read from the
data register via the DOUT line. It is advisable to utilize CS,
which improves synchronization between the ADT7301 and the
master device. The DIN line is used to write the part into
standby mode, if required. The CS line is used to select the
device when more than one device is connected to the serial
clock and data lines. The part operates in a slave mode and
requires an externally applied serial clock to the SCLK input to
access data from the data register. The serial interface on the
ADT7301 allows the part to be interfaced to systems that
provide a serial clock synchronized to the serial data, such as
the 80C51, 87C51, 68HC11, 68HC05 and PIC16Cxx
microcontrollers as well as DSP processors.
A read operation from the ADT7301 accesses data from the
temperature value register while a write operation to the part
writes data to the control register.
Read Operation
Figure 13 shows the timing diagram for a serial read from the
ADT7301. The CS line enables the SCLK input. Thirteen bits of
data plus a sign bit are transferred during a read operation.
Read operations occur during streams of 16 clock pulses. The
DOUT
SCLK
DIN
CS
t
1
1
LEADING ZEROS
2
t
2
t
3
3
t
5
POWER-
DB13
DOWN
Figure 13. Serial Interface Timing Diagram
t
6
t
4
4
DB12
Rev. PrJ | Page 9 of 14
first two bits out are leading zeros and the next 14 bits contain
the temperature data. If CS remains low and 16 more SCLK
cycles are applied, the ADT7301 loops around and outputs the
two leading zeros plus the 14 bits of data that are in the temper-
ature value register. When CS returns high, the DOUT line goes
into three-state. Data is clocked out onto the DOUT line on the
falling edge of SCLK.
Write Operation
Figure 13 also shows the timing diagram for a serial write to the
ADT7301. The write operation takes place at the same time as
the read operation. Only the third bit in the data stream
provides a user-controlled function. This third bit is the power-
down bit, which, when set to a 1, puts the ADT7301 into
shutdown mode. Besides the power-down bit, all bits in the
input data stream should be zero to ensure correct operation of
the ADT7301. Data is loaded into the control register on the
16
the part is programmed to go into shutdown, it does so at this
point. If CS is brought high before this 16
control register is not loaded and the power-down status of the
part does not change. Data is clocked into the ADT7301 on the
rising edge of SCLK.
th
DB0
rising SCLK edge; the data takes effect at this time, i.e., if
15
DB1
16
t
7
DB0
t
8
th
SCLK edge, the
ADT7301