AD7853 Analog Devices, AD7853 Datasheet - Page 24

• Manufacturer Part Number: AD7853
• Description: 3 V to 5 V Single Supply, 200 kSPS, 12-Bit, Serial Sampling ADC
• Manufacturer: Analog Devices

Specifications of AD7853

• Resolution (bits): 12bit
• # Chan: 1
• Sample Rate: 200kSPS
• Interface: Ser,SPI
• Analog Input Type: Diff-Uni,SE-Uni
• Ain Range: (Vref) p-p,Uni (Vref)
• Adc Architecture: SAR
• Pkg Type: DIP,SOIC

AD7853/AD7853L
DETAILED TIMING SECTION
Mode 1 (2-Wire 8051 Interface)
The read and writing takes place on the DIN line and the con-
version is initiated by pulsing the CONVST pin (note that in
every write cycle the 2/3 Mode bit must be set to 1). The con-
version may be started by setting the CONVST bit in the con-
trol register to 1 instead of using the CONVST line.
Below in Figure 33 and in Figure 34 are the timing diagrams for
Interface Mode 1 in Table X where we are in the 2-wire inter-
face mode. Here the DIN pin is used for both input and output
as shown. The SYNC input is level triggered active low and can
be pulsed (Figure 33) or can be constantly low (Figure 34).
In Figure 33 the part samples the input data on the rising edge
of SCLK. After the 16th rising edge of SCLK the DIN is con-
figured as an output. When the SYNC is taken high the DIN is
three-stated. Taking SYNC low disables the three-state on the
DIN pin and the first SCLK falling edge clocks out the first data
bit. Once the 16 clocks have been provided the DIN pin will
automatically revert back to an input after a time t
continuous SCLK shown by the dotted waveform in Figure 33
Figure 33. Timing Diagram for Read/Write Operation with DIN as an Input/Output (i.e., Interface Mode 1, SM1 = SM2 = 0)
Figure 34. Timing Diagram for Read/Write Operation with DIN as an Input/Output and SYNC Input Tied Low
(i.e., Interface Mode 1, SM1 = SM2 = 0)
SYNC (I/P)
SCLK (I/P)
SCLK (I/P)
DIN (I/O)
DIN (I/O)
POLARITY PIN
LOGIC HIGH
POLARITY PIN
LOGIC HIGH
t
3
DB15
t
DB15
7
t
t
t
7
3
6
1
1
= –0.4 t
= 75/115 MAX (5V/3V), t
t
t
6
13
t
8
= 75/115 MAX (5V/3V), t
t
8
= 90/130 MAX (5V/3V), t
DATA WRITE
DATA WRITE
SCLK
MIN (NONCONTINUOUS SCLK) –/+0.4 t
14
. Note that a
DIN BECOMES AN OUTPUT
DB0
DB0
16
16
7
= 40/60ns MIN (5V/3V), t
7
t
14
11
= 40/60ns MIN (5V/3V), t
= 50/90ns MAX (5V/3V)
t
12
–24–
t
THREE-STATE
13
can be used provided that the SYNC is low for only 16 clock
pulses in each of the read and write cycles. The POLARITY pin
may be used to change the SCLK edge which the data is sampled
on and clocked out on.
In Figure 34 the SYNC line is tied low permanently and this
results in a different timing arrangement. With SYNC tied low
permanently the DIN pin will never be three-stated. The 16th
rising edge of SCLK configures the DIN pin as an input or an
output as shown in the diagram. Here no more than 16 SCLK
pulses must occur for each of the read and write operations.
If reading from and writing to the calibration registers in this
interface mode, all the selected calibration registers must be
read from or written to. The read and write operations cannot
be aborted. When reading from the calibration registers, the
DIN pin will remain as an output for the full duration of all the
calibration register read operations. When writing to the calibra-
tion registers, the DIN pin will remain as an input for the full
duration of all the calibration register write operations.
t
3
8
= 20/30 MIN (5V/3V)
8
SCLK
= 20/30 MIN (5V/3V),
1
t
1
5A
DB15
DB15
MIN/MAX (CONTINUOUS SCLK),
t
6
t
6
DATA READ
DATA READ
6
t
6
t
6
16
16
DB0
DIN BECOMES AN INPUT
DIN BECOMES AN INPUT
DB0
t
11
t
t
14
14
REV. B