AD7478A Analog Devices, AD7478A Datasheet - Page 9

• Manufacturer Part Number: AD7478A
• Description: 8-Bit, 1 MSPS, Low-Power A/D Converter in SC70 and MSOP Packages
• Manufacturer: Analog Devices

Specifications of AD7478A

• Resolution (bits): 8bit
• # Chan: 1
• Sample Rate: 1.2MSPS
• Interface: Ser,SPI
• Analog Input Type: SE-Uni
• Ain Range: Uni Vdd
• Adc Architecture: SAR
• Pkg Type: SC70,SOP

Timing Diagrams
Timing Example 1
Having f
time of
where:
t
requirement of 250 ns for t
From Figure 4, t
where:
t
satisfying the minimum requirement of 50 ns.
2
8
= 36 ns maximum. This allows a value of 204 ns for t
= 10 ns min, leaving t
t
2.5 (1/f
2
Figure 2. Load Circuit for Digital Output Timing Specifications
+ 12.5 (1/f
SDATA
SCLK
SCLK
SCLK
CS
CS
TO OUTPUT
SCLK
= 20 MHz and a throughput of 1 MSPS, a cycle
THREE-
) + t
STATE
ACQ
SCLK
PIN
is comprised of
8
) + t
+ t
t
t
2
50pF
2
Z
ACQ
QUIET
C
1
1
ACQ
t
L
3
ZERO
ACQ
to be 365 ns. This 365 ns satisfies the
4 LEADING ZEROS
= 1 µs
200 µ A
200 µ A
.
2
2
ZERO
I
I
OL
OH
3
3
ZERO
t
4
12.5(1/f
1.6V
4
Figure 3. AD7476A Serial Interface Timing Diagram
4
SCLK
DB11
t
Figure 4. Serial Interface Timing Example
t
6
)
CONVERT
QUIET
5
t
5
CONVERT
t
DB10
7
,
Rev. F | Page 9 of 28
1/THROUGHPUT
13
13
B
B
DB2
Timing Example 2
Having f
cycle time of
where:
t
the requirement of 250 ns for t
From Figure 4, t
This allows a value of 128 ns for t
requirement of 50 ns.
In this example and with other, slower clock values, the signal
may already be acquired before the conversion is complete, but
it is still necessary to leave 50 ns minimum t
conversions. In Example 2, acquire the signal fully at
approximately Point C in Figure 4.
2
= 10 ns min, this leaves t
14
t
2.5 (1/f
14
t
2
5
+ 12.5 (1/f
DB1
SCLK
C
SCLK
= 5 MHz and a throughput is 315 kSPS yields a
15
15
) + t
ACQ
DB0
SCLK
t
AD7476A/AD7477A/AD7478A
is comprised of
8
ACQ
16
) + t
t
+ t
16
8
QUIET
ACQ
t
8
THREE-STATE
ACQ
, t
= 3.174 µs
8
to be 664 ns. This 664 ns satisfies
ACQ
= 36 ns maximum
t
t
.
QUIET
QUIET
QUIET
t
1
, satisfying the minimum
QUIET
between