AD7357BRUZ-RL Analog Devices Inc, AD7357BRUZ-RL Datasheet - Page 17

• Manufacturer Part Number: AD7357BRUZ-RL
• Description: 14-Bit Dual Diff Simult 5 MSPS ADC I.C.
• Manufacturer: Analog Devices Inc

Specifications of AD7357BRUZ-RL

• Design Resources: DC-Coupled, Single-Ended-to-Differential Conversion Using AD8138 and AD7357 (CN0061)
• Number Of Bits: 14
• Sampling Rate (per Second): 4.2M
• Data Interface: DSP, MICROWIRE™, QSPI™, Serial, SPI™
• Number Of Converters: 2
• Power Dissipation (max): 59mW
• Voltage Supply Source: Single Supply
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-TSSOP (0.173", 4.40mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

POWER-UP TIMES
The AD7357 has two power-down modes: partial power-
down and full power-down. There are described in detail in
the Partial Power-Down Mode and Full Power-Down Mode
sections. This section deals with the power-up time required
when coming out of either of these modes. It should be noted
that the power-up times apply with the recommended decoupling
capacitors in place on the REF
To power up from partial power-down mode, one dummy cycle
is required. The device is fully powered up after approximately
200 ns from the falling edge of
power-up time has elapsed, the ADC is fully powered up and
the input signal is acquired properly. The quiet time, t
still be allowed from the point where the bus goes back into three-
state after the dummy conversion to the next falling edge of
To power up from full power-down, approximately 6 ms should
be allowed from the falling edge of
t
Note that during power-up from partial power-down mode, the
track-and-hold, which is in hold mode while the part is powered
down, returns to track mode after the first SCLK edge that the
part receives after the falling edge of
When power supplies are first applied to the AD7357, the ADC
can power up in either of the power-down modes or in normal
mode. Because of this, it is best to allow a dummy cycle to elapse
to ensure that the part is fully powered up before attempting
a valid conversion. Likewise, if the part is to be kept in partial
power-down mode immediately after the supplies are applied,
then two dummy cycles must be initiated. The first dummy
cycle must hold
in the second cycle,
second and 10
POWER-UP2
.
th
CS
SCLK falling edges (see
low until after the 10
CS
must be brought high between the
A
CS
and REF
has elapsed. Once the partial
CS
CS
, shown in
.
Figure 25
th
B
pins.
SCLK falling edge;
Figure 28
).
QUIET
, must
as
CS
Rev. A | Page 17 of 20
.
Alternatively, if the part is to be placed into full power-down
mode when the supplies are applied, three dummy cycles must
be initiated. The first dummy cycle must hold CS low until after
the 10
place the part into full power-down mode (see
the
POWER vs. THROUGHPUT RATE
The power consumption of the AD7357 varies with the
throughput rate. When using very slow throughput rates
and as fast an SCLK frequency as possible, the various power-
down options can be used to make significant power savings.
However, the AD7357 quiescent current is low enough that
even without using the power-down options, there is a noticeable
variation in power consumption with sampling rate. This is true
whether a fixed SCLK value is used or if it is scaled with the sam-
pling rate. Figure 29 shows a plot of power vs. throughput rate
when operating in normal mode for a fixed maximum SCLK
frequency and an SCLK frequency that scales with the sampling
rate. The internal reference was used for Figure 29.
Modes of Operation
th
38
34
30
26
22
18
14
10
SCLK falling edge; the second and third dummy cycles
0
80MHz SCLK
Figure 29. Power vs. Throughput Rate
1000
section).
THROUGHPUT (kSPS)
2000
VARIABLE SCLK
3000
Figure 27
4000
AD7357
and