AD7495BRZ Analog Devices Inc, AD7495BRZ Datasheet - Page 19

• Manufacturer Part Number: AD7495BRZ
• Description: ADC Single SAR 1MSPS 12-Bit Serial 8-Pin SOIC N
• Manufacturer: Analog Devices Inc

Specifications of AD7495BRZ

• Package: 8SOIC N
• Resolution: 12 Bit
• Sampling Rate: 1000 KSPS
• Architecture: SAR
• Number Of Analog Inputs: 1
• Digital Interface Type: Serial (SPI, QSPI, Microwire)
• Input Type: Voltage
• Signal To Noise Ratio: 68 dB
• Polarity Of Input Voltage: Unipolar
• Number Of Bits: 12
• Sampling Rate (per Second): 1M
• Data Interface: DSP, MICROWIRE™, QSPI™, Serial, SPI™
• Number Of Converters: 1
• Power Dissipation (max): 10.5mW
• Voltage Supply Source: Single Supply
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (0.154", 3.90mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

POWER VS. THROUGHPUT RATE
By using the partial power-down mode on the AD7475/
AD7495 when not converting, the average power consumption
of the ADC decreases at lower throughput rates. Figure 24
shows how, as the throughput rate is reduced, the part remains
in its partial power-down state longer and the average power
consumption over time drops accordingly.
For example, if the AD7495 is operated in a continuous
sampling mode with a throughput rate of 100 kSPS and an
SCLK of 20 MHz (V
power-down mode between conversions, then the power
consumption is calculated as follows. The maximum power
dissipation during normal operation is 13 mW (V
the power-up time from partial power-down is one dummy
cycle, that is, 1 μs, and the remaining conversion time is another
cycle, that is, 1 μs, then the AD7495 can be said to dissipate
13 mW for 2 μs during each conversion cycle. For the
remainder of the conversion cycle, 8 μs, the part remains in
partial power-down mode. The AD7495 dissipates 1.15 mW for
the remaining 8 μs of the conversion cycle. If the throughput
rate is 100 kSPS, and the cycle time is 10 μs, the average power
dissipated during each cycle is (2/10) × (13 mW) + (8/10) ×
(1.15 mW) = 3.52 mW. If V
device is again in partial power-down mode between conver-
sions, the power dissipated during normal operation is 6 mW.
0.001
0.01
100
0.1
10
1
Figure 24. Power vs. Throughput for Partial Power Down
0
AD7475 5V
SCLK = 20MHz
50
DD
100
= 5 V), and the device is placed in partial
THROUGHPUT (kSPS)
AD7495 5V
SCLK = 20MHz
DD
150
AD7475 3V
SCLK = 20MHz
= 3 V, SCLK = 20 MHz and the
200
250
AD7495 3V
SCLK = 20MHz
300
DD
= 5 V). If
350
Rev. B | Page 19 of 24
The AD7495 dissipates 6 mW for 2 μs during each conversion
cycle and 0.69 mW for the remaining 8 μs where the part is in
partial power-down. With a throughput rate of 100 kSPS, the
average power dissipated during each conversion cycle is (2/10)
× (6 mW) + (8/10) × (0.69 mW) = 1.752 mW. Figure 24 shows
the power vs. throughput rate when using partial power-down
mode between conversions with both 5 V and 3 V supplies for
both the AD7475 and AD7495. For the AD7475, partial power-
down current is lower than that of the AD7495.
Full power-down mode is intended for use in applications with
slower throughput rates than required for partial power-down
mode. It is necessary to leave 650 μs for the AD7495 to be fully
powered up from full power-down before initiating a conver-
sion. Current consumptions between conversions is typically
less than 1 μA.
Figure 25 shows a typical graph of current vs. throughput for
the AD7495 while operating in different modes. At slower
throughput rates, for example, 10 SPS to 1 kSPS, the AD7495
was operated in full power-down mode. As the throughput rate
increased, up to 100 kSPS, the AD7495 was operated in partial
power-down mode, with the part being powered down between
conversions. With throughput rates from 100 kSPS to 1 MSPS,
the part operated in normal mode, remaining fully powered up
at all times.
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
10
Figure 25. Typical AD7495 Current vs. Throughput
POWER-DOWN
FULL
100
THROUGHPUT (SPS)
1k
POWER-DOWN
PARTIAL
10k
AD7475/AD7495
V
DD
100k
= 5V
NORMAL
1M