EVAL-AD5620EB AD [Analog Devices], EVAL-AD5620EB Datasheet - Page 19

• Manufacturer Part Number: EVAL-AD5620EB
• Description: Single, 12-/14-/16-Bit nanoDAC with 5 ppm/C On-Chip Reference in SOT-23
• Manufacturer: AD [Analog Devices]

POWER-ON RESET
The AD5620/AD5640/AD5660 family contains a power-on
reset circuit that controls the output voltage during power-up.
The AD5620/AD5640/AD5660-1-2 DAC output powers up to
0 V, and the AD5620/AD5660-3 DAC output powers up to
midscale. The output remains at this level until a valid write
sequence is made to the DAC, which is useful in applications
where it is important to know the state of the DAC output while
it is in the process of powering up.
POWER-DOWN MODES
The AD5620/AD5640/AD5660 have four separate modes of
operation. These modes are software-programmable by setting
two bits in the control register. Table 6 and Table 7 show how
the state of the bits corresponds to the operating mode of the
device.
Table 6. Modes of Operation for the AD5660
DB17
0
0
1
1
Table 7. Modes of Operation for the AD5620/AD5640
DB15
0
0
1
1
When both bits are set to 0, the part works normally with its
normal power consumption of 550 μA at 5 V. However, for the
three power-down modes, the supply current falls to 480 nA
at 5 V (200 nA at 3 V). Not only does the supply current fall,
but the output stage is internally switched from the output of
the amplifier to a resistor network of known values. The
advantage is that the output impedance of the part is known
while the part is in power-down mode. There are three options:
the output is connected internally to GND through a
1 kΩ or a 100 kΩ resistor, or it is left open-circuited (three-
stated). The output stage is shown in Figure 44.
DB16
0
1
0
1
DB14
0
1
0
1
AD5660 Operating Mode
Normal operation
Power-down modes:
AD5620/AD5640 Operating Mode
Normal operation
Power-down modes:
1 kΩ to GND
100 kΩ to GND
Three-state
1 kΩ to GND
100 kΩ to GND
Three-state
Rev. A | Page 19 of 24
The bias generator, output amplifier, reference, resistor string,
and other associated linear circuitry are all shut down when
power-down mode is activated. However, the contents of the
DAC register are unaffected when in power-down. The time to
exit power-down is typically 5 μs for V
See Figure 23.
MICROPROCESSOR INTERFACING
AD5660-to-Blackfin® ADSP-BF53x Interface
Figure 45 shows a serial interface between the AD5660 and the
Blackfin ADSP-BF53x microprocessor. The ADSP-BF53x
processor family incorporates two dual-channel synchronous
serial ports, SPORT1 and SPORT0, for serial and multi-
processor communications. Using SPORT0 to connect to the
AD5660, the setup for the interface is as follows: DT0PRI drives
the DIN pin of the AD5660, while TSCLK0 drives the SCLK of
the part and SYNC is driven from TFS0.
1
ADDITIONAL PINS OMITTED FOR CLARITY
ADSP-BF53x
STRING DAC
RESISTOR
Figure 45. AD5660-to-Blackfin ADSP-BF53x Interface
Figure 44. Output Stage During Power-Down
TSCLK0
DTOPRI
TFS0
1
POWER-DOWN
AMPLIFIER
AD5620/AD5640/AD5660
CIRCUITRY
DD
= 5 V and V
AD5660
SYNC
DIN
SCLK
NETWORK
RESISTOR
1
V
OUT
DD
= 3 V.