AD5533BBCZ-1 データシートの表示（PDF） - Analog Devices
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AD5533BBCZ-1 Datasheet PDF : 16 Pages
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AD5533B
Reset Function
The reset function on the AD5533B can be used to reset all
nodes on this device to their power-on-reset condition. This is
implemented by applying a low-going pulse of between 90 ns and
200 ns to the TRACK/RESET pin on the device. If the applied
pulse is less than 90 ns, it is assumed to be a glitch and no opera-
tion takes place. If the applied pulse is wider than 200 ns, this pin
adopts its track function on the selected channel, VIN is switched to
the output buffer, and an acquisition on the channel will not occur
until a rising edge of TRACK.
TRACK Function
Normally in ISHA mode of operation, TRACK is held high and
the channel begins to acquire when it is addressed. However, if
TRACK is low when the channel is addressed, VIN is switched
to the output buffer and an acquisition on the channel will not
occur until a rising edge of TRACK. At this stage the BUSY pin
will go low until the acquisition is complete, at which point the
DAC assumes control of the voltage to the output buffer and
VIN is free to change again without affecting this output value.
This is useful in an application where the user wants to ramp up
VIN until VOUT reaches a particular level (Figure 7). VIN does
not need to be acquired continuously while it is ramping up.
TRACK can be kept low and only when VOUT has reached its
desired voltage is TRACK brought high. At this stage, the
acquisition of VIN begins.
In the example shown, a desired voltage is required on the output
of the pin driver. This voltage is represented by one input to a
comparator. The microcontroller/microprocessor ramps up the
input voltage on VIN through a DAC. TRACK is kept low while
the voltage on VIN ramps up so that VIN is not continually
acquired. When the desired voltage is reached on the output of the
pin driver, the comparator output switches. The µC/µP then
knows what code is required to be input in order to obtain the
desired voltage at the DUT. The TRACK input is now brought
high and the part begins to acquire VIN. BUSY goes low until VIN
has been acquired. When BUSY goes high, the output buffer
is switched from VIN to the output of the DAC.
MODES OF OPERATION
The AD5533B can be used in three different modes. These modes
are set by two mode bits, the first two bits in the serial word.
The 01 option (DAC Mode) is not available for the AD5533B.
For information on this mode, refer to the AD5532B data sheet.
If you attempt to set up DAC Mode, the AD5533B will enter a
test mode and a 24-clock write will be necessary to clear this.
Mode Bit 1
0
0
1
1
Table II. Modes of Operation
Mode Bit 2 Operating Mode
0
ISHA Mode
1
DAC Mode (Not Available)
0
Acquire and Readback
1
Readback
1. ISHA Mode
In this standard mode, a channel is addressed and that channel
acquires the voltage on VIN. This mode requires a 10-bit
write (see Figure 3) to address the relevant channel
(VOUT0–VOUT31, offset channel, or all channels). MSB is
written first.
2. Acquire and Readback Mode
This mode allows the user to acquire VIN and read back the
data in a particular DAC register. The relevant channel is
addressed (10-bit write, MSB first) and VIN is acquired in 16 µs
(max). Following the acquisition, after the next falling edge of
SYNC, the data in the relevant DAC register is clocked out
onto the DOUT line in a 14-bit serial format (see Figure 4).
During readback, DIN is ignored. The full acquisition time
must elapse before the DAC register data can be clocked out.
3. Readback Mode
Again, this is a readback mode but no acquisition is performed.
The relevant channel is addressed (10-bit write, MSB first) and
on the next falling edge of SYNC, the data in the relevant DAC
register is clocked out onto the DOUT line in a 14-bit serial format
(see Figure 4). The user must allow 400 ns (min) between the
last SCLK falling edge in the 10-bit write and the falling edge
of SYNC in the 14-bit readback. The serial write and read words
can be seen in Figure 8.
This feature allows the user to read back the DAC register
code of any of the channels. Readback is useful if the system
has been calibrated and the user wants to know what code in
the DAC corresponds to a desired voltage on VOUT.
INTERFACES
Serial Interface
The SER/PAR pin is tied high to enable the serial interface and
to disable the parallel interface. The serial interface is controlled
by four pins as follows:
SYNC, DIN, SCLK
Standard 3-wire interface pins. The SYNC pin is shared
with the CS function of the parallel interface.
DOUT
Data out pin for reading back the contents of the DAC registers.
The data is clocked out on the rising edge of SCLK and is
valid on the falling edge of SCLK.
Mode Bits
There are four different modes of operation as described above.
Cal Bit
When this is high, all 32 channels acquire VIN simultaneously. The
acquisition time is then 45 µs (typ) and accuracy may be reduced.
This bit is set low for normal operation.
Offset_Sel Bit
If this bit is set high, the offset channel is selected and bits
A4–A0 are ignored.
Test Bit
This must be set low for correct operation of the part.
A4–A0 Bit
Used to address any one of the 32 channels (A4 = MSB of
address, A0 = LSB).
–12–
REV. A
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