pca9691 NXP Semiconductors, pca9691 Datasheet - Page 8

• Manufacturer Part Number: pca9691
• Description: 8-bit A/d And D/a Converter
• Manufacturer: NXP Semiconductors

NXP Semiconductors
PCA9691_1
Product data sheet
In order to release the DAC for a successive approximation A/D conversion cycle, the
unity gain amplifier is equipped with a sample and hold circuit. This circuit holds the output
voltage while executing the A/D conversion.
The formula for the output voltage supplied to the analog output pin AOUT is shown in
Figure
The waveforms of a D/A conversion sequence are shown in
With the rising edge of the 8th clock bit the DAC register is filled with a new value D7 to
D0. After some delay the voltage at the analog output starts to change from the previous
value to the new value.
This delay is random but stays within the following limits:
Where T
Remark: When AOUT starts changing, the DAC settling time t
is required for AOUT to reach a new accurate value.
Fig 6.
•
•
Minimum 8T
Maximum 18T
7.
osc
DAC resistor divider chain
is the oscillator period (oscillator frequency is given in
osc
osc
AGND
from the rising edge of the 8th bit
VREF
from the rising edge of the acknowledge bit (9th bit)
Rev. 01 — 8 April 2008
PCA9691
R256
R255
R3
R2
R1
DAC out
FF
02
01
00
DECODER
TAP
SAMPLE
HOLD
AND
D7
D6
D0
unity gain
amplifier
8-bit A/D and D/A converter
Figure
s(DAC)
001aag467
AOUT
Table
8.
(specified in
PCA9691
© NXP B.V. 2008. All rights reserved.
6).
Table
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