pca9691 NXP Semiconductors, pca9691 Datasheet - Page 12

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

NXP Semiconductors
PCA9691_1
Product data sheet
7.5 Reference voltage
7.6 Oscillator
For the D/A and A/D conversion either a stable external voltage reference or the supply
voltage has to be applied to the resistor divider chain (pins VREF and AGND). Pin AGND
has to be connected to the system analog ground and may have a DC off-set with
reference to V
A low frequency may be applied to pins VREF and AGND. This allows the use of the DAC
as a one-quadrant multiplier (see
The ADC may also be used as a one- or two-quadrant analog divider. The analog input
voltage is divided by the reference voltage. The result is converted to a binary code. In this
application the user has to keep the reference voltage stable during the conversion cycle.
An on-chip oscillator generates the clock signal required for the A/D conversion cycle and
for refreshing the auto-zeroed buffer amplifier. When using this oscillator pin EXT has to
be connected to V
(see
disabled. In this case the output pin OSC = LOW.
The oscillator starts when a start condition is sent via the I
address is recognized as valid the oscillator continues to run. If the received address is
not recognized the oscillator stops.
If a stop condition occurs the oscillator is stopped unless pin AOUT is enabled.
Fig 12. A/D conversion characteristics of differential inputs
Section
7.2). However, in normal operation it is recommended that output pin OSC is
SS
128
.
SS
127
. The oscillator frequency divided by 4 is available at output pin OSC
Rev. 01 — 8 April 2008
2
ADC (hex)
Figure 11
1
7E
7F
00
02
01
FE
81
80
FF
0
and
1
Figure
2
V
LSB
23).
=
2
C-bus interface. If the received
126
V
8-bit A/D and D/A converter
VREF
256
127
V
AGND
PCA9691
© NXP B.V. 2008. All rights reserved.
V
AIN+
V
LSB
001aah588
V
AIN
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