X96012 Datasheet, PDF (15/27 Pages) Intersil Corporation – Universal Sensor Conditioner with Dual Look Up Table Memory and DACs

X96012
VOLTAGE REFERENCE
The voltage reference to the A/D and D/A converters
on the X96012, may be driven from the on-chip volt-
age reference, or from an external source via the VRef
pin. Bit VRM in Control Register 0 selects between the
two options (See Figure 5).
The default value of VRM is “0”, which selects the
internal reference. When the internal reference is
selected, it’s output voltage is also an output at pin
VRef with a nominal value of 1.21 V. If an external
voltage reference is preferred, the VRM bit of the Con-
trol Register 0 must be set to “1”.
Figure 5. Voltage Reference Structure
VRM: bit 2 in Control register 0.
VRef Pin
On-chip
Voltage
Reference
A/D Converter and
D/A Converters reference
A/D CONVERTER
The X96012 contains a general purpose, on-chip, 8-bit
Analog to Digital (A/D) converter whose output is avail-
able at the Status Register as bits AD[7:0]. By default
these output bits are used to select a row in the look-
up tables associated with the X96012’s Current Gen-
erators. When bit ADCfiltOff is “0” (default), bits
AD[7:0] are updated each time the ADC performs four
consecutive conversions with the same exact result at
the 6 MSBs. When bit ADCfiltOff is “1”, these bits are
updated after every ADC conversion.
A block diagram of the A/D converter is shown in Fig-
ure 6. The voltage reference input (see “VOLTAGE
REFERENCE” for details), sets the maximum ampli-
tude of the ramp generator output. The A/D converter
input signal (see “A/D Converter Input Select” below
for details) is compared to the ramp generator output.
The control and encode logic produces a binary
encoded output, with a minimum value of 00h (0₁₀),
and a full scale output value of FFh (255₁₀).
The A/D converter input voltage range (VIN_ADC) is
from 0 V to V(VRef).
A/D Converter Input Select
The input signal to the A/D converter on the X96012,
may be the output of the on-chip temperature sensor,
or an external source via the VSense pin. Bit ADCIN in
Control register 0 selects between the two options
(See Figure 7). It’s default value is “0”, which selects
the internal temperature sensor.
If an external source is intended as the input to the
A/D converter, the ADCIN bit of the Control register 0
must be set to “1”.
Figure 6. A/D Converter Block Diagram
A/D Converter Input
From VRef
Ramp
Generator
Comparator
8
Control and
Encode Logic
Conversion Reset
A/D Converter
Output
(To LUTs
and Status
Register)
Clock
15
FN8216.0
March 10, 2005