X9530-B15I INTERSIL [Intersil Corporation], X9530-B15I Datasheet - Page 8

• Manufacturer Part Number: X9530-B15I
• Description: Temperature Compensated Laser Diode Controller
• Manufacturer: INTERSIL [Intersil Corporation]

VOLTAGE REFERENCE
The voltage reference to the A/D and D/A converters
on the X9530, may be driven from the on-chip voltage
reference, or from an external source via the VRef pin.
Bit VRM in Control Register 0 selects between the two
options (See Figure 2).
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
Control Register 0 must be set to “1”.
Figure 2. Voltage Reference Structure
A/D CONVERTER
The X9530 contains a general purpose, on-chip, 6-bit
Analog to Digital (A/D) converter whose output is
available at the Status Register as bits AD[5:0]. By
Figure 3. A/D Converter Block Diagram
A/D Converter Input
VRef Pin
From VRef
VRM: bit 2 in Control register 0.
8
Generator
A/D Converter and
D/A Converters reference
Ramp
Reference
On-chip
Voltage
Comparator
X9530
Clock
Conversion Reset
default these output bits are used to select a row in the
look-up tables associated with the X9530’s Current
Generators. When bit ADCfiltOff is “0” (default), bits
AD[5:0] are updated each time the ADC performs four
consecutive conversions with the same exact result.
When bit ADCfiltOff is “1”, these bits are updated after
every ADC conversion.
A block diagram of the A/D converter is shown in
Figure 3. The voltage reference input (see “VOLTAGE
REFERENCE”
amplitude 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 (0
(63
The A/D converter input voltage range (VIN
from 0 V to V(VRef).
A/D Converter Input Select
The input signal to the A/D converter on the X9530,
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 4). 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”.
10
).
Encode Logic
Control and
10
), and a full scale output value of 3Fh
for
details),
6
sets
A/D Converter
and Status
the
(To LUTs
Register)
Output
maximum
March 10, 2005
ADC
FN8211.0
) is