EXAR Corporation, 48720 Kato Road, Fremont, CA 94538

(510) 668-7000

FAX (510) 668-7017

www.exar.com

XRD9827

12-Bit Linear CIS/CCD Sensor

Signal Processor with Serial Control

May 2000-3

FEATURES

12-Bit Resolution, No Missing Codes

One-channel 6MSPS Pixel Rate

Triple-channel 2MSPS Pixel Rate

6-Bit Programmable Gain Amplifier

8-Bit Programmable Offset Adjustment

CIS or CCD Compatibility

Internal Clamp for CIS or CCD AC Coupled

Configurations

3.3V or 5V Operation & I/O Compatibility

Serial Load Control Registers

Low Power CMOS: 200mW-typ

Low Cost 20-Lead Packages

USB Compliant

APPLICATIONS

Color and Grayscale Flatbed Scanners

Color and Grayscale Sheetfed Scanners

Multifunction Peripherals

Digital Color Copiers

General Purpose CIS or CCD Imaging

Low Cost Data Acquisition

Simple and Direct Interface to Canon 600 DPI

Sensors

ORDERING INFORMATION

Package Type

Temperature Range

Part Number

20-Lead SOIC

0°C to +70°C

XRD9827ACD

20-Lead SSOP

0°C to +70°C

XRD9827ACU

GENERAL DESCRIPTION

The XRD9827 is a complete linear CIS or CCD sensor
signal processor on a single monolithic chip. The
XRD9827 includes a high speed 12-Bit resolution ADC,
a 6-Bit Programmable Gain Amplifier with gain adjust-
ment of 1 to 10, and 8-Bit programmable input referred
offset calibration range of 800mV.

In the CCD configuration the input signal is AC coupled
with an external capacitor. An internal clamp sets the
black level. In the CIS configuration, the clamp switch
can be disabled and the CIS output signal is DC coupled
from the CIS sensor to the XRD9827. The CIS signal
is level shifted to VRB in order to use the full range of
the ADC. In the CIS configuration the input can also be

AC coupled similar to the CCD configuration. This
enables CIS signals with large black levels to be
internally clamped to a DC reference equal to the black
level. The DC reference is internally subtracted from
the input signal.

The CIS configuration can also be used in other appli-
cations that do not require CDS function, such as low
cost data acquisition.

Rev. 1.20

XRD9827

Rev. 1.20

PIN CONFIGURATION

A V D D

V R E F +

X R D 9 8 2 7 A C D

R E D

G R N

B L U

V D C E X T

A G N D

D V D D

D B 0

D B 1

D B 2

D B 4

D G N D

A D C C L K

D B 3

D B 5 / S C L K

D B 6 / S D A T A

D B 7 / L D

C L A M P

S Y N C H

20-Lead SOIC

PIN DESCRIPTION

Pin #

Symbol

Description

DVDD

Digital VDD (for Output Drivers)

DB0

Data Output Bit 0

DB1

Data Output Bit 1

DB2

Data Output Bit 2

DB3

Data Output Bit 3

DB4

Data Output Bit 4

DB5/SCLK

Data Output Bit 5 & Data Input SCLK

DB6/SDATA

Data Output Bit 6 & Data Input SDATA

DB7/LD

Data Output Bit 7 & LD

DGND

Digital Ground (for Output Drivers)

ADCCLK

A/D Converter Clock

CLAMP

Clamp and Video Sample Clock

SYNCH

Start of New Line and Serial Data Input Control

AGND

Analog Ground

VREF+

A/D Positive Reference for Decoupling Cap

VDCEXT

External DC Reference

BLU

Blue Input

GRN

Green Input

RED

Red Input

AVDD

Analog Power Supply

XRD9827

Rev. 1.20

ELECTRICAL CHARACTERISTICS
Test Conditions: AV

=DV

=5V, ADCCLK=6MHz, 50% Duty Cycle, T

=25°C unless otherwise specified.

Symbol

Parameter

Min.

Typ.

Max.

Unit

Conditions

Power Supplies

Analog Power Supply

3.0

3.3

5.5

(Note 2)

Digital I/O Power Supply

3.0

3.3

5.5

< AV

Supply Current

=5V

IDD

Power Down Power Supply Current

=5V

ADC Specifications

RES

Resolution

Bits

Maximum Sampling Rate

MSPS

DNL

Differential Non-Linearity

±0.5

LSB

INL

Integral Non-Linearity

±1.0

LSB

MON

Monotonicity

Yes

Top Reference Voltage

3.50

3.70

3.90

Bottom Reference Voltage

/10

REF

Differential Reference Voltage

0.3

0.67AV

- V

)

Ladder Resistance

300

600

780

PGA & Offset DAC Specifications

PGARES

PGA Resolution

Bits

PGAG

MIN

Minimum Gain

0.950

1.0

1.050

V/V

PGAG

MAX

Maximum Gain

9.5

10.0

10.50

V/V

PGAGD

Gain Adjustment Step Size

0.14

V/V

BLACK

Black Level Input Range

-100

500

DC Configuration

DACRES

Offset DAC Resolution

Bits

OFF

MIN

Minimum Offset Adjustment

-250

-200

-150

Mode 111, D5=0 (Note 1)

OFF

MAX

Maximum Offset Adjustment

+500

+600

+700

Mode 111, D5=0

OFF

MIN

Minimum Offset Adjustment

-450

-400

-350

Mode 111, D5=1 (Note 1)

OFF

MAX

Maximum Offset Adjustment

+350

+400

+450

Mode 111, D5=1

OFF

Offset Adjustment Step Size

3.14

Note 1:

The additional ±100 mV of adjustment with respect to the black level input range is needed to compensate
for any additional offset introduced by the XRD9827 Buffer/PGA internally.

Note 2:

It is not recommended to operate the part between 3.6V and 4.4V.

XRD9827

Rev. 1.20

ELECTRICAL CHARACTERISTICS (CONT'D)
Test Conditions: AV

=DV

=5V, ADCCLK=6MHz, 50% Duty Cycle, T

=25°C unless otherwise specified.

Symbol

Parameter

Min.

Typ.

Max.

Unit

Conditions

Buffer Specifications

Input Leakage Current

100

CIN

Input Capacitance

VIN

AC Input Voltage Range

-1.4

CIS AC; INT V

DCREF

Config Reg

=> XXX010XX

Gain=1 (Note 1)

AC Input Voltage Range

REF

CCD AC; INT V

DCREF

Config Reg

=> XXX011XX

Gain=1 (Note 1)

VIN

DC Input Voltage Range

-0.1

-1.4

CIS DC; INT V

DCREF

Config Reg

=> XXX000XX

Gain=1 (Note 2)

DC Input Voltage Range

DCEXT

-0.1

DCEXT

CIS DC; EXT V

DCREF

REF

Config Reg

=> XXX100XX

Gain=1 (Note 3)

DCEXT

+DV

REF

< AV

DCEXT

External DC Reference

0.3

CIS DC; EXT V

DCREF

Config Reg

=> XXX100XX

VIN

Input Bandwidth (Small Signal)

MHz

VIN

Channel to Channel Crosstalk

-60

-50

=3MHz

Internal Clamp Specifications

CLAMP

Clamp Voltage

AGND

CIS (AC) Config

3.5

CCD (AC) Config

INT

Clamp Switch On Resistance

100

150

OFF

Clamp Switch Off Resistance

Note 1: VIN

is the signal swing before the external capacitor tied to the MUX inputs.

Note 2: The -0.1V minimum is specified in order to accommodate black level signals lower than the external DC

reference (clamp) voltage.

Note 3: The V

DCEXT

-0.1V minimum is specified in order to accommodate black level signals lower than the external DC

reference voltage.

XRD9827

Rev. 1.20

ELECTRICAL CHARACTERISTICS (CONT'D)

Test Conditions: AV

=DV

= 5V, ADCCLK=6MHz, 50% Duty Cycle, T

=25°C unless otherwise specified.

Symbol

Parameter

Min.

Typ.

Max.

Unit

Conditions

System Specifications (MUX + Buffer + PGA + ADC)

Note 1

SYS

DNL

System DNL

-1.0

±0.5

+2.3

LSB

SYS

LIN

System Linearity

±6.0

LSB

SYS

System Gain Error

-5.0

+5.0

IRN

Input Referred Noise

1.5

rms

Gain=1

Input Referred Noise

0.5

rms

Gain=10

System Timing Specifications

tcklw

ADCCLK Low Pulse Width

tckhw

ADCCLK High Pulse Width

tckpd

ADCCLK Period

120

166

tsypw

SYNCH Pulse Width

trars

Rising ADCCLK to rising

SYNCH must rise equal to

SYNCH

or after ADCCLK, See Figure 18

tclpw

CLAMP Pulse Width

Note 2

Write Timing Specifications

tsclkw

SCLK Pulse Width

tdz

LD Low to SCLK High

tds

Input Data Set-up Time

tdh

Input Data Hold Time

tdl

SCLK High to LD High

ADC Digital Output Specifications

tap

Aperture Delay

tdv

Output Data Valid

tsa

SYNCH to ADCCLK

3ch Pixel Md

tlat

Latency

cycles

Config 00, 11

tlat

Latency

pixels

Config 01, 10

Digital Input Specifications

Input High Voltage

-2.5

Input Low Voltage

High Voltage Input Current

Low Voltage Input Current

Input Capacitance

Note 1:

System performance is specified for typical digital system timing specifications.

Note 2:

The actual minimum `tclpw' is dependent on the external capacitor value, the CIS output impedance.
During `clamp' operation, sufficient time needs to be allowed for the external capacitor to charge up to the
correct operating level. Refer to the description in Theory of Operation, CIS Config.

XRD9827

Rev. 1.20

THEORY OF OPERATION

CIS Configuration (Contact Image Sensor)

The XRD9827 has two configurations for CIS applications. Each configuration is set by the control registers
accessed through the serial port.

Mode 1. DC Coupled

If the CIS does not have leading or trailing black pixels as shown in Figure 2, then DC couple the CIS output to the
XRD9827 input.

Optically Shielded

Pixels

Valid Pixels

Adjust the offset of the CIS (-100 mV to 500 mV) by setting the internal registers of the XRD9827 to set the black
pixel value when the LEDs of the CIS are off. When the LEDs are on, use the XRD9827 Programmable Gain to
maximize the ADCs dynamic range. Figure 3 shows a typical application for a CIS with an offset of -100mV to 500mV.

Figure 2. Typical Output CIS Mode

XRD9827

Rev. 1.20

VRT

VRB

VDD

RED

XRD9827

N/C

The input is added to VRB before the signal passes
through the ADC. If the CIS output is zero, then the
output of the ADC will be zero code. This enables the
CIS to be referenced to the bottom ladder reference
voltage to use the full range of the ADC.

Some CIS sensors have an output with an offset voltage
of greater than 500mV. If the CIS output is beyond the

offset range of the XRD9827 (see Offset Control DAC,
Pg. 28) set the internal mode registers to external
reference. An external reference voltage equal to the
value of the CIS offset voltage can be applied to
VDCEXT (Figure 4) in order to meet the dynamic range
of the XRD9827. Figure 4 is a diagram of the XRD9827
in the external reference mode for CIS, DC coupled
applications.

Figure 3. Application with Offset in the Range (-100mv to 500mv)

XRD9827

Rev. 1.20

CIS Mode Timing -- DC Coupled

(CLAMP disabled)

ADCCLK

tckhw

tcklw

tckpd

tap

Pixel N-1

Pixel N

tdv

Pixel N+1

CIS

tdv

[5:0]

[11:6]

N-8

MSB

N-8

LSB

N-7

MSB

N-7

LSB

N-6

MSB

N-6

LSB

N-5

MSB

N-5

LSB

Figure 6. Timing Diagram for Figure 5

ADCCLK

Events

ADC Sample & PGA Start Tracking next Pixel

MSB Data Out

LSB Data Out

ADC Track PGA Output

ADC Hold/Convert

Table 1.

Mode 2. AC Coupled

If the CIS signal has a black reference for the video
signal, an external capacitor C

EXT

is used. When

CLAMP (clamp) pin is set high an internal switch allows

one side of the external capacitor to be set to ground.
It then is level shifted to correspond to the bottom ladder
reference voltage of the ADC (Figure 7).

XRD9827

Rev. 1.20

VRT

VRB

VDD

XRD9827

CLAMP

RINT

RED

U
X

REXT CEXT

N/C

Therefore, Tc =1/R

INT

EXT

If the input to the external capacitor has a source
impedance (R

EXT

), then:

=1/(R

INT

EXT

This value corresponds to the black reference of the
image sensor. When the CLAMP pin is set back to low,
the ADC samples the video signal with respect to the
black reference. The typical value for the external
capacitor is 100pF. This value should be adjusted
according to the time constant (Tc) needed in a particu-
lar application. The CLAMP pin has an internal 150 ohm
impedance (R

INT

) which is in series with the external

capacitor (C

EXT

Figure 7. CIS AC Coupled Application

XRD9827

Rev. 1.20

CIS Mode Timing -- AC Coupled

(CLAMP enabled)

ADCCLK

tckhw

tcklw

tckpd

tap

Pixel N-1

Pixel N

tdv

Pixel N+1

CIS

tdv

[5:0]

[11:6]

N-8

LSB

N-7

LSB

N-6

LSB

N-5

LSB

CLAMP

tclpw

MSB

Figure 9. Timing Diagram for Figure 8

ADCCLK

Events

ADC Sample & PGA Start Track of next Pixel

MSB Data Out

LSB Data Out

ADC Track PGA Output

ADC Hold/Convert

Table 3.

CLAMP

Events

PGA Tracks V

CLAMP

& C

EXT

is Charged to

BLACK

- V

CLAMP

, which is equal to V

BLACK

PGA Tracks VIN

Table 4.

XRD9827

Rev. 1.20

Internal CIS Reference Circuit (DB 4 = 1)

The XRD9827 has an internal register reserved for
interfacing to the Canon CIS model number CVA-
60216K. When this register is selected, the VDCEXT
(Pin 16) becomes an output voltage of 1.24 volts. This
voltage can be directly connected to the VREF (Pin 5)
of the Canon sensor. This reduces the amount of

Figure 10. Typical Application Circuitry Internal CIS Reference Circuit Mode

CANON CIS Sensor, Model #CVA=60216k

components needed for biasing the Canon CIS sensor
(the external diodes and resistors typically used in this
application have been included inside the XRD9827 for
this mode of operation). Below is a typical application
circuit using the XRD9827 and the Canon CVA-60216K
CIS sensor.

AGND

DVDD (3V - 5V)

VCC (5V)

AVDD

DGND

AGND

DGND

DVDD (3V - 5V)

ASIC

DIGITAL

N/C

CANON CIS

SENSOR

0.1uF

0.01uF

0.1uF

0.01uF

0.1uF

XRD9827

DVDD

DB0

DB1

DB2

DB3

DB4

DB5/SCLK

DB6/SDATA

DB7/LD

DGND

ADCCLK

CLAMP

SYNCH

AGND

VREF+

VDCEXT

BLU

GRN

RED

AVDD

CVA-60216K

VOUT

MODE

AGND

VCC

VREF

CLK

LED COM

LED BLU

LED GRN

LED RED

FGND

10K

47uF

NPN

0.01uF

100uF

XRD9827

Rev. 1.20

Figure 11. Typical Application Circuitry Internal CIS Rotating Gain

and Offset Line-By-Line

CIS Line-By-Line Rotating Gain and Offset
(Configuration DB1 = 1, DB0 = 1)

Line-by-line rotating gain and offset minimizes the
amount of write cycles per scan. Pre-loaded values of
gain and offset can be loaded for each color before the
first line is scanned. Each gain and offset is cycled

AVDD

AGND

DGND

VCC (5V - 15V)

DVDD (3V - 5V)

ASIC

DIGITAL

N/C

0.01uF

0.1uF

XRD9827

DVDD

DB0

DB1

DB2

DB3

DB4

DB5/SCLK

DB6/SDATA

DB7/LD

DGND

ADCCLK

CLAMP

SYNCH

AGND

VREF+

VDCEXT

BLU

GRN

RED

AVDD

0.01uF

through line-by-line so that the gain and offset do not
have to be loaded in between lines. Below is the typical
application circuit and timing for this configuration.

XRD9827

Rev. 1.20

Figure 12. Timing Diagram for Figure 11

CCD Configuration (Charge Coupled Device)

Mode 1. AC Coupled

In the CCD configuration of operation, an external
capacitor needs to be chosen according to the equa-
tions below. The typical value for the external capacitor
is 100pF. This value should be adjusted according to
the time constant (Tc) needed in a particular applica-
tion. The CLAMP pin has an internal 150 ohm imped-
ance (R

INT

) which is in series with the external capacitor

EXT

Therefore, Tc =1/R

INT

EXT

If the input to the external capacitor has a load imped-
ance (R

EXT

), then

=1/(R

INT

EXT

CIS Rotating Gain and Offset

Line-By-Line (Md 11)

ADCCLK

CIS

SYNCH

GAIN/

OFFSET

Red Pixel Line Scan

Grn Pixel Line Scan

Blu Pixel Line Scan

Red Gain/Offset Cycle

Grn Gain/Offset Cycle

Blu Gain/Offset Cycle

Reset Internal Mux Color to Red Channel (LD = 110YYYYYY11)

tsa

tsypw

Note: Y = Previous State

Tri-State (SYNCH = LO)

When CLAMP (clamp) pin is set high an internal switch
allows one side of the external capacitor to be set to
VRT (Figure 13). This value corresponds to the black
reference of the CCD. When the CLAMP pin is set back
to low, the ADC samples the video signal with respect
to the black reference. The difference between the
black reference and the video signal is the actual pixel
value of the video content. Since this value is refer-
enced to the top ladder reference voltage of the ADC a
zero input signal would yield a full scale output code.
Therefore, the output of the conversion is inverted
(internally) to correspond to zero scale output code.

XRD9827

Rev. 1.20

Area or Linear CCD Applications

Figure 13 is a block diagram for applications with Area
or Linear CCDs (The timing for Area CCDs and B/W
CCDs is the same). For Area or Linear CCD applica-
tions, a global offset is loaded into the serial port at the
beginning of a line. The gain is set to adjust for the
highest color intensity of the CCD output. Once the

pixel values have been sampled, the gain and offset are
adjusted at the beginning of the next line. For example,
if there is a line-to-line variation between the black
reference pixels, the offset is adjusted. The gain is
always adjusted for the highest color intensity.

Figure 13. CCD AC Coupled Application

VRT

VRB

VDD

RED

XRD9827

CLAMP

AREA

LINEAR

CCD

N/C

XRD9827

Rev. 1.20

tdv

AREA, LINEAR or B/W CCD -- AC Coupled

(CLAMP Enabled)

Pixel N-1

Pixel N

Pixel N+1

CCD

Channel N

ADCCLK

tckpd

tap

tckhw

tcklw

CLAMP

tclpw

N-8

MSB

N-8

LSB

N-7

MSB

N-7

LSB

N-6

MSB

N-6

LSB

[5:0]

[11:6]

Figure 15. Timing Diagram for Figure 14

Triple Channel CCD Application

Figure 16 is a block diagram for pixel-by-pixel applica-
tions with triple channel CCDs. During the optically
shielded section of a pixel, CLAMP must go high to
store the black reference on each capacitor to the input.

The gain and offset is automatically rotated to adjust for
each channel input. The MSBs are available on the
output bus on the falling edge of ADCCLK. The LSBs
are available on the rising edge of ADCCLK.

XRD9827

Rev. 1.20

(CLAMP Enabled)

BLU

GRN

RED

ADCCLK

CLAMP

DATA

PIXEL-BY-PIXEL 3 CHANNEL CCD -- AC Coupled

tdv

RED (N-6)

MSB

N+1 Pixel

CONVERT

RED (N)

CONVERT

GRN (N)

CONVERT

BLU (N)

TRACK

RED (N)

TRACK

GRN (N)

TRACK

RED (N+1)

TRACK

BLU (N)

CONVERT
RED (N+1)

tdv

RED (N-6)

LSB

GRN (N-6)

MSB

GRN (N-6)

LSB

BLU (N-6)

MSB

BLU (N-6)

LSB

CLAMP

tsa

SYNCH

tsypw

tclp=10ns

tap

tclp=10ns

N+1 Pixel

N Pixel

Simultaneous

Sample

trars

ADCCLK

Events

3rd

Simultaneous RED/GRN/BLU Sample Every 3rd CLK.

Convert RED, S/H GRN, S/H BLU.

All

MSB Data Out

LSB Data Out

ADC Track PGA Output

ADC Hold/Convert

CLAMP

Events

Internal Clamp Enabled

Internal RED/GRN/BLU Tracking Enabled

SYNCH

Events

Reset Internal Mux to Red, Output Bus is Tri-stated

Increment Mux Color on Falling Edge of ADCCLK

Table 5.

Figure 18. Timing Diagram for Figure 17

XRD9827

Rev. 1.20

T/H

From CCD RED

Channel

From CCD

GRN Channel

From CCD BLU

Channel

12-Bit ADC

S1 S2 S3

ADCCLK

CLAMP

S4 and S5 open
at this falling
edge

S6 opens, S7
closes at this
rising edge

S7 opens, S8
closes at this
rising edge

S8 Opens, S4,
S5 and S6
close at this
rising edge

Track
GRN

Track
BLU

Track
RED

Convert

RED

Convert

RED

Convert

GRN

Convert

BLU

CCD
Waveform

S8 Opens, S4,
S5 and S6
close at this
rising edge

S9 closes at rising edge and opens
at falling edge of ADCCLK

S1, S2 and S3 close when
CLAMP is high and open
when CLAMP is low

PGA

C EXT R

C EXTG

C EXT B

VCDS = PGAG * [V

- (V

- V

PIX

)]

= PGAG * V

PIX

XRD9827

RT -

PIX

BLK

Figure 19. CDS Timing (Triple Channel)

Mode: 110 00001110

XRD9827

Rev. 1.20

Mode 2. DC Coupled

Typical CCDs have outputs with black references.
Therefore, DC Coupled is not recommended for CCD
applications.

Offset Control DAC

The offset DAC is controlled by 8 bits. The offset range
is 800 mV ranging from -200 mV to +600 mV (when DB5
is set to 0) and -400 mV to +400 mV (when DB5 is set
to 1). Therefore, the resolution of the 8-Bit offset DAC
is 3.14 mV. However, the XRD9827 has +/- 100 mV
reserved for internal offsets. Therefore, the effective
range for adjusting for CIS offsets or black reference is
600 mV. The offset adjustment is used primarily to
correct for the difference between the black level of the
image sensor and the bottom ladder reference voltage
(VRB) of the ADC. By adjusting the black level to
correspond to VRB, the entire range of the ADC can be
used.

If the offset of the CIS output is greater than 500 mV an
external reference can be applied to VDCEXT. The
external reference can be used to adjust for large
offsets only when the internal mode is configured
through the serial port.

Since the offset DAC adjustment is done before the
gain stage, it is gain-dependent. For example, if the
gain needs to be changed between lines (red to blue,
etc.), the offset is calibrated before the signal passes
through the PGA.

PGA (Programmable Gain Amplifier) DAC

The gain of the input waveform is controlled by a 6-Bit
PGA. The PGA is used along with the offset DAC for
the purpose of using the entire range of the ADC. The
PGA has a linear gain from 1 to 10. Figure 20 is a plot
of the transfer curve for the PGA gain.

PGA GAIN TRANSFER CURVE

GAIN 1 - 10

CODE

GAIN

Figure 20. Transfer Curve for the 6-Bit PGA

After the signal is level shifted to correspond with the
bottom ladder reference voltage, the system can be
calibrated such that a white video pixel can represent
the top ladder reference voltage to the ADC. This allows
for a full scale conversion maximizing the resolution of
the ADC.

Analog to Digital Converter

The ADC is a 12-Bit, 10 MSPS analog-to-digital con-
verter for high speed and high accuracy. The ADC uses
a subranging architecture to maintain low power con-
sumption at high conversion rates. The output of the
ADC is on 8-bit databus. The 8-bit databus supports
6x6 or 8x4 output data. ADCCLK samples the input on
its falling edge. After the input is sampled, the MSB is
latched to the output drivers. On the rising edge of the
ADCCLK, the LSB is latched to the output drivers. The
output needs to be demultiplexed with external circuitry
or a digital ASIC. There is an 8 clock cycle latency
(Config 00, 11) or 6 pixel count latency (Config 01, 10)
for the analog-to-digital converter.

The V

and V

reference voltages for the ADC are

generated internally, unless the external V

is se-

lected. In the external V

mode, the V

voltage is set

through the VREF+ pin. This allows the user to select
the dynamic range of the ADC.

XRD9827

Rev. 1.20

Serial Load Control Registers

The serial load registers are controlled by a three wire
serial interface through the bi-directional parallel port to
reduce the pin count of this device. When SYNCH is set
to high, the output bus is tri-stated and the serial
interface is activated. DB7/LD, DB5/SCLK and DB6/
SDATA are the three input signals that control this
process. The DB7/LD signal is set low to initiate the
loading of the internal registers.

There are internal registers that are accessed via an 11-
bit data string. Data is shifted in on the rising edge of
SCLK and loaded to the registers on the rising edge of
LD. The data on pin DB6/SDATA is latched automati-
cally after eleven DB5/SCLKs have been counted. If
eleven clocks are not present on DB5/SCLK before the
DB7/LD signal returns high, no data will be loaded into
the internal registers. If more than 11 clocks are
present on DB5/SCLK, the additional clocks will be
ignored. The data corresponding to the first eleven
DB5/SCLKs will be loaded only.

The first three MSBs choose which internal register will
be selected. The remaining 8 LSBs contain the data
needed for programming the internal register for a
particular configuration.

Power-Up State of the Internal Registers

The control register settings upon initial power-up are
for CIS, DC Coupled configuration (V

is set to internal,

Input DC Reference=AGND and the input to the ADC is
selected through the RED channel). Gain is unity and
Offset is set to zero. The test modes are disabled in the
power-up state.

D B 6 / S D A T A

D B 5 / S C L K

S Y N C H

S 2

S 1

S 0

D 7

D 2

D 1

D 0

D B 7 / L D

tdl

tdz

tsclkw

tds tdh

Figure 21. Write Timing

XRD9827

Rev. 1.20

Note :

These are the control register settings upon initial power-up. The previous register settings are retained
following

a logic power-down initiated by the power down bit except the signal configuration. When

de-selecting the power down bit (D7 = 0, Normal), the signal configuration (D5 and D0) has to be
reprogrammed.

Function
(Register
S2/S1/S0)

Power-up

State

(Note 1)

Red Gain

000000XX

(000)

(MSB)

(LSB)

Red Offset

01000000

(001)

(MSB)

(LSB)

Grn Gain

000000XX

(010)

(MSB)

(LSB)

Grn Offset
(011)

01000000

(MSB)

(LSB)

Blu Gain
(100)

000000XX

(MSB)

(LSB)

Blu Offset
(101)

01000000

(MSB)

(LSB)

Mode

POWER

DIGITAL

INPUT DC

DC/AC

SIGNAL

00000000

(110)

DOWN

RESET

REFERENCE

POLARITY

CONFIGURATION

DCREF

)

0: NORMAL

0: NO RESET

0: INTERNAL

0: DC

0: Non-

00: Single-Channel

DCREF

=AGND)

Inverted

RED input/gain/offset

1:RESET

1: EXTERNAL

1: AC

(CIS)

POWER

(REGISTERS

DCREF

DCEXT

)

1: Inverted

01: Single-Channel

DOWN

ARE RESET TO

(CCD/CIS)

RED input

POWER-UP

RED/GRN/BLU

STATES)

gain/offset cycle

pixel-by-pixel

10: Triple-Channel

RED/GRN/BLU

input/gain/offset cycle

pixel-by-pixel

11: Triple-Channel

RED/GRN/BLU

input/gain/offset cycle

line-by-line

Mode

OUTPUT

OFFSET

INTERNAL CIS

TEST4

TEST3

TEST2

TEST1

00000000

&Test

BUS

DISABLE

DAC

REFERENCE

(111)

CONTROL

RANGE

CIRCUIT

0: 6 MSB +

0:OUTPUTS

0:-200mV to

0:NORMAL

0: TEST4

0: TEST3

0: TEST2

0:NORMAL

6 LSB

ENABLED

+600mV

DISABLED

1: 8 MSB +

1:OUTPUTS

1:-400mV to

1:REFERENCE

1: OUTPUT

1: INPUT

1: TEST1

4 LSB

DISABLED

+400mV

CIRCUIT

OF BUFFER

OF PGA

OF ADC

ENABLED

TIED TO

BLU

VDCEXT

GRN

Control Registers

XRD9827

Rev. 1.20

NOTICE

EXAR Corporation reserves the right to make changes to the products contained in this publication in order to
improve design, performance or reliability. EXAR Corporation assumes no responsibility for the use of any
circuits described herein, conveys no license under any patent or other right, and makes no representation that
the circuits are free of patent infringement. Charts and schedules contained here in are only for illustration
purposes and may vary depending upon a user's specific application. While the information in this publication
has been carefully checked; no responsibility, however, is assumed for in accuracies.

EXAR Corporation does not recommend the use of any of its products in life support applications where the
failure or malfunction of the product can reasonably be expected to cause failure of the life support system or to
significantly affect its safety or effectiveness. Products are not authorized for use in such applications unless
EXAR Corporation receives, in writing, assurances to its satisfaction that: (a) the risk of injury or damage has
been minimized; (b) the user assumes all such risks; (c) potential liability of EXAR Corporation is adequately
protected under the circumstances.

Copyright 2000 EXAR Corporation
Datasheet May 2000
Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited.

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