Texas Instruments SN28835FS, SN28835FS-X Datasheet

SN28835

1/2-INCH NTSC TIMER

SOCS023B – FEBRUARY 1991

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

• NTSC-Timing Operation

• Solid-State Reliability

• Color and Monochrome Operation

• Four Selectable-Antiblooming Modes

• Variable-Integration-Time Option

• Surface-Mount Package

• Clamp-Pulse Select Option

• Horizontal and Vertical Resets for External

Synchronization

description

The SN28835 is a monolithic integrated circuit designed to supply timing signals for the Texas Instruments (TI) 8-mm TC242/TC244 color and TC243/TC245 monochrome CCD image sensors. The SN28835 supplies both CCD-drive signals and NTSC-television synchronization signals at standard video rates. It requires a single 5-V supply voltage and a 14.318-MHz crystal-oscillator input. The SN28835 provides the user with several options including multiple antiblooming modes, variable-integration time, external synchronization, and delayed horizontal transfer.

The SN28835 is designed to drive the CCD image sensor through intermediary level-shifting devices such as the TI TMS3473B parallel driver and the SN28846 serial driver. It also supplies sample-and-hold signals for the TI TL1593 3-channel sample-and-hold circuit and multiplex signals for the TI TL1051 video preprocessor. The SN28835 NTSC synchronization-signal outputs include composite sync, composite blank, clamp, subcarrier, subcarrier delayed by 90 degrees, and burst flag.

The SN28835 is supplied in a 44-pin plastic flat package and is characterized for operation from –20°C to 45°C.

This device contains circuits to protect its inputs and outputs against damage due to high static voltages or electrostatic fields. These circuits have been qualified to protect this device against electrostatic discharges (ESD) of up to 2 kV according to MIL-STD-883C, Method 3015; however, precautions should be taken to avoid application of any voltage higher than maximum-rated voltages to these

high-impedance circuits. During storage or handling, the device leads should be shorted together or the device should be placed in conductive foam. In a circuit, unused inputs should always be connected to an appropriated logic voltage level, preferably either VCC or ground. Specific guidelines for handling devices of this type are contained in the publication

Guidelines for Handling Electrostatic-Discharge-Sensitive

(ESDS) Devices and Assemblies

available from Texas Instruments.

TI is a trademark of Texas Instruments Incorporated.

GND MODE PI ABIN GT PS PD S3 S2 S1 T

12 13

1 2 3 4 5 6 7 8 9 10 11

BCP1 BCP2

CP2 CP1

CSYNC

CBLK

SC(90)

ABS0 ABS1

14 15 16 17

GT3/SH2

SH1X2X1

43 42 41 40 3944 38

E/L

VDS

HCR

VCR

GT2

GT1/SH3

VGATE

HGATE

CLK2M

HIGH

GPS

VD2

WHTA

36 35 3437

18 19 20 21 22

FS PACKAGE

(TOP VIEW)

33 32 31 30 29 28 27 26 25 24 23

PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters.

SN28835 1/2-INCH NTSC TIMER

SOCS023B – FEBRUARY 1991

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

functional block diagram

Oscillator

Divide

by 7

14.318 MHz

2.045 MHz

Divide by 4, Phase Shift

Horizontal

Counter

Vertical

Counter

Clock

Generator

Antiblooming

Generator

Serial

Generator

Decoder

27 29 31 28 23

BCP1 BCP2 CP1 CP2 CSYNC CBLK BF VD FI VGATE HGATE WHTA VD2

PD GT PI PS T

S1 S2 S3 SH1 GT3/SH2 GT1/SH3 GT2

24 25 26 36 37 38 39

ABIN

13 15 42 14

GPS

VDS

ABS0 ABS1

10 11

MODE

E/L

32 43

HCR

VCR

SC(90)

CLK2M

2 4

3 5 6

7 16 44 19 20 18 17

The levels on these two terminals determine which of the four antiblooming modes is selected:

ABS1 ABS0 Operation

L L No ABG pulses L H 2-MHz burst of ABG pulses H L 1-MHz burst of ABG pulses H H 1-MHz continuous ABG pulses

SN28835

1/2-INCH NTSC TIMER

SOCS023B – FEBRUARY 1991

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

Terminal Functions

TERMINAL

NAME NO.

I/O

DESCRIPTION

ABIN 30 O Antiblooming in

ABS0 10 I

ABS1 11 I

BCP1 1 O Optical black clamp BCP2 2 O Optical black clamp BF 7 O Burst flag CBLK 6 O Composite blank CLK2M 21 O 2-MHz clock CP1 4 O Clamp CP2 3 O Clamp CSYNC 5 O Composite sync

E/L 43 I

Delay select for S1, S2, S3. When E/L is high, the three serial-transfer pulses occur early relative to the sample-and-hold pulses SH1, SH2, and SH3. When E/L

is low, the three serial-transfer pulses occur

late relative to the sample-and-hold pulses.

FI 44 O Field index GND 33 Ground GP 15 I Exposure control: GP gates the PS and PI outputs (see the description of GPS)

GPS 13 I

When GPS is high, the timer operates in the normal-integration-time mode (t

int

= 16.67 ms) and VD is connected internally to GP . To operate the imager in the variable-integration-time mode, GPS must be held low and a user-defined logic circuit must be inserted between VD and GP to vary the integration time (see Figure 1).

GT 29 O TMS3473B parallel-driver MIDSEL input switch GT1/SH3 38 O

GT1/SH3 is a logic signal for both Y gate 1 of the TL1051 video preprocessor and sample-and-hold channel 3 of the TL1593 3-channel sample-and-hold circuit.

GT2 39 O Y gate 2 for the TL1051 video preprocessor GT3/SH2 37 O

GT3/SH2 is a logic signal for both Y gate 3 and sample-and-hold channel 2 of the TL1051 video preprocessor.

HCR 41 I Horizontal-counter reset HGATE 20 O Decoded H count signal. HGATE is a test point and is not used in normal operation. HIGH 12 I Not used (tie high)

MODE 32 I

TC243/TC245 CCD select. When MODE is low, the TC244/245 CCD imager is selected; when MODE is high, the TC242/243 is selected (see the appropriate data sheets for imager differences).

PD 27 O Power down. A low-logic level on PD causes the device to enter a low power-consumption mode. PI 31 O Parallel-image-area gate clock PS 28 O Parallel-storage-area gate clock

SB 14 I

Standby-mode select. When SB is high, normal operation is selected; when SB is low, the power-down mode is selected.

SC 8 O Subcarrier SC(90) 9 O Subcarrier phase shifted by 90 degrees SH1 36 O Sample and hold 1

SN28835 1/2-INCH NTSC TIMER

SOCS023B – FEBRUARY 1991

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

Terminal Functions (Continued)

TERMINAL

NAME NO.

I/O

DESCRIPTION

S1 24 O Serial clock 1 S2 25 O Serial clock 2 S3 26 O Serial clock 3 T 23 O Transfer-gate clock V

22 DC power VCR 40 I Vertical-counter reset VD 16 O Vertical drive

VDS 42 I

Vertical-dump speed. When VDS is high, the vertical-dump frequency is 3.58MHz; when VDS is low,

the vertical-dump frequency is 2 MHz. VD2 17 O Real-display-area signal. VD2 is a test point and is not used in normal operation. VGATE 19 O Decoded V count signal. VGATE is a test point and is not used in normal operation. WHTA 18 O WHTA is a test point and is not used in normal operation. X1 34 X2 35

Crystal oscillator (see Figure 2)

12 3

int

Flush Pulses Transfer Pulse

Figure 1. GP Flush and Transfer Pulses

SN28835

1/2-INCH NTSC TIMER

SOCS023B – FEBRUARY 1991

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

variable-integration-time mode

In addition to the normal TV mode of operation, the SN28835 timing generator offers an optional variable-integration mode for use with the TC244 and TC245 CCD area-array image sensors. The variable-integration mode is selected by applying a low-logic level to GPS. This low-logic level disables the vertical-drive (VD) signal from controlling, internal to the timer, the image-area and storage-area parallel transfer signal (GP).

Prior to the start of a new integration period, the charge that has accumulated in the image area must be transferred out. To flush this previous signal or dark-current charge from the image area, GP is pulsed low two times. Each low pulse generates 256 image-area and storage-area gate and transfer signals that shift the unwanted charge into the clearing drain. This clearing function should be performed during the high time of the VD signal (see Figure 3 through Figure 12).

The new integration period continues as long as GP remains high. GPS must be held at a low-logic level to prevent VD from controlling GP internally . The integration ceases and the readout occurs when VD and GP are pulsed low simultaneously; this is accomplished by taking GPS to a high-logic level. The readout timing is dependent on the vertical-drive pulse; this means that the total-integration time is a multiple of 1/60 of a second plus the time interval between the last GP low pulse and the next VD low pulse. The image readout occurs within the normal 1/60-second readout interval. If the integration time is less than 1/60 of a second, normal output operation occurs; if the integration time is greater than 1/60 of a second, a frame buffer may be required to capture the image.

Integration times greater than 1/60 of a second result in image degradation at temperatures greater than 25°C due to dark-current generation. The degradation is seen as a decrease in dynamic range (contrast) and an increase in noise. It is recommended that the image sensor be cooled for long-exposure operation. The dark-current generation is reduced by a factor of two for each 7°C temperature decrease. The sensor operates at –30°C. Cooling can be accomplished by using a thermoelectric or Peltier cooler attached to the image sensor . Condensation on the header must be prevented by isolating the cooled sensor from moist air. V acuum isolation is preferred; however, the continual flushing of dry nitrogen across the header can also prevent condensation.

X1 X2

34 35

C1 ≈ 40 pF C2 ≈ 40 pF

SN28835

NOTE: The SN28835 is designed for use with a

crystal oscillator. The X1 and X2 terminals should not connect directly to external driver outputs.

Figure 2. Connection of an External Crystal Oscillator to the SN28835

SN28835 1/2-INCH NTSC TIMER

SOCS023B – FEBRUARY 1991

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

absolute maximum ratings over operating free-air temperature range (unless otherwise noted)

†

Supply voltage range, V

(see Note 1) –0.3 V to 7 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Input voltage range, V

–0.3 V to VCC + 0.3 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Output voltage range, V

–0.3 V to VCC + 0.3 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Continuous total power dissipation at (or below) T

= 25°C 300 mW. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Operating free-air temperature range, T

–20°C to 45°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Storage temperature range, T

STG

–55°C to 125°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds 260°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

†

Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

NOTE 1: All voltage values are with respect to GND.

recommended operating conditions

MIN NOM MAX UNIT

Supply voltage, V

4.5 5 5.5 V

High-level input voltage, V

VCC x 0.7 V

Low-level input voltage, V

IL 0.8

V Operating frequency 14.318 MHz Power-up time 300 µs Operating free-air temperature, T

–20 45 °C

electrical characteristics over recommended ranges of supply voltage and operating free-air temperature (unless otherwise noted)

‡

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

GT3/SH2 and GT1/SH3 VCC = 4.5 V, IOH = –4 mA 3.5

All other outputs VCC = 4.5 V, IOH = –2 mA 3.5

GT3/SH2 and GT1/SH3 VCC = 4.5 V, IOL = 4 mA 0.5

All other outputs VCC = 4.5 V, IOL = 2 mA 0.5

VIH = 5 V 1 µA

VIL = 0 –30 –200 –500 µA

CC(AV)

Average supply current 10 30 mA

CC(S)

Standby supply current 1 mA

‡

The SB input is a Schmitt-trigger input with 0.1-V to 1-V hysteresis.

All inputs except X1 have pullup-current sources.

switching characteristics over recommended ranges of supply voltage and operating free-air temperature

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

SC, SC(90) 3.579545

clock

Frequenc

S1, S2, S3, SH1, GT2, GT1/SH3, GT3/SH2

4.772727

SC, SC(90)

= 50

140

twPulse duration

S1, S2, S3, SH1, GT2, GT1/SH3, GT3/SH2 70

GT1SH3 and GT3SH2 10

trRise time

All other outputs

GT1SH3 and GT3SH2

= 50

tfFall time

All other outputs 50

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