Datasheet SPT5140SIN Datasheet (SPT)

SPT

SIGNAL PROCESSING TECHNOLOGIES

SPT5140

8-BIT, ULTRAHIGH-SPEED D/A CONVERTER

FEATURES

• 400 MWPS nominal conversion rate

• RS-343-A compatible

• Complete video controls: Sync, Blank, Bright
and Reference White (Force High)

• 10 KH, 100K ECL compatible

• Single power supply

• Registered data and video controls

• Differential current outputs

• Stable on-chip bandgap reference

• 50 and 75 ohm output drive

• ESD-protected data and control inputs

GENERAL DESCRIPTION

The SPT5140 is a monolithic 8-bit digital-to-analog con­verter capable of accepting video data at 400 MWPS.
Complete with video controls — Sync, Blank, Reference
White (Force High), Bright — the SPT5140 directly drives
doubly-terminated 50 or 75 ohm loads to standard com­posite video levels. Standard set-up level is 7.5 IRE. The

BLOCK DIAGRAM

APPLICATIONS

• Raster graphics

• High-resolution color or monochrome displays
to 2k x 2k pixels

• Medical electronics: CAT, PET, MR imaging displays

• CAD/CAE workstations

• Solids modeling

• General-purpose high-speed D/A conversion

• Digital synthesizers

• Automated test equipment

• Digital transmitters/modulators

SPT5140 includes an internal precision bandgap refer­ence which can drive two other SPT5140s in an RGB
graphics system.

The SPT5140 is available in a 24-lead PDIP package in
the industrial temperature range of –25 °C to +85 °C.
Contact the factory for military temperature and /883
versions.

Video Controls In

Video Data In

Video Data In

Feedthrough

Convert

I

Set

Ref In

Ref Out

Sync, Blank, Bright, Ref – White

D0–D3

4 to 15

D4–D7

(MSBs)

4

Decode

4

4

2

Ref

Buffer

Register

4

4

Bandgap

Reference

Out +

Output

Current

Switches

Out –

Signal Processing Technologies, Inc.

4755 Forge Road, Colorado Springs, Colorado 80907, USA

Phone: [phone] FAX: [phone] Website: http://www.spt.com E-Mail: [e-mail]

ABSOLUTE MAXIMUM RATINGS (Beyond which damage may occur)1 25 °C

Supply Voltages

VEE (measured to VCC) .......................... –7.0 to 0.5 V

Temperature

Operating,ambient............................... –25 to +85 °C

junction ....................................... + 175 °C

Input Voltages

CONV, Data, and Controls...................... VEE to 0.5 V

Lead, soldering (10 seconds) ...................... + 300 °C

Storage ............................................. –60 to + 150 °C

(measured to VCC)

Ref+ (measured to VCC) ......................... VEE to 0.5 V

Ref– (measured to VCC).......................... VEE to 0.5 V

Note 1: Operation at any Absolute Maximum Rating is not implied. See Electrical Specifications for proper nominal applied

conditions in typical applications.

ELECTRICAL SPECIFICATIONS

VCC = ground, VEE = –5.2 V ±0.3 V, TA = T

PARAMETERS CONDITIONS LEVEL MIN TYP MAX UNITS
DC Electrical Characteristics

Integral Linearity Error 1.0 mA<I

Differential Linearity Error 1.0 mA<I

Gain Error VI –6.5 +6.5 % FS
Gain Error Tempco V 150 PPM/°C
Bandgap Tempco V 100 PPM/°C
Input Capacitance, I
Compliance Voltage, + Output VI –1.2 1.5 V
Compliance Voltage, – Output VI –1.2 1.5 V
Equivalent Output Resistance VI 20 kΩ
Output Capacitance V 9 pF
Maximum Current, + Output IV 45 mA
Maximum Current, – Output IV 45 mA
Output Offset Current VI 0.05 0.5 LSB
Input Voltage, Logic High VI –1.0 V
Input Voltage, Logic Low VI –1.5 V
Convert Voltage, IV –0.5 –2.5 V

Common Mode Range (V
Convert Voltage, Differential (V
Input Current, Logic Low, VI 35 120 µA

Data and Controls
Input Current, Logic High, VI 40 120 µA

Data and Controls
Input Current, Convert VI 2 60 µA
Reference Voltage

Measured to V
Reference Output Current VI –50 µA
Input Capacitance, V 3 pF

Data and Controls
Power Supply Sensitivity VI –120 +20 +120 µA/V
Supply Current VI 155 220 mA

, Ref Out V 5 pF

Set

)

ICM

) IV 0.4 1.2 V

IDF

CC

to T

MIN

TEST TEST SPT5140

, CC = 0 pF, I

MAX

<1.3 mA VI –0.37 +0.37 % FS

Set

<1.3 mA VI –0.2 +0.2 % FS

Set

= 1.105 mA, unless otherwise specified.

Set

–0.95 +0.95 LSB

–0.5 +0.5 LSB

VI –1.3 –1.2 –1.0 V

SPT

SPT5140

2 3/28/00

ELECTRICAL SPECIFICATIONS

VCC = ground, VEE = –5.2 V ±0.3 V, TA = T

PARAMETERS CONDITIONS LEVEL MIN TYP MAX UNITS
Dynamic Characteristics (RL = 37.5 ohms, CL = 5 pF, TA = +25 °C, I

Maximum Conversion Rate IV 385 400 MWPS
Rise Time 10% to 90% G.S. IV 900 ps
Rise Time 10% to 90% G.S. IV 600 ps

Current Settling Time, Clocked To 0.2% G.S. V 4 ns

Mode (t

)

SI

Current Settling Time, Clocked To 0.2% G.S. V 3 ns

Mode (t

)R

SI

Clock to Output Delay, Clocked IV 2.2 4 ns

Mode (t

) T

DSC

Part-to-Part Clock to Output Delay

Skew, Clocked Mode T
Data to Output Delay, IV 3.2 6 ns

Transparent Mode (t

) T

DST

Glitch Energy Area = 1/2 VT V 4 pV-s
Convert Pulse Width (t

PWH

, t

) IV 1.3 ns

PWL

Reference Bandwidth, –3 dB V 1.25 MHz
Set-up Time, Data and Controls (tS) IV 1.0 ns
Hold Time, Data and Controls (tH) IV 0.5 ns
Slew Rate 20% to 80% G.S. V 700 V/µS
Clock Feedthrough IV –48 dB

MIN

to T

, CC = 0 pF, I

MAX

Set

TEST TEST

Set

RL = 25 ohms

= 25 Ω

L

= T

A

A

A

= T

= T

MIN

MIN

MIN

to T

to T

to T

MAX

MAX

MAX

IV 4.5 ns

IV 1.5 ns

IV 6 ns

= 1.105 mA, unless otherwise specified.

= 1.105 mA)

TEST LEVEL CODES

All electrical characteristics are subject
to the following conditions:

All parameters having min/max specifi­cations are guaranteed. The Test Level
column indicates the specific device
testing actually performed during pro­duction and Quality Assurance inspec­tion. Any blank section in the data
column indicates that the specification
is not tested at the specified condition.

TEST LEVEL TEST PROCEDURE

I 100% production tested at the specified temperature.

II 100% production tested at TA = +25 °C, and sample tested at the

specified temperatures.
III QA sample tested only at the specified temperatures.
IV Parameter is guaranteed (but not tested) by design and characteriza-

tion data.

V Parameter is a typical value for information purposes only.

VI 100% production tested at T

specified temperature range.

= +25 °C. Parameter is guaranteed over

A

SPT

SPT5140

3 3/28/00

Figure 1 – Functional Diagram

D0–D7

Composite

Video Controls

CONV
CONV

Feedthrough

8

4

2

V

EE

V

CC

Decoding

Logic

APPLICATION INFORMATION

The SPT5140 is a high-speed video digital-to-analog
converter capable of up to 400 MWPS conversion rates.
This makes the devices suitable for driving 2048 X 2048
pixel displays at update rates of 60 to 90 Hz.

In addition, the SPT5140 includes an internal bandgap
reference which may be used to drive two other
SPT5140s if desired.

The SPT5140 has 10KH and 100K ECL logic level com­patible video control and data inputs. The complementary
analog output currents produced by the devices are pro­portional to the product of the digital control and data
inputs in conjunction with the analog reference current.
The SPT5140 is segmented so that the four MSBs of the
input data are separated into a parallel “thermometer”
code. From here, fifteen current sinks, which are identi­cal, are driven to fabricate sixteen coarse output levels.
The remaining four LSBs drive four binary weighted
current switches.

MSB currents are then summed with the LSBs that pro­vide a one-sixteenth of full-scale contribution to provide
the 256 distinct analog output levels.

The video control inputs drive weighted current sinks
which are added to the output current to produce com­posite video output levels. These controls — Sync, Blank,
Reference White (Force High) and Bright — are needed
in video applications.

Another feature that similar video D/A converters do not
have is the Feedthrough Control. This pin allows regis­tered or unregistered operation of the video control and

Data

Registers

Bandgap

Reference

Ref Out

Current

Sources

and

Switches

Current

Source

Biasing

Amp

+–

Ref In

I

Set

Out +
Out –

data inputs. In the registered mode, the composite func­tions are latched to the pixel data to prevent screen-edge
distortions generally found on unregistered video DACs.

TYPICAL INTERFACE CIRCUIT

GENERAL

A typical interface circuit using the SPT5140 in a color
raster application is shown in figure 2. The SPT5140
requires few external components and is extremely easy
to use. The very high operating speeds of the SPT5140
require good circuit layout, decoupling of supplies, and
proper design of transmission lines. The following consid­erations should be noted to achieve best performance.

INPUT CONSIDERATIONS

Video input data and controls may be directly connected
to the SPT5140. Note that all ECL inputs are terminated
as closely to the device as possible to reduce ringing,
crosstalk and reflections. A convenient and commonly
used microstrip impedance is about 130 ohms, which is
easily terminated using a 330 ohm resistor to VEE and a
220 ohm resistor to ground. This arrangement gives a
Thevenin equivalent termination of 130 ohms to –2 volts
without the need for a –2 volt supply. Standard SIP
(Single Inline Package) 220/330 resistor networks are
available for this purpose.

It is recommended that stripline or microstrip techniques
be used for all ECL interface. Printed circuit wiring
of known impedance over a solid ground plane is
recommended.

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SPT5140

4 3/28/00

Figure 2 – Typical Interface Circuit

FT

Video

Control

Inputs

FH
Blank
BRT
Sync

Video Monitor

4

4

Out–

R

3

50/75 Ω

50/75 Ω COAX

R

4

50/75 Ω

R

1

1 kΩ

LM113/313

–5.2 V

Optional External

Reference

D0 (LSB)
D1
D2

V+

V–

.01 µF

FB

D3

D4
D5
D6
D7 (MSB)

CONV

CONV

I

)(

*

Set

Ref In

Jumper J1

Remove J1 For

External Reference

4 to 15

Decode

Video

Data

Inputs

Clock

R

2

1 kΩ

I

Set

1kΩ

2 kΩ

An external reference can be used or the reference from

*

Ref Out can drive three SPT5140s.

Ref

Buffer

Register

Bandgap

Reference

V

CC

.01 µF

10 µF

NOTES:

Output Current Switches

7.

V

EE

8.

9.

10.

11.

–5.2 V

12.

Out+

V– = –1.2 V (typical) for LM113 or V

1.
V+ = –1.2 V

2.
I

Set

3.
R

4.

L

V

5.

OUT

V

6.

Sync

=

α

T(R

= R3 / / R

[

=

K

= (K x I

V+

; typ = 1.105 mA

)

1+R2

4

255–Digital Input Code

255

[

K

x I

x RL(bright)

1

Set

x RL) + (K2 x I

Set

xI

Set

Set

]

x RL)
K = 15.8069
K

= 1.7617

1

K

= 10.0392

2

FB = Ferrite bead, Fair-rite pin 217430011
or equivalent.

All reference resistors 1/8 W 1% metal
film, power supply decoupling 50 V
ceramic disc

= ECL Terminationx

= V

= AGND

CC

See figure 9 for detail on Ref Buffer.

= DGND (digital input drivers).

]

BG

RL +

OUTPUT CONSIDERATIONS

The analog outputs are designed to directly drive a dou­bly terminated 50 or 75 ohm load transmission system as
shown. The source impedances of the SPT5140 outputs
are high impedance current sinks. The load impedance
(RL) must be 25 or 37.5 ohms to attain standard RS-343­A video levels. Any deviation from this impedance will
affect the resulting video output levels proportionally. As
with the data interface, it is important that the analog
transmission lines have matched impedance throughout,
including connectors and transitions between printed
wiring and coaxial cable. The combination of matched
source termination resistor RS and load terminator R
minimizes reflections of both forward and reverse travel­ing waves in the analog transmission system. The return
path for analog output current is VCC, which is connected
to the source termination resistor RS.

SPT

POWER CONSIDERATIONS

The SPT5140 operates from a single –5.2 V standard
supply . Proper bypassing of the supplies will augment the
SPT5140’s inherent supply noise rejection characteris­tics. As shown in figure 2, each supply pin should be by­passed as close to the device as possible with 0.01 µF
and 10 µF capacitors.

The SPT5140 has two analog (VEE) power supply pins.
Both supply pins should be properly bypassed as men­tioned previously. This device also has two analog (VCC)
ground pins. Both ground pins should be tied to the
analog ground plane. Power and ground pins must be

L

connected in all applications. If a +5 V power source is
required, the ground pins (VCC) become the positive sup­ply pins while the supply pins (VEE) become the ground
pins. The relative polarities of the other input and output
voltages must be maintained.

5 3/28/00

SPT5140

REFERENCE CONSIDERATIONS

The SPT5140 has two reference inputs (Ref In and I

Set

and one reference output (Ref Out). The input pins are
connected to the inverting and noninverting inputs of an
internal amplifier that serves as a reference buffer.

The output of the buffer amplifier is the reference for the
current sinks. The amplifier feedback loop is connected
around one of the current sinks to achieve better accu­racy. (See figure 9.)

Since the analog output currents are proportional to the
digital input data and the reference current (I

), the full-

Set

scale output may be adjusted by varying the reference
current. I
SPT5140. A method and equations to set I

is controlled through the (I

Set

input on the

Set)

are shown

Set

in figure 2. The SPT5140 can use an external negative
voltage reference. The external reference must be stable
to achieve a satisfactory output and the Ref In should be
driven through a resistor to minimize offsets caused by
bias current. The value for I

can be varied with the 500

Set

to 1k Ω trimmer to change the full-scale output. A double
50 ohm load (25 ohm) can be driven if I

is increased

Set

by 50% above for doubly-terminated 75 ohm video
applications.

DATA INPUTS AND VIDEO CONTROLS

)

The SPT5140 has standard single-ended data inputs.
The inputs are registered to produce the lowest differen­tial data propagation delay (skew) to minimize glitching.
There are also four video control inputs to generate com­posite video outputs. These are Sync, Blank, Bright and
Reference White or Force High. Also provided is the
Feedthrough control mentioned earlier. The controls and
data inputs are all 10 KH and 100K ECL compatible. In
addition, all have internal pulldown resistors to leave
them at a logic low, so the pins are inactive when not
used. This is useful if the devices are applied as standard
DACs without the need for video controls or if less than
eight bits are used.

The SPT5140 is usually configured in the synchronous
mode. In this mode, the controls and data are synchro­nized to prevent pixel dropout. This reduces screen-edge
distortions and provides the lowest output noise while
maintaining the highest conversion rate. By leaving the
Feedthrough (FT) control open (low), each rising edge of
the convert (CONV) clock latches decoded data and con­trol values into a D-type internal register. The registered
data is then converted into the appropriate analog output

Figure 3 – Timing Diagram

CONV
–1.3 V
CONV

–1.3 V

OUT –

OUT +

t

S

t

PWH

Data Control

Inputs

t

DST

t

t

DSC

H

t

PWL

1/2 LSB

1/2 LSB

t

SI

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SPT5140

6 3/28/00

Table I – Video Control Operation (Output values for setup = 10 IRE and 75 ohm standard load)

Ref Data

Sync Blank White Bright Input Out – (mA) Out – (V) Out – (IRE) Description

1XXXX28.57 –1.071 –40 Sync Level
0 1 X X X 20.83 –0.781 0 Blank Level
0011X0.00 0.000 110 Enhanced High Level
0010X1.95 –0.073 100 Normal High Level

0000000... 19.40 –0.728 7.5 Normal Low Level

0000111... 1.95 –0.073 100 Normal High Level

0001000... 17.44 –0.654 17.5 Enhanced Low Level

0001111... 0.00 0.000 110 Enhanced High Level

by the switched current sinks. When FT is tied high, the
control inputs and data are not registered. The analog
output asynchronously tracks the input data and video
controls. Feedthrough itself is asynchronous and usually
used as a DC control.

The controls and data have to be present at the input pins
for a set-up time of tS before, and a hold time of tH after,
the rising edge of the clock (CONV) in order to be syn­chronously registered. The set-up and hold times are not
important in the asynchronous mode. The minimum
pulse widths high (t

) and low (t

PWH

) as well as settling

PWL

time become the limiting factors. (See figure 3.)
The video controls produce the output levels needed for

horizontal blanking, frame synchronization, etc., to be
compatible with video system standards as described in

Figure 4 – Video Output Waveform for Standard Load

IRE

110

100

0 mV

–73 mV

Bright

Normal High (White)

RS-343-A. Table I shows the video control effects on the
analog output. Internal logic governs Blank, Sync and
Force High so that they override the data inputs as
needed in video applications. Sync overrides both the
data and other controls to produce full negative video
output (figure 4).

Reference White video level output is provided by Force
High, which drives the internal digital data to full-scale
output or 100 IRE units. Bright gives an additional 10% of
full-scale value to the output level. This function can be
used in graphic displays for highlighting menus, cursors
or warning messages. Again, if the devices are used in
non-video applications, the video controls can be left
open.

SPT

7.5
0

–40

–728 mV
–781 mV

–1071 mV

256 Gray Levels

Normal Low (Black)

Blank

Sync

Video

SPT5140

7 3/28/00

Figure 5 – CONVert, CONVert Switching Levels

V

IDF

0.0 V
V

ICM MIN

–1.3 V

Figure 6A – Standard Load

OUT –

R

S

75 Ω

SPT5140

75 Ω COAX

Video Monitor

R

L

75 Ω

CONV

V

ICM MAX

CONV

CONVERT CLOCK

For best performance, the clock should be ECL driven,
differentially, by utilizing CONV and

CONV

(figure 5). By
driving the clock this way, clock noise and power supply/
output intermodulation will be minimized. The rising edge
of the clock synchronizes the data and control inputs to
the SPT5140. Since the actual switching threshold of
CONV is determined by
single-ended by connecting a bias voltage to

CONV

, the clock can be driven

CONV

. The

switching threshold of CONV is set by this bias voltage.

ANALOG OUTPUTS

The SPT5140 has two analog outputs that are high im­pedance, complementary current sinks. The outputs vary
in proportion to the input data, controls and reference cur­rent values so that the full-scale output can be changed
by setting I

as mentioned earlier.

Set

In video applications, the outputs can drive a doubly ter­minated 50 or 75 ohm load to standard video levels. In
the standard configuration of figure 6, the output voltage
is the product of the output current and load impedance
and is between 0 and –1.07 V . The Out– output (figure 4)
will provide a video output waveform with the Sync pulse
bottom at the –1.07 V level. The Out+ is inverted with
Sync up.

OUT +

R

S

75 Ω

Figure 6B – Test Load

OUT +
OUT –

C

<5 pF

Figure 7 – Burn-In Circuit

–5.9 V

(Max 200 mA)

6.5 Ω

V

EE

–1.2 V

(Max 1.5 mA)

1 kΩ

Ref In

75 Ω COAX

L

6.5 Ω

R

L

37.5 Ω

Out–

Out+

24-Pin DIP

(Max 50 mA)

(Max 50 mA)

100 Ω

All Resistors Are 5% 1/4 W cc

Clock = –0.9 to –1.7 V, 100 kHz

R

L

75 Ω

Video Out
0 to –1 Volt

Inverse
Video

100 Ω

SPT

1 kΩ

I

Set

(Max 1.5 mA)

V

CC

–1.3 V

(Max 60 µA)

Clock

(Max 60 µA)

1 kΩ

CONV

CONV

1 kΩ

SPT5140

8 3/28/00

Figure 8 – Typical RGB Graphics System

R

1

500 Ω

I

Set

R

750 Ω

I

Set

2

Ref In

SPT5140

(Master)

Ref Out

I

Ref

R

750 Ω500 Ω 750 Ω500 Ω

I

Set

TYPICAL RGB GRAPHICS SYSTEM

In an RGB graphics system, the color displayed is deter­mined by the combined intensities of the red, green and
blue (RGB) D/A converter outputs. A change in gain or
offset in any of the RGB outputs will affect the apparent
hue displayed on the CRT screen.

Thus, it is very important that the outputs of the D/A con­verters track each other over a wide range of operating
conditions. Since the D/A output is proportional to the
product of the reference and digital input code, a com­mon reference should be used to drive all three D/As in
an RGB system to minimize RGB DAC-to-DAC mismatch
and improve TC tracking.

SPT5140

(Slave)

I

Set

1kΩ

Ref In

I

Set

SPT5140

(Slave)

I

Set

1 kΩ

B

Ref In

G

The SPT5140 contains an internal precision bandgap
reference which completely eliminates the need for an
external reference. The reference can supply up to 50 µA
to an external load, such as two other DAC reference
inputs.

The circuits shown in figure 8 illustrate how a single
SPT5140 may be used as a master reference in a system
with multiple DACs (such as RGB). The other DACs are
simply slaved from the SPT5140’s reference output.

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SPT5140

9 3/28/00

Figure 9 – DAC Output Circuit

Current
Sink #1

Reference

Current

I

SEG

I

Set

Ref In

Reference

Amplifier

+

–

Figure 10 – Equivalent Input Circuits – Data, Clock, Controls and Reference

Current

Sink #N

I

SEG

OUT +

OUT –

V

EE

CONV

CONV

I

Ref In

I

Reference

Segment

Switch

Bias

Set

Data and

Controls

80 kΩ

V

V

EE

V

CC

EE

V

SPT

I

Bias

I

Bias

I

Bias

V

EE

SPT5140

10 3/28/00

24

1

PACKAGE OUTLINE

24-Lead PDIP

INCHES MILLIMETERS

SYMBOL MIN MAX MIN MAX

K

I

J

A
B
C
D
E

F
G
H

I
J
K

0.125

0.015

0.100 typ

0.055

0.008

0.150 typ

0.600

0.530

1.245

0.070

H

0.190

0.135

0.022

0.065

0.012

0.625

0.550

1.255

0.080

3.18

0.38

2.54 typ

1.40

0.20

3.81 typ

15.24

13.46

31.62

1.78

4.83

3.43

0.56

1.65

0.30

15.88

13.97

31.88

2.03

A

B

C

D

E

F

G

SPT

SPT5140

11 3/28/00

PIN ASSIGNMENTS PIN FUNCTIONS

Name Function

D3

1

24

D4

D3 Data Bit 3

D2
D1
D0

V

EE

CONV
CONV

FT

V

CC

FH

Blank

BRT

10

11

12

2

3

4

5

6

7

8

9

23

22

21

20

19

18

17

16

15

D5
D6
D7

V

EE

Out +
Out –

V

CC

I

Set

Ref In

D2 Data Bit 2
D1 Data Bit 1
D0 Data Bit 0 (LSB)
V

EE

Negative Supply

CONV Convert Clock Input

CONV

Convert Clock Input Complement
FT Register Feedthrough Control
V

CC

Positive Supply
FH Data Force High Control
Blank Video Blank Input

14

Ref Out

BRT Video Bright Input

13

Sync

Sync Video Sync Input
Ref Out Reference Output
Ref In Reference Input
I

Set

Reference Current
Out – Output Current Negative
Out + Output Current Positive
D7 Data Bit 7 (MSB)
D6 Data Bit 6
D5 Data Bit 5
D4 Data Bit 4

ORDERING INFORMATION

PART NUMBER TEMPERATURE RANGE PACKAGE

SPT5140SIN –25 to +85 °C 24L PDIP

Signal Processing Technologies, Inc. reserves the right to change products and specifications without notice. Permission is hereby
expressly granted to copy this literature for informational purposes only. Copying this material for any other use is strictly prohibited.

WARNING – LIFE SUPPORT APPLICATIONS POLICY – SPT products should not be used within Life Support Systems without the
specific written consent of SPT. A Life Support System is a product or system intended to support or sustain life which, if it fails, can
be reasonably expected to result in significant personal injury or death.

Signal Processing Technologies believes that ultrasonic cleaning of its products may damage the wire bonding, leading to device
failure. It is therefore not recommended, and exposure of a device to such a process will void the product warranty.

SPT

SPT5140

12 3/28/00