SPT1018 데이터 시트보기 (PDF) - Cadeka Microcircuits LLC.

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SPT1018

8-BIT, HIGH SPEED D/A CONVERTER

Cadeka Microcircuits LLC. 

Figure 4 - CONVert, CONVert Switching Levels

VIDF

0.0 V

VICM MIN

VICM MAX

Figure 5A - Standard Load

-1.3 V

CONV

CONV

OUT-

RS

75 Ω

SPT1018

Video Monitor

75 Ω COAX

RL

75 Ω

OUT +

RS

75 Ω

75 Ω COAX

Inverse

Video

RL

75 Ω

Figure 5B - Test Load

OUT +

OUT -

CL

<5 pF

RL

37.5Ω

Video Out

0 to -1 Volt

external load, such as two other DAC reference inputs. (See

the SPT1019 data sheet).

The circuits shown in figure 6 illustrate how a single SPT1019

may be used as a master reference in a system with multiple

DACs (such as RGB). The other DACs are simply slaved from

the SPT1019’s reference output. The SPT1018s shown are

especially well-suited to be slaved to a SPT1019 for a better

TC tracking from DAC-to-DAC, since they are essentially

SPT1019s without the reference. The SPT1018 is pin-com-

patible with the TDC1018, that does not have an internal

reference. Although either the TDC1018 or the SPT1018 may

be slaved from an SPT1019, the higher performance

SPT1018 and the above mentioned DAC-to-DAC TC track-

ing is the best choice for new designs.

No external reference is required for operation of the

SPT1019, as this function is provided internally. The internal

reference is a bandgap type and is suitable for operation over

extended temperature ranges. The SPT1018 must use an

external reference.

Figure 6 - Typical RGB Graphics System

SPT1019

(Master)

R

SPT1018

(Slave)

G

SPT1018

(Slave)

B

ISet

R1 R2

500 Ω 750 Ω

ISet

Ref Out

Ref+ Ref-

Ref+ Ref-

IRef

500 Ω 750 Ω

ISet

1 kΩ

500 Ω 750 Ω

ISet

1 kΩ

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 convert-

ers track each other over a wide range of operating condi-

tions. 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.

The SPT1019 contains an internal precision bandgap refer-

ence which completely eliminates the need for an external

reference. The reference can supply up to 50 µA to an

Figure 7 - Burn-In Circuit

-5.9 V

(Max 200 mA)

6.5 Ω

6.5 Ω

24 Pin DIP

All Resistors Are 5% 1/4 W cc

Clock = -0.9 to -1.7 V, 100 kHz

-1.2 V

(Max 1.5 mA)

1 kΩ

VEE

Ref-

(Max 50 mA)

Out-

(Max 50 mA)

Out+

100 Ω

100 Ω

-1.3 V

(Max 60 µA)

1 kΩ

Clock

(Max 60 µA)

1 kΩ

CONV

CONV

Ref+

1 kΩ

(Max 1.5 mA)

VCC

SPT1018

8

5/14/97

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