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ADS-943

5

THERMAL REQUIREMENTS

All DATEL sampling A/D converters are fully characterized and

specified over operating temperature (case) ranges of 0 to

production testing is performed without the use of heat sinks or

forced-air cooling. Thermal impedance figures for each device

are listed in their respective specification tables.

These devices do not normally require heat sinks, however,

standard precautionary design and layout procedures should

be used to ensure devices do not overheat. The ground and

power planes beneath the package, as well as all pcb signal

runs to and from the device, should be as heavy as possible to

help conduct heat away from the package.

Electrically-insulating, thermally-conductive "pads" may be

installed underneath the package. Devices should be soldered

to boards rather than "socketed", and of course, minimal air

flow over the surface can greatly help reduce the package

temperature.

In more severe ambient conditions, the package/junction

temperature of a given device can be reduced dramatically

(typically 35%) by using one of DATEL's HS Series heat sinks.

See Ordering Information for the assigned part number. See

page 1-183 of the DATEL Data Acquisition Components

Catalog for more information on the HS Series. Request

DATEL Application Note AN-8, "Heat Sinks for DIP Data

Converters", or contact DATEL directly, for additional

information.

Figure 4. ADS-943 Timing Diagram

OUTPUT

DATA

Data N Valid

Scale is approximately 20ns per division. Sampling rate = 3MHz.

EOC

Data N-1 Valid

Data N+1 Valid

Invalid

Data

283ns typ.

35ns typ.

130ns

1.

The start convert positive pulse width must be between either 10 and 110nsec or

160 and 300nsec (when sampling at 3MHz) to ensure proper operation. For sampling

rates lower than 3MHz, the start pulse can be wider than 300nsec, however a minimum

pulse width low of 30nsec should be maintained. A 3MHz clock with a 20nsec positive

pulse width is used for all production testing.

2.

Note:

10ns max.

INTERNAL S/H

10ns typ.

Acquisition Time

125ns typ.

208ns typ.

215ns max.

Hold

Conversion Time

120ns min., 130ns typ.,

140ns max.

50ns typ.

30ns typ.

125ns typ.

START

CONVERT

N

N+1

333nsec

20ns typ.