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ADS-927

5

THERMAL REQUIREMENTS

All DATEL sampling A/D converters are fully characterized and

specified over operating temperature (case) ranges of

0 to +70°C and –55 to +125°C. All room-temperature

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-927 Timing Diagram

2. The ADS-927 is a pulse-triggered device. Its internal operations

are triggered by both the rising and falling edges of the start

convert pulse. When sampling at 1MHz, the start pulse must be

between 175 and 225nsec wide. For lower sampling rates, wider

start pulses may be used, however, a minimum pulse width low of

50nsec must be maintained.

START

CONVERT

OUTPUT

DATA

INTERNAL S/H

N

N + 1

Data (N – 1) Valid

Acquisition Time

10ns

typ.

Data N Valid (850ns min.)

EOC

Conversion Time

Invalid

Data

150ns max.

10ns typ.

390ns ±55ns

35ns max.

Hold

200ns

±25ns

610ns typ.

480ns ±20ns

70ns ±10ns