ADS5522IPAP datasheet(27/32 Pages) TI

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SERIAL PROGRAMMING INTERFACE

Assembly Process

PowerPAD PACKAGE

ADS5522

SBAS320C – MAY 2004 – REVISED FEBRUARY 2007

The PowerPAD package is designed so that the lead

frame die pad (or thermal pad) is exposed on the

The

ADS5522

has

internal

registers

for

the

bottom of the IC. This provides a low thermal

programming of some of the modes described in the

resistance path between the die and the exterior of

previous sections. The registers should be reset after

the package. The thermal pad on the bottom of the

power-up by applying a 2

µs (minimum) high pulse

IC can then be soldered directly to the printed circuit

on RESET (pin 35); this also resets the entire ADC

board (PCB), using the PCB as a heatsink.

and sets the data outputs to low. This pin has a

200-k

Ω internal pullup resistor to AV

DD.

The

programming is done through a three-wire interface.

1. Prepare

the

PCB

top-side

etch

pattern

Table 2 shows the different modes and the bit values

including etch for the leads as well as the

to be written to the register to enable them.

thermal pad as illustrated in the Mechanical

Data section. The recommended thermal pad

Note that some of these modes may modify the

dimension is 8 mm x 8 mm.

standard operation of the device and possibly vary

2. Place a 5-by-5 array of thermal vias in the

the performance with respect to the typical data

thermal pad area. These holes should be 13

shown in this data sheet.

mils in diameter. The small size prevents

Applying a RESET signal is absolutely essential to

wicking of the solder through the holes.

set the internal registers to their default states for

3. It is recommended to place a small number of

normal operation. If the hardware RESET function is

25 mil diameter holes under the package, but

not used in the system, the RESET pin must be tied

outside the thermal pad area to provide an

to ground and it is necessary to write the default

additional heat path.

values to the internal registers through the serial

4. Connect all holes (both those inside and

programming interface. The registers must be written

outside the thermal pad area) to an internal

in the following order.

copper plane (such as a ground plane).

Write 9000h (Address 9, Data 000)

5. Do not use the typical web or spoke via

Write A000h (Address A, Data 000)

connection

pattern

when

connecting

the

Write B000h (Address B, Data 000)

thermal vias to the ground plane. The spoke

Write C000h (Address C, Data 000)

pattern increases the thermal resistance to the

Write D000h (Address D, Data 000)

ground plane.

Write E000h (Address E, Data 804)

6. The

top-side

solder

mask

should

leave

exposed the terminals of the package and the

Write 0000h (Address 0, Data 000)

thermal pad area.

Write 1000h (Address 1, Data 000)

7. Cover the entire bottom side of the PowerPAD

Write F000h (Address F, Data 000)

vias to prevent solder wicking.

NOTE:

8. Apply solder paste to the exposed thermal

This procedure is only required if a RESET pulse

pad area and all of the package terminals.

is not provided to the device.

For

detailed

information

regarding

the

PowerPAD package and its thermal properties, see

either the application brief SLMA004B (PowerPAD

The PowerPAD package is a thermally enhanced

Made Easy) or technical brief SLMA002 (PowerPAD

standard size IC package designed to eliminate the

Thermally Enhanced Package).

use of bulky heatsinks and slugs traditionally used in

thermal packages. This package can be easily

mounted using standard printed circuit board (PCB)

assembly techniques and can be removed and

replaced using standard repair procedures.

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