ADS5541IPAPR datasheet(28/37 Pages) TI1

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SERIAL PROGRAMMING INTERFACE

Assembly Process

PowerPAD PACKAGE

Production Data

ADS5541

SBAS307C – MAY 2004 – REVISED FEBRUARY 2007

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

bottom of the IC. This provides an extremely low

The

ADS5541

has

internal

registers

for

the

thermal resistance path between the die and the

programming of some of the modes described in the

exterior of the package. The thermal pad on the

previous sections. The registers should be reset after

bottom of the IC can then be soldered directly to the

power-up by applying a 2

µs (minimum) high pulse on

PCB, using the PCB as a heatsink.

RESET (pin 35); this pulse also resets the entire

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

200k

Ω internal pullup resistor to AV

DD.

The

1. Prepare

the

PCB

top-side

etch

pattern

programming is done through a three-wire interface.

including etch for the leads as well as the

Table 2 shows the different modes and the bit values

thermal pad as illustrated in the Mechanical

to be written to the register to enable them.

Data section. The recommended thermal pad

dimension is 8mm × 8mm.

Note that some of these modes may modify the

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

shown in this data sheet.

13mils in diameter. The small size prevents

wicking of the solder through the holes.

Applying a RESET signal is absolutely essential to

3. It is recommended to place a small number of

set the internal registers to the default states for

25mil diameter holes under the package, but

normal operation. If the hardware RESET function is

outside the thermal pad area to provide an

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

additional heat path.

to ground, and it is necessary to write the default

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

connection

pattern

when

connecting

the

Write A000h (Address A, Data 000)

thermal vias to the ground plane. The spoke

Write B000h (Address B, Data 000)

pattern increases the thermal resistance to the

Write C000h (Address C, Data 000)

ground plane.

Write D000h (Address D, Data 000)

6. The

top-side

solder

mask

should

leave

Write E000h (Address E, Data 804)

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

vias to prevent solder wicking.

Write F000h (Address F, Data 000)

8. Apply solder paste to the exposed thermal

NOTE: This procedure is only required if a RESET

pad area and all of the package terminals.

pulse 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.

The PowerPAD package is designed so that the lead

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