Datasheet

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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 µ s (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 more detailed information regarding the
PowerPAD package and its thermal properties, see
either the application brief SLMA004 B ( 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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