BUF11702PWPR datasheet(21/25 Pages) TI2

21 / 25 page

BUF11702

BUF07702

SLOS359F − MARCH 2001 − REVISED MAY 2004

www.ti.com

REFERENCE VOLTAGES

The reference voltages can be supplied externally via

the connector J2 (not included) or generated onboard

via resistors R1 to R11. An external low side reference

has been provided on the board so that the negative ref-

erences can be referred to a voltage other than ground.

The reference ladder can be referred to either VDD

(master supply voltage) or a secondary voltage, VDD2.

This allows a low noise or absolute reference voltage to

be used for the LCD source driver’s DACs other than

the system voltage. If the secondary voltage is used,

then jumper JP1 should be left open and jumper JP2

shorted. If a ratiometric reference (proportional to the

master supply voltage) is to be used, then jumpers JP1

and JP2 should both be shorted, feeding VDD through to

the reference ladder.

OUTPUT

The outputs of the BUF11702 are fed to connector J3

(not mounted). This enables the output voltages to be

monitored directly on the demonstration board or fed

off-board for evaluation in a real system.

Onboard load resistors, R23 to R32, connected to

ground can also be mounted. These can be used to sim-

ulate resistive loading of the LCD source driver.

Transient improving capacitors are frequently used in

LCD panel applications. Therefore, pads to mount

these transient improving capacitors, C6 to C16, have

been included. Due to the possible magnitude of these

capacitors, pads have been placed between the output

of the BUF11702 and these capacitors to mount nulling

resistors, R12 to R22. If the nulling resistors are not re-

quired, shorts could be placed instead of resistors.

The pads for R1 to R32 and capacitors C3 to C16 have

been laid out to support 0805 or 1206 size components.

PowerPAD

The BUF11702 demonstration board has been laid out

to support the PowerPAD feature of the BUF11702. An

area is provided on the demo board, under the

BUF11702, for the exposed leadframe connection.

Eighteen vias are connected to the ground plane of the

demo board to significantly reduce the thermal case to

ambient resistance,

qCA. See the Applications section

on general PowerPAD design considerations.

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