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STATIN_L = V

SUP_H

R1 + R2

(

STATIN_L = V

SUP_L

R3 + R4

(

BUF22821EVM-USB Features

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4.6 JMP6: STATIN_H Control Setting

Jumper JMP6 is selects where the BUF22821 high reference supply pin STATIN_H is connected. If JMP6

is set to the INT position, STATIN_H is connected to V

, the external analog supply input at terminal T1.

When JMP6 is set to the EXT position, the reference voltage is then designated by the user with the

STATIN_H pin of terminal T4, along with resistors R1 and R2. An external power supply is connected to

the STATIN_H pin of terminal T4, and R1 and R2 act as a voltage-divider circuit; the user sets the values

of R1 and R2 to achieve the desired reference voltage using Equation 1:

(1)

Where V

SUP_H

is the input supply voltage seen at the STATIN_H pin of terminal T4.

4.7 JMP7: STATIN_L Control Setting

Jumper JMP7 is selects where the BUF22821 high reference supply pin STATIN_L is connected. If JMP8

is set to the INT position, STATIN_L is connected to ground.

When JMP7 is set to the EXT position, the reference voltage is then designated by the user with the

STATIN_L pin of terminal T4, along with resistors R3 and R4. An external power supply is connected to

the STATIN_L pin of terminal T4, and R3 and R4 act as a voltage-divider circuit; the user sets the values

of R3 and R4 to achieve the desired reference voltage using Equation 2:

(2)

Where V

SUP_L

is the input supply voltage seen at the STATIN_L pin of terminal T4.

4.8 BUF22821 Device Placement

The BUF22821EVM-USB provides two separate locations on the board where the BUF22821 test device

can be installed.

Location U1 allows for a BUF22821 device that is soldered down on a DIP adaptor board to be installed

on the BUF22821 Test Board. The output capability of the BUF22821 that is soldered on this adaptor

board can be fully evaluated. The PowerPAD™ of this soldered BUF22821 is connected correctly and

allows the device to dissipate the necessary power while being evaluated.

Location U2 on the BUF22821 Test Board is a 24-pin, QFN-package test socket that allows the user to

evaluate and program many devices very quickly. One drawback to this socket is that there is no

connection to the PowerPAD of the BUF22821. Because of this limitation, while the device is placed in this

socket, it cannot be operated to its full output capability as a result of thermal dissipation limitations.

CAUTION

Only one location should be populated at a time. The use of both locations

simultaneously will likely damage one or both of the devices under test.

4.9 Terminal Strip TP1

Terminal strip TP1 provides the individual output signals on a single row of headers as well as a row of

vias. This footprint offers the user multiple options to interface the output signals of the BUF22821 with an

available display panel (provided by the user). The user can also develop a custom cable to connect the

headers to this panel directly, or to solder the headers directly to the individual vias.

BUF22821EVM-USB Evaluation Board and Software Tutorial SBOU117–September 2011

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