Preliminary Technical Data

AD8250

Rev. PrB| Page 7 of 8

PIN CONFIGURATIONS AND FUNCTIONAL DESCRIPTIONS

AD8250

TOP VIEW

(Not to Scale)

-IN

1

DGND

2

-VS

3

A0

4

A1

5

+IN

VREF

+VS

VOUT

WR

10

9

8

7

6

Figure 4. 10-Lead MSOP

Table 3. Pin Function Descriptions—

10-Lead MSOP(ARM PACKAGE)

Pin No.

Name

Description

1

-IN

Inverting Input Terminal (True

differential input)

2

DGND

Digital Ground.

3

-Vs

Negative Supply Terminal

4

A0

Gain Setting Pin (LSB)

5

A1

Gain Setting Pin (MSB)

6

WR

Write Enable

7

VOUT

Output Terminal

8

+Vs

Positive Supply Terminal

9

VREF

Reference Voltage Terminal (drive this

pin with a low impedance voltage

source to level shift the output signal)

10

+IN

Non-inverting Input Terminal (True

differential input)

GAIN SETTING

The AD8250’s gains are set digitally. The A0 and A1 pins must

be set either HIGH or LOW with respect to digital ground,

DGND. The WR pin is a tri-state switch. It may be set to one of

three levels, HIGH, LOW or to –VS. A HIGH signal is typically

greater than 4V but less than 6V and a LOW signal is typically

less than 1V but higher than DGND, 0V. Gains can be

programmed using the following methods:

TRANSPARENT GAIN SETTING MODE:

In this mode, the gain is set by toggling A0 and A1 to HIGH or

LOW. To enable transparent mode, tie WR to –Vs. This

configures the AD8250 to change gains when A0 and A1 are set

according to Table 4.

Table 4. . Transparent Mode Gain Settings

G

WR

A1

A0

1

-Vs

LO

LO

2

-Vs

LO

HI

5

-Vs

HI

LO

10

-Vs

HI

HI

WRITE ENABLE GAIN SETTING MODE:

In this mode, the gains are changed only during the negative

edge of the WR strobe. So for instance, the gain is determined

by the two bit value held on A0 and A1 at the time the WR

strobe transitions from HIGH to LOW.

WR

A0, A1

Table 5. : Write Enable Mode Gain Settings

Gain (changes to)

WR

A1

A0

1

HI -> LO

LO

LO

2

HI -> LO

LO

HI

5

HI -> LO

HI

LO

10

HI -> LO

HI

HI

No Change

LO->LO

X

X

No Change

LO->HI

X

X

No Change

HI-> HI

X

X

X = don’t care

.