AD8450ASTZ datasheet(36/42 Pages) AD

36 / 42 page

Data Sheet

AD8450

Rev. B | Page 35 of 41

Table 8. AD8450-EVALZ Test Switches and Their Functions

Switch

Function

Operation

Default

Position1

ISGN

PGIA gain switch

The ISGN switch selects one of four fixed gain values: 26, 66, 133, or 200.

User select

BVGN

PGDA gain switch

The BVGN switch selects one of four fixed gain values: 0.2, 0.27, 0.4, or 0.8.

N/A

IS_REF

Selects between offset options for

the PGIA

NORM: 0 V reference.

NORM

20mV: offsets the PGIA reference by 20 mV.

EXT: An externally supplied reference voltage is applied to the PGIA.

BV_REF

Selects input source option for

the BVREFH pin

NORM: Overvoltage (OV) reference applied.

NORM

5mV: The BVDA is offset by 5 mV.

EXT: An externally supplied reference voltage is applied to the BVDA.

MODE

Selects charge or discharge mode

The MODE switch selects CHG (logic high) or DISCH (logic low).

CHG

RUN_TEST1 Configures the ISET and VSET

inputs to test the integrators.

RUN: The ISET and VSET inputs are connected to SMA connectors ISET

and VSET.

RUN

TEST: connectors the ISET and VSET inputs to the 2.5 V reference.

RUN_TEST2 Configures the ISET and VSET

outputs to test the integrators.

RUN: configures the ISET and VSET outputs as integrators.

RUN

TEST: configures the ISET and VSET outputs as followers.

N/A means not applicable.

Table 9. AD8450-EVALZ SMA Connector Functions

Connector

Function

ISVP

Input from the battery current sensor to the PGIA positive input.

ISVN

Input from the battery current sensor to the PGIA negative input.

BVP

Input from the battery positive voltage terminal to the PGDA positive input.

BVN

Input from the battery negative voltage terminal to the PGDA negative input.

ISET

Input to the AD8450 ISET pin.

VSET

Input to the AD8450 VSET pin.

VCTRL

AD8450 control voltage output to the PWM or analog power supply COMP input.

CS_BUS

AD8450 current sharing input/output bus.

PGIA in an Application

The differential inputs of the PGIA assume the use of a high-

side current shunt in series with the battery. To connect the

evaluation board in an application, simply connect the ISVP

and ISVN to the positive and negative shunt connections. Be

sure that both inputs are floating (ungrounded). The ISVP and

ISVN inputs tolerate the full AVCC common-mode voltage

applied to the board.

Simple Offset Test

Short the PGIA inputs from TPISVP to TPISVN to one of the

black ground loops. The ISMEA output is 0 V ± the residual

offset voltage multiplied by the gain. Move the IS_REF switch

to the 20 mV position to increase ISMEA by 20 mV.

Offset in an Application

In certain instances, the system operates with various ground

voltage levels. Although the PGIA is differential and floating, it

may be advantageous to refer the PGIA to a ground at or near

the battery load.

PGDA and Offset

Simple Test

The PGDA has four gain options (0.8, 0.4, 0.27, and 0.2) selected

with the four-position BVGN slide switch. Set the BV_REF

switch to the NORM position. Test the PGDA amplifier in the

same manner as PGIA. Apply 1 V dc between TPBVP and TPBVN.

Measure the output voltages at TPBVMEA. The output voltages

are 0.8 V, 0.4 V, 0.27 V, and 0.2 V, respectively, at the four BVGN

switch positions.

PGDA in an Application

For connection to an application, simply connect the input

terminal across the battery. It is good practice to take advantage of

the differential input to achieve the most accurate measurements.

PGDA Offset

The BV_REF offset works just the same as the IS_REF except

that the fixed offset is 5 mV. Simply use the BV_REF switch to

select the option. For an external offset reference, move the

BV_REF switch to EXT and connect a wire from the TPBREFL

and TPBREFH test loops to the desired reference points.

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