AD8452 datasheet(29/35 Pages) AD

29 / 35 page

AD8452

Data Sheet

Rev. 0 | Page 28 of 34

APPLICATIONS INFORMATION

ANALOG CONTROLLER

This section describes how to use the AD8452 in the context of

a battery formation and test system and includes design

examples.

FUNCTIONAL DESCRIPTION

The AD8452 is a precision analog front end and controller for

battery formation and test systems. Such systems are differentiated

from typical battery charger or battery management systems by

the high level of voltage and current measurement precision

required to optimize Li-Ion batteries for capacity and energy

density. Figure 49 shows the analog signal path of a simplified

switching battery formation and test system using the AD8452

controller.

The AD8452 is suitable for systems that test and form Li-Ion

and the legacy NiCad and NiMH electrolyte batteries. The

output is a digital format (PWM), designed to drive a switching

power output stage.

The AD8452 includes the following blocks (see Figure 33 and

the Theory of Operation section for more information):

•

A fixed gain in-amp that senses low-side or high-side

battery current.

•

A fixed gain difference amplifier that measures the

terminal voltage of the battery.

•

Two loop filter error amplifiers that receive the battery target

current and voltage and establish the dynamics of the CC and

CV feedback loops.

•

A minimum output selector circuit that combines the outputs

of the loop filter error amplifiers to perform automatic CC

to CV switching.

•

A PWM with high- and low-side half bridge logic level

outputs suitable for driving a MOSFET gate driver.

•

A 2.5 V reference whose output node is the VREF pin.

•

A logic input pin (MODE) that switches the controller

configuration between charge mode (high) and discharge

mode (low).

BATTERY

VCTRL

CURRENT

SENSE

SHUNT

CLP

CLN

BVP

BVN

MODE

SWITCHES

(3)

BATTERY

CURRENT

(IBAT)

AVEE

CONSTANT CURRENT

LOOP FILTER AMPLIFIER

1×

VINT

BUFFER

ISET

VINT

ISMEA

BVMEA

AD8452

CONTROLLER

SET

BATTERY

VOLTAGE

SET

BATTERY

CURRENT

COMPENSATION

MATRIX

C = CHARGE

D = DISCHARGE

CONSTANT VOLTAGE

LOOP FILTER AMPLIFIER

AVCC

DC TO DC

POWER CONVERSION

BUCK

BOOST

PWM

LEVEL

SHIFTER

SELECT

IBAT

POLARITY

1.1mA

VREG

ISVP

ISVN

OUTPUT

SWITCHES

LPF

CURRENT

LIMIT AND

DIODE

EMULATION

RCL

1×

PGDA

PGIA

Figure 49. Complete Signal Path of a Battery Test or Formation System Suitable for Li-Ion Batteries

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