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PS200-I/SO

PowerSmart® Configurable Battery Charger

Microchip Technology 

1.0 PS200 OVERVIEW

The PS200 is a configurable Switch mode charger

which is comprised of a PIC16F microcontroller core

and precision analog circuitry. This section explores the

hardware features in relation to generic Switch mode

charging. Subsequent sections will describe the opera-

tion of the PS200 with firmware for Lithium-based

(Section 2.0 “Lithium Chemistry Algorithm”),

Nickel-based (Section 3.0 “Nickel Chemistry Algo-

rithm”) and Lead Acid (Section 4.0 “Lead Acid

Chemistry Algorithm”) charging.

• Oscillator

• Power-saving Sleep mode

• Power-on Reset (POR)

• Brown-out Reset (BOR)

• High-Endurance Flash/EEPROM Cell:

- 100,000 write Flash endurance

- 1,000,000 write EEPROM endurance

- Flash/Data EEPROM retention: > 40 years

• High-Speed Comparator module with:

- Two independent analog comparators

• Operational Amplifier module with two

independent op amps

• Two-Phase Asynchronous Feedback PWM

• Voltage Regulator

• 10-bit (9-bit plus sign) A/D Converter

• In-Circuit Serial Programming™ (ICSP™) via

two pins

1.1 Hardware Features

The PS200 features are well-suited for Switch mode

battery charging. The PS200 device’s block diagram

(Figure 1-1) is to be used in conjunction with the Switch

mode charger example (Figure 2-3, page 12).

• Current/Voltage Measurement Block – The

Current/Voltage Measurement Block consists of a

10-bit Analog-to-Digital converter, operational

amplifiers and a comparator. The output of this

block is fed into the Charge Control module.

Please refer to Figure 1-1.

The inputs into this block are to be connected as

described in Figure 2-3. The following signals are

inputs into this block:

- LOOPFBK – to comparator

- LOOPIN – to op amp and ADC

- CTRLIN – to op amp

- IFBINB – to op amp

- IFBINA – to op amp

- BATID – to ADC

- TEMP – to ADC

- CHGFBK – to comparator

PS200

The following signals are outputs from this block:

- IFBOUT – from op amp

• Charge Control Module:

- The charge control module generates a

Pulse-Width Modulated signal called CHGOUT.

Its frequency is configurable and can be set up

to 1 MHz. This signal is connected to an

external DC/DC buck converter.

• Voltage Regulator

- The integrated voltage regulator is designed

to work with unregulated DC supplies.

- There are guidelines that should be followed.

A series limiting resistor (RVDD) should be

placed between the unregulated supply and

the VDD pin. The value for this series resistor

(RVDD) must be between RMIN and RMAX as

shown in the following equation:

EQUATION 1-1:

RMAX = Vs(MIN) – 5V) * 1000

1.05 * (16 mA + I(led))

RMIN = Vs(MAX) – 5V) * 1000

.95 * (50 mA)

Where:

RMAX = maximum value of series resistor (ohms)

RMIN = minimum value of series resistor (ohms)

Vs(MIN) = minimum value of charger DC supply (VDC)

Vs(MAX) = maximum value of charger DC supply (VDC)

I(led) = total current drawn by all LEDs when

illuminated simultaneously

The 1.05 and .95 constants are included to compensate

for the tolerance of 5% resistors. The 16 mA constant is

the anticipated load presented by the PS200, including

the loading due to external components and a 4 mA

minimum current for the shunt regulator itself. The

50 mA constant is the maximum acceptable current for

the shunt regulator.

• The precision internal 8 MHz clock oscillator

eliminates the need for external oscillator circuits.

• In-circuit configurability utilizing 256 bytes of

on-board EEPROM.

• Power on Reset – The POR insures the proper

start-up of the PS200 when voltage is applied to

VDD.

• Brown-out Reset – The BOR is activated when

the input voltage falls to 2.1V; the PS200 is reset.

© 2005 Microchip Technology Inc.

DS21891B-page 3

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