PT8A2704WE

PT8A2704/04A

|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||

Simple Fast Charger Controller

Product Features





Fast charge of nickel cadmium (NiCd) or nickel-

metal hydride (NiMH) batteries

Fast-charge termination by negative delta voltage,

maximum voltage, maximum temperature, and 90

minutes charging time













Support 1 to 8 cells fast charging

10% (PT8A2704) or 4% (PT8A2704A) of constant

charging current for trickle charging

On-chip 2.0V regulator

On chip precise ADC

Internal RC oscillator with external R&C

components

Low cost 8-pin DIP/SOIC package

Product Description

The PT8A2704/04A Fast-Charger IC is low-cost CMOS

battery-charge controller providing reliable charge

termination

for

both

NiCd

and

NiMH

battery

applications, such as Power tool and Consumer

electronics. A current-limited or constant–current supply

allows the PT8A2704/04A to be a cost-effective charger

with

only

a

few

external

components.

The

PT8A2704/04A has programmable charging time and

programmable trickle charging rate control by options in

a single IC for charging NiCd or NiMH battery cells.

For safety, fast or trickle charging is inhibited if the

battery temperature is over a safety threshold. Fast

charge is terminated by any of the following:

- Negative delta voltage/zero delta voltage

- Maximum voltage

- Maximum temperature

- Maximum time

Applications







Rechargeable shavers and hair cutters

Rechargeable RC cars

Rechargeable power tools

Pin Assignment and Pin Description

Pin Description

PT8A2704/04A

DIP-8 or SOIC-8

Package (Top View)

Pin

No.

1

2

3

4

5

6

7

8

Pin

Name

GND

VB

VT

OSC

CORD

VCC

CHARGE

VEE

I/O

-

I

I

I

I

-

O

O

Description

Power ground

Battery voltage input (1.6V – 1.8V)

NTC voltage input(1.6V – 1.8V)

RC oscillator input, external resistor

pull-up and capacitor pull-down

Cord detection input

Positive power supply voltage

Charging control enable

2.0v regulated voltage

12-07-0005

1

PT0199-8

07/05/12

PT8A2704/04A

Simple Fast Charger Controller

|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||

Block Diagram

Functional Description

Voltage Regulator (2.0V Regulator):

Build-in voltage regulator used to power supply RC oscillator, precise ADC.

Oscillator:

Internal RC oscillator to generate a 64 kHz clock for internal system.

POR (Power-on Reset):

Power on reset to reset all internal logic while power on.

Charging Control:

Charging control enables output CHARGE pin which can be used to show charging status. It is logic high

during constant current charging and 12.5Hz with 10% (for PT8A2704) or 4% (for PT8A2704A) duty cycle during trickle current

charging

AC Cord Control:

CORD input is external cord detection pin (digital level), active high.

Precision ADC:

VB

measures the battery voltage. VB is a divide voltage from the battery voltage. When VB exceeds the maximum voltage

(0.9VEE), fast charging will be terminated. Moreover, VB detects the negative delta voltage during fast charging. It is suggested

to set the termination voltage of VB within the input range of the ADC which is 0.8VEE to 0.9VEE.

VT

measures the temperature of the battery with an external NTC (refer to

How to determine RX1 on page5).

Maximum

temperature termination occurs when the VT exceeds a temperature cut-off threshold voltage (eg. 50˚C which equivalent to

0.887VEE). Constant current or trickle charging will stop completely when the temperature exceeds another threshold voltage (eg.

55˚C which equivalent to 0.897VEE).

Charging Cycle Phases

No charging

Fast charging

Pulse-trickle

Stop charging

CORD

CHARGE

Fast charge is started when the CORD is high. If the battery voltage is over the limit or temperature exceeds 50˚C, pulse-trickle

charge begins and the device charges the battery with trickle charge till the CORD is low (see above Figure).

Fast charge will be termination by one or more of the four possible termination conditions:



negative delta voltage/delta voltage



maximum voltage



maximum temperature



maximum time

12-07-0005

2

PT0199-8

07/05/12

PT8A2704/04A

Simple Fast Charger Controller

|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||

Maximum Ratings

Storage Temperature…………………………………………... -25oC to +85oC

Supply Voltage to Ground Potential (V

CC

)…………. ……………...…-0.5V to 6V

DC Input Voltage…………………… ……………..……… -0.5V to V

CC

+0.5V

DC Output Current……………………………………………....20mA

Power Dissipation…………………………………………...…500mW

Note:

Stresses greater than those listed under MAXIMUM

RATINGS may cause permanent damage to the

device. This is a stress rating only and functional

operation of the device at these or any other condi-

tions above those indicated in the operational sec-

tions of this specification is not implied. Exposure

to absolute maximum rating conditions for extended

periods may affect reliability.

Recommended Operation Condition

Parameters

V

CC

ADC V

IN

Fosc

T

A

Description

Operating Voltage

Input voltage range (VT, VB)

Frequency of oscillator (C=390pF, R=47kΩohm)

Operation Temperature

Min.

2.2

0.8

54.4

0

Type.

2.4

-

64

25

Max.

5.5

0.9

73.6

70

Unit

V

VEE

kHz

˚C

DC Electrical Characteristics

(T

A

= 0~70° V

CC

= 2.4V unless otherwise claims)

C,

Symbol Description

Input Low/HIGH leakage current for

I

IL

, I

IH

CORD pin

I

OH

Output HIGH current

I

OL

Output LOW current

VEE Regulator output voltage

Line Regulation of regulator

V

O

Load regulation

Maximum battery voltage to stop fast-

VBmax

charge

Maximum VT voltage for battery

VTmax temperature detection to stop fast-

charge

Rslt

Average A/D resolution of ADC

DNL ADC Differential nonlinearity

INL

ADC Integral nonlinearity

I

CC

Supply Current

V

LDR

Test Conditions

V

CC

=2.4V,V

IL

=0.2V, V

IH

=2.2V

CHARGE pin, V

OH

=2.2V

CHARGE pin, V

OL

=0.2V

No load

2.2VV

CC

3.0V,

No load

0mA



I

L

3mA

-

-

No load

No load

No load

R=47kΩ, C=390pF, no load

Min.

-1

-3

3

1.9

-

-

-

-

6.00

-

-

-

Typ.

-

-

-

2.0

-

-

0.9

0.897

6.25

1

1

-

Max.

1

-

1

2.1

50

50

-

-

6.50

-

-

380

Unit

μA

mA

V

mV

mV

VEE

VEE

mV

LSB

LSB

μA

AC Electrical Characteristics

(T

A

= 0~70° V

CC

= 2.2V~3.0V)

C,

Symbol Description

F

OSC

Oscillator Frequency

T

FC

Maximum fast-charge time

DC

Test Conditions

C=390pF, R=47kΩ

OSC=64kHz

Duty-cycle of charge pin output in PT8A2704

trickle charge mode

PT8A2704A

Min.

54.4

-

7

3

Typ.

64

90

10

4

Max.

73.6

-

13

5

Unit

kHz

Minutes

%

%

12-07-0005

3

PT0199-8

07/05/12

PT8A2704/04A

Simple Fast Charger Controller

|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||

Typical Application Circuit

1. Application circuit for larger discharging current.

PT8A2704/04A Application Circuit for Shaver with Two Batteries

Note:

a. R1 value can be adjusted to make sure the CORD voltage is around 2.0V.

b. As the device is always powered by battery, the static consumption must be considered in application design.

12-07-0005

4

PT0199-8

07/05/12

PT8A2704/04A

Simple Fast Charger Controller

|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||

2. Application circuit for smaller discharging current.

If discharging current is smaller, suggest using the following schematic:

PT8A2704/04A Application Circuit for Shaver with Two Batteries

PCB Layout Constraint

1. Cross angle between two Tracks should be larger than 90 degree.

2. Track should be short and wide enough to reduce voltage drop, especially Power supply and Ground as well as some tracks

flowing with large current, such as switch Q1.

3. A ceramic cap C6 about 103 need to add between VT and Ground of PT8A2704 in order to prevent detection circuit from noise.

4. A ceramic cap C7 about 103 and C8 10μF Tan cap need to add between VB to Ground.

How to determine RX1

Assuming Resistance of NTC at 55˚C is RT.

See right figure, below formula can be attained.

VT=RX1*VEE/ (RX1+RT) =1.8V

VEE=2.0V, finally

RX1=9*RT

VEE

NTC

VT

RX1

12-07-0005

5

PT0199-8

07/05/12