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Preliminary

RT9541

DS9541-05 August 2001

www.richtek-ic.com.tw

Li-Ion Battery Protector

General Description

The RT9541 Series are protection ICs for over-
charge/discharge of rechargeable one-cell Lithium-ion
(Li+) batteries by CMOS process.

The RT9541 Series can detect over-charge/discharge
of Li+ one-cell and excess load current and charge
current, further include a short circuit protector for
preventing large external short circuit current.

Each of these ICs is composed of four voltage
detectors, a reference unit, a hysteresis circuit, and a
bidirectional short circuit protector. Package of SOT-
26 is available.

Ordering Information

RT9541

Typical Application Circuit

Features

Low supply current

- Supply current: TYP. 2.0µµµµA
- Standby current (after detecting over-

discharge): Less than 0.2

µ
µ
µ
µA

High accuracy detector threshold

- Over-charge detector: ±±±±25mV
- Over-discharge detector: ±±±±2.5%

Built-in protection circuit

- Excess current trip/Short circuit protector in

both charging and discharging direction

Output delay of over-charge adjustable with
an external capacitor: 75mS at 0.01

µ
µ
µ
µF

Ultra small package: SOT26

Applications

Over-charge / Over-discharge Protection for Li+
One-cell Pack

High Precision Protectors for Cellular Phones or
Instruments Using Li+ One-cell Battery

Pin Configurations

Part Number

Pin Configurations

RT9541 CE

(Plastic SOT-26)

TOP VIEW

1. COUT
2. CT
3. VSS
4. DOUT
5. VDD
6. V-

RT9541 CER
(Plastic SOT-26)

TOP VIEW

1. DOUT
2. V-
3. COUT
4. CT
5. VDD
6. VSS

Operating temperature range

C: Commercial standard

Package type
E : SOT-26 Type I
ER : SOT-26 Type II

See Table 1

RT9541

VDD

VSS

DOUT

COUT

V-

R1
100

C1
0.1

µF

0.01

µF

0.1

µF

R2
1K

RT9541

Preliminary

www.richtek-ic.com.tw

DS9541-05 August 2001

Absolute Maximum Ratings

Allowable Battery Voltage

-0.3V ~ 7V

Input Voltage (V)

VDD-14V to VDD +0.3V

Input Voltage (CT)

VSS-0.3V to VDD +0.3V

Output Voltage (COUT)

VDD-14V to VDD +0.3V

Output Voltage (DOUT)

VSS-0.3V to VDD +0.3V

Power Dissipation, P

@ T

= 25

°C

SOT-26

0.25W

Package Thermal Resistance
SOT-26,

250

°C/W

Operating Temperature Range

-20

°C ~ +85°C

Storage Temperature Range

-65

°C ~ +150°C

Electrical Characteristics

Parameter

Symbol

Test Conditions

Min

Typ

Max

Units

Operating Input Voltage

Voltage defined as VDD-VSS

Charger Voltage

CHG

Voltage defined as VDD-V-

Minimum Operating Voltage for 0V

Charging

Voltage defined as VDD-V-
VDD-VSS = 0V

Accuracy of Over-charge

Threshold Voltage

OCHG

Detect rising edge of supply
voltage

-25

Over-charge Threshold Hysteresis

0.1

0.15

0.2

Output Delay Time of Over-charge T

OCHG

C3 = 0.01

µF, VDD = 3.6V ~

4.3V

Accuracy of Over-discharge

Threshold Voltage

ODISCHG

Detect falling edge of supply
voltage

-2.5

2.5

Output Delay Time of Over-

discharge

ODISCHG

VDD = 3.6V ~ 2.4V

Excess Current Threshold Voltage

During Discharge

Detect rising edge of "V-" pin
voltage

0.15

0.17

0.19

Output Delay of Discharge Excess

Current

VDD = 3.0V

Excess Current Threshold Voltage

During Charge

Detect falling edge of "V-" pin
voltage

-0.19

-0.17

-0.15

Output Delay of Charge Excess

Current

Short Detection Voltage During

Discharge

VDD = 3.0V

VDD-1.1 VDD-0.8 VDD-0.5

Output Delay of Discharge Short

Circuit

SHORT

VDD = 3.0V

µS

Reset Resistance for Excess

Current Protection

SHORT

VDD = 3.6V, V- = 1.0V

Supply Current

VDD = 3.9V, V- = 0V

2.0

5.0

µA

Standby Current

STANDBY

VDD = 2.0V

0.1

0.5

µA

Preliminary

RT9541

DS9541-05 August 2001

www.richtek-ic.com.tw

Table 1

Part Number

Over

Charge

Over

Discharge

Excess

Current

RT9541ACE (R)

4.25V

2.3V

170mV

RT9541BCE (R)

4.25V

2.4V

170mV

RT9541CCE (R)

4.25V

2.5V

170mV

RT9541DCE (R)

4.25V

2.6V

170mV

RT9541ECE (R)

4.25V

2.7V

170mV

RT9541FCE (R)

4.25V

2.8V

170mV

RT9541GCE (R)

4.30V

2.3V

170mV

RT9541HCE (R)

4.30V

2.4V

170mV

RT9541ICE (R)

4.30V

2.5V

170mV

RT9541JCE (R)

4.30V

2.6V

170mV

Part Number

Over

Charge

Over

Discharge

Excess

Current

RT9541KCE (R)

4.30V

2.7V

170mV

RT9541LCE (R)

4.30V

2.8V

170mV

RT9541MCE (R)

4.35V

2.3V

170mV

RT9541NCE (R)

4.35V

2.4V

170mV

RT9541OCE (R)

4.35V

2.5V

170mV

RT9541PCE (R)

4.35V

2.6V

170mV

RT9541QCE (R)

4.35V

2.7V

170mV

RT9541RCE (R)

4.35V

2.8V

170mV

RT9541SCE (R)

4.35V

2.9V

170mV

RT9541TCE (R)

4.25V

2.9V

170mV

Function Block Diagram

Pin Description

Pin Number

RT9541- CE RT9541- CER

Pin Name

Pin Function

COUT

Output of Over-charge Detection, CMOS Output

Pin for External Capacitor Setting Output Delay of VD1

VSS

Ground

DOUT

Output of Over-discharge Detection, CMOS Output

VDD

Power Supply, through a Resistor (R1)

V-

Pin for Charger Negative Input, through a Resistor (R2)

Short

Circuit

Detector

Level Shift

Delay

VDD

VD1

VD4

VD2

VD3

VSS

DOUT COUT

V-

RT9541

Preliminary

www.richtek-ic.com.tw

DS9541-05 August 2001

Applications Information

(1) Operation Description

Refering to the "Function Block Diagram", when
charging voltage crosses the detector threshold from
a low value to a value higher than VDET1, the output
of COUT pin, the output of over-charge detector/VD1,
swiches to low level,..charger's negative pin level.
After detecting over-charge the VD1 can be reset and
the output of COUT pin becomes "H" when the VDD
voltage is coming down to a level lower than "VDET1
VHYS1", or when a charger is disconnected from
the battery pack.

The output of DOUT pin, the output of over-discharge
detector/VD2, switches to "L" after internally fixed
delay time passed, when discharging voltage crosses
the detector threshold from a high value to a value
lower than VDET2. An excess load current can be
sensed and cut off after internally fixed delay time
passsed through the built in excess current detector,
VD3, with DOUT being enabled to low level. Once
after detecting excess current, the VD3 is released
and DOUT level switches to "H" by detaching a
battery pack from a load system.

Futher, short circuit protector makes DOUT level to
"L" immediately with external short circuit current and
removing external short circuit leads DOUT level to
"H".

The excess charging current is also monitored, and
the charging path will be cut off (by turn low COUT)
after excess charging current was detected lasting a
internally fixed delay time. The charging path will be
re-started (by turn high COUT) after another
internally fixed delay. If the excess charging current is
still there, the same process will be repeated and
cause the charging path toggling on and off with a
12.5% on duty. Such a protection function reduces
the average charging current to 12.5% of original
value when excess charging current detected.

The short circuit protection function in charging
direction was also provided. When COUT high and
the "V-" pin voltage 5V lower than VSS pin, the
RT9541 will turn low COUT with a fixed delay. The
COUT will go high after the short circuit condition
was removed.

After detecting over-discharge, supply current will be
kept extremely low by halting some internal circuits
operation. The output delay of over-charge detectors
can be set by connecting an external capacitor.
Output type of COUT and DOUT are CMOS.

(2) Component Selection Guide:

Referring to "Typical Application Circuit", R1 and
C1 will stabilize a supply voltage to the RT9541. A
recommended R1 value is less than 1k. A larger
value of R1 leads higher detection voltage, makes
some errors, because of shoot through current
flowed in the RT9541.

R2 and C2 will stabilize a V- pin voltage. The
resetting from over-discharge with connecting
charger possibly be disabled by larger value of R2.
Recommended value is less than 1k. And
recommended C2 value is less than 1

µF.

R1 and R2 can operate as a current limiter against
setting cell reverse direction or for applying excess
charging voltage to the RT9541. While smaller R1
and R2 may cause an over power dissipation rating
of the RT9541 and a total of "R1+R2" should be
more than 1k.

Document Outline

Ð­Ð»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: RT9541RCER

Document Outline

ÐÐ»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: RT9541RCER