AQ120
Battery Charger Controller
SOT23-5 and SC70-5 Package
Preliminary Specification
Revision 1.8
April 1, 2006
General Description
The AQ120 is a low cost linear battery
charger controller with similar features to
the industry standard “1734” style
controller, but with the extra ability to
charge multiple cell Lithium Ion batteries
as well as NiCad types. In addition, the
maximum Vin is 18 volts. The AQ120
flexibility allows the setting of the charge
voltage and current with a minimum
number of external components.
The open collector output is capable of
driving an external PNP transistor. A
temperature stable bandgap reference
(1.25 V) controls the maximum output
voltage, while a current control circuit
sets a constant charging current.
Applications
•
Battery chargers
Features
•
1.25V reference with 1% accuracy
•
Multiple cell compatible
•
Programmable charge current
•
Low current consumption
•
Offered in ultra small SC70-5 package
•
No blocking diode required
•
Wide Vin range: 2.5V to 18V
•
25mA drive current sink
•
No battery drain in shutdown
•
Sleep mode with input supply removal
•
RoHS compliant
available
Pin Configuration
Block Diagram
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AQ120
Acutechnology Semiconductor Inc.
AQ120
Typical Application
Note: The values of R1and R2 set the charge voltage (up to three Li-Ion cells is possible). The value of R3 sets
the charge current.
Pin Descriptions
Pin
1
2
3
4
5
Pin Name
DRIVE
GND
IPROG
VCC
VREF
Function
Output of error amplifier. 25 mA sink capability
Ground
Current programming pin, has a threshold of 200 mV.
Positive supply
Voltage programming pin; has a threshold of 1.25V.
Ordering Information
Device
AQ120
AQ120
AQ120
AQ120
Note:
The
Operating Tj
-20C˚
≤
105C˚
-20C˚
≤
105C˚
-20C˚
≤
105C˚
-20C˚
≤
105C˚
%Tol
1.0
1.0
1.0
1.0
Pkg Type
SOT-23-5
SOT-23-5
SC70-5
SC70-5
V
OUT
1.25V
1.25V
1.25V
1.25V
Wrap
T&R
T&R
T&R
T&R
Order Number
AQ120DY-M5-AJ-TR
AQ120DY-M5-AJ-TRL
AQ120DY-C5-AJ-TR
AQ120DY-C5-AJ-TRL
TRL parts are Lead Free and RoHS compliant.
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Rev. 1.8
April 1, 2006
Acutechnology Semiconductor Inc.
AQ120
Absolute Maximum Ratings
Parameter
V
CC
Voltage
DRIVE Voltage
REF Voltage
VCC, DRIVE, REF Current
Operating Junction Temperature
Lead Temperature (soldering 10 seconds)
Storage Temperature Range
Value
18
18
18
50
150
300
-80 to +150
Units
V
V
V
mA
ºC
ºC
ºC
Electrical Specifications
Electrical characteristics are guaranteed over the full temperature range –20ºC <Tj< 105ºC. Ambient
temperature must be de-rated based upon power dissipation and package thermal characteristics.
Unless otherwise stated, test conditions are V
CC
= 5V, V
DRIVE
= 4.3V, V
IPROG
= 0V.
Symbol
Vcc
Icc
V
REF
TC
REF
Ln
REG
I
REF
V
DRV
low
I
DRIVE
I
LEAK
V
IPROG
Gain
I
IPROG
Parameter
Supply Voltage Range
Vcc Quiescent Supply
Current
Reference Voltage
Reference Temperature
Deviation
Reference variation with
Supply Voltage
Reference input current
Output Saturation Voltage
Drive Current
Output Leakage Current
IPROG threshold voltage
Delta Vref / V
IPROG
I
PROG
input current
V
REF
= V
CC
= V
DRIVE
= 5V
Ta=25ºC
-20ºC <Tj<105ºC
VCC=2.5V to 18V
I
DRIVE
= 500 µA
V
REF
= 0V
I
DRIVE
= 10 mA, V
REF
= 0V
V
DRIVE
= 5V,
V
REF
= V
IPROG
= GND
V
DRIVE
= V
REF
= V
CC
= 18V
Tj=25ºC
-20<Tj<105ºC
T=25ºC
-20<Tj<105ºC
V
IPROG
= 0V
V
IPROG
= -250 mV
190
195
36
20
-50
1.238
Conditions
Min
2.5
Typ
5
150
1.250
0.5
0.3
-20
1.8
25
200
200
200
40
40
-50
-160
400
210
205
44
2.2
Max
18
300
1.263
1
0.6
Units
V
µA
V
%
mV/V
nA
V
mA
nA
mV
mV/
mV
µA
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Rev. 1.8
April 1, 2006
Acutechnology Semiconductor Inc.
AQ120
Typical Performance Characteristics
900
800
700
600
500
400
300
200
100
2
V 2/V
2.2
2.4
2.6
2.8
3
3.2
3.4
Charge c urrent v s battery v oltage
1 c ell Lithium Ion battery
3.6
3.8
4
4.2
200mV /div
Cons tant v oltage mode
Cons tant c urrent mode
Fig.1 Charge current vs battery voltage
4
3.5
3
2.5
2
1.5
1
900
700
500
300
100
0
1
2
3
Constant current
Constant voltage
4
Fig. 2 Battery charge vs time
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Rev. 1.8
April 1, 2006
Acutechnology Semiconductor Inc.
AQ120
Operation
The AQ120 is a linear battery charger controller. Charging begins when Vcc rises above
2.5V. When charging, the collector of the external PNP transistor provides the charge current.
Below the target charge voltage the controller is in current mode. When the battery voltage
reaches the target voltage then the controller switches to the voltage mode.
The target voltage is programmable through an external resistor divider. This allows flexibility
to set the voltage (to one or more cells Li ion batteries, NiMH or NiCd batteries).
In current mode the AQ120 regulates the voltage across the sense resistor to be 200 mV.
The charge current is therefore given by Ich = 0.2V / Rsense. An additional resistor is
recommended (as in the typical application diagram) for stability reasons, then the threshold
is actually increased by the value of the resistor multiplied by the current out of the IPROG
pin. The AQ120 is designed for a maximum current in excess of 1A. The external PNP
transistor must have adequate beta, low saturation voltage and sufficient power dissipation
capability. With low supply voltages, the PNP saturation voltage becomes important as well.
In constant voltage mode, the controller will control the battery voltage not to exceed the
target charge voltage.
When Vcc is applied, the charger can be manually shut down by opening the resistor R2 of
the resistor divider (floating the otherwise grounded end of R2) or by pulling high the REF pin.
This can be used in conjunction with an external thermostat switch.
When input power is removed or manual shutdown is entered, the charger will drain only very
small leakage currents from the battery, thus maximizing battery standby time. The leakage
current is due to the reverse-biased base-emitter junction of the external PNP transistor.
A LED indicator can be added to show when the charger is operational, simply connecting
the base-emitter of an additional PNP transistor in parallel to the base-emitter of Q1 and its
collector to the LED.
The AQ120 contains two control loops. To maintain good AC stability in the constant voltage
mode, a capacitor of at least 10uF in series to a 3.3 ohms resistor is usually required from the
collector of the external PNP to ground. The stability of the system is also depending on the
type of external PNP transistor. High beta PNPs may be reducing the phase margin in some
cases. R6 and C3 insure system stability in current mode without affecting the voltage mode.
The use of the resistor R6 affects the threshold. For example for R6=150 ohms the threshold
moves from 200 mV to 215 mV.
Furthermore the use of an external PMOS in place of the PNP represents a valid alternative
to the application when wanting to minimize the current consumption during charge.
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Rev. 1.8
April 1, 2006
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