Datasheet

UNISONIC TECHNOLOGIES CO., LTD
UB2017
Preliminary
CMOS IC
ONE-CELL STANDALONE
LINEAR LITHIUM BATTERY
CHARGER
„
6
DESCRIPTION
5
UTC UB2017 is a complete, constant current and constant voltage
linear charger for single cell lithium-ion batteries. Its small size and
ability to regulate low charge currents make UTC UB2017 especially
well-suited for portable applications using low capacity rechargeable
lithium-ion coin cells. Furthermore, UTC UB2017 is specifically
designed to work within USB power specifications.
No external sense resistor is needed, and no blocking diode is
required due to the internal MOSFET architecture. The charge
voltage is fixed at 4.2V, and the charge current can be programmed
externally with a single resistor. UTC UB2017 automatically
terminates a charge cycle when the charge current drops to 1/10th
the programmed value after the final float voltage is reached.
„
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4
1
2
3
SOT-26
FEATURES
Programmable Charge Current Up to 500mA.
No External MOSFET, Sense Resistor or Blocking Diode Required.
Complete linear charger in Thin SOT Package for Single Cell / Coin Cell Lithium-lon Batteries.
Constant Current / Constant Voltage Operation with Thermal Regulation to Maximize Charge Rate Without Risk
of Overheating.
Charges Single Cell Li-lon Batteries Directly form USB Port.
Preset 4.2V Charge Voltage with High Accuracy about ±1.2%.
Automatic Recharge.
2.9V Trickle Charge Threshold.
25µA Max Supply Current in Shutdown Mode.
Charge Status Output Pin.
ORDERING INFORMATION
Ordering Number
Lead Free
Halogen Free
UB2017L-xx-AG6-R
UB2017G-xx-AG6-R
Note: xx: Output Voltage, refer to Marking Information.
UB2017G-xx-AG6-R
Package
Packing
SOT-26
Tape Reel
(1)Packing Type
(1) R: Tape Reel
(2)Package Type
(2) AG6: SOT-26
(3)Output Voltage Code
(3) xx: Refer to Marking Information
(4)Halogen Free
(4) G: Halogen Free, L: Lead Free
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Copyright © 2012 Unisonic Technologies Co., Ltd
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Preliminary
CMOS IC
MARKING INFORMATION
PACKAGE
VOLTAGE CODE (Note)
SOT-25
AA: 4.2V
„
PIN CONFIGURATION
„
PIN DESCRIPTION
PIN NO.
PIN NAME
1
CHRG
2
GND
3
BAT
4
VCC
5
CHRGT
6
PROG
MARKING
DESCRIPTION
Open-Drain Charge Status Output. When the battery is charging, the CHRG pin is
pulled low by an internal N-channel MOSFET. When the charge cycle is completed, a
weak pull-down of approximately 20uA is connected to the CHRG pin, indicating an “AC
present” condition.
Ground.
Charge Current Output. Provides charge current to the battery and regulates the final
float voltage to 4.2V.
Positive Input Supply Voltage. Provides power to the charger. VCC can range from
4.25V to 6.5V and should be bypassed with at least a 1μF capacitor.
Open-Drain Charge Termination Status Output. When the battery is charging, the
CHRGT pin is pulled high by an external component such as an LED. After the charging
is completed, this pin is pulled low by internal N-channel MOSFET and it can be used
as a charging termination indicator.
Charge Current Program, Charge Current Monitor and Shutdown Pin.
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Preliminary
CMOS IC
BLOCK DIAGRAM
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Preliminary
CMOS IC
ABSOLUTE MAXIMUM RATING
PARAMETER
SYMBOL
RATINGS
UNIT
Input Supply Voltage
VCC
-0.3~+7.0
V
PROG Voltage
VPROG
-0.3~+7.0
V
BAT Voltage
VBAT
-0.3~+7.0
V
CHRG Voltage
VCHRG
-0.3~+7.0
V
BAT Short-Circuit Duration
Continuous
BAT Pin Current
IBAT
500
mA
PROG Pin Current
IPROG
500
µA
Junction Temperature
TJ
125
°С
Operating Ambient Temperature
TOPR
-40 ~ +85
°С
Storage Temperature
TS
-65 ~ +125
°С
Notes: 1. Absolute maximum ratings are those values beyond which the device could be permanently damaged.
Absolute maximum ratings are stress ratings only and functional device operation is not implied.
2. Pulse (μsec) noise exceeding the above input voltage (GND+7.0V) may cause damage to the IC.
„
THERMAL DATA
PARAMETER
Junction to Ambient
SYMBOL
θJA
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RATINGS
250
UNIT
°С/W
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Preliminary
CMOS IC
ELECTRICAL CHARACTERISTICS (VCC=5V, TA=25°С, unless otherwise specified)
PARAMETER
Input Supply Voltage
Input Supply Current
Regulated Output (Float) Voltage
BAT Pin Current
SYMBOL
VCC
ICC
VFLOAT
IBAT
TEST CONDITIONS
Charge Mode (Note 1), RPROG=10k
Standby Mode (Charge Terminated)
Shutdown Mode(RPROG Not
Connected, VCC<VBAT, or VCC<VUV)
IBAT=30mA, ICHRG=5mA
RPROG=10k, Current Mode
RPROG=2k, Current Mode
Standby Mode, VBAT=4.2V
Shutdown Mode (RPROG Not
Connected)
Sleep Mode, VCC=0V
VBAT<VTRIKL, RPROG=10k
RPROG=10k, VBAT Rising
From VCC Low to High
MIN
4.5
4.15
80
0
TYP
110
115
MAX
6.0
2000
500
UNIT
V
μA
μA
20
60
μA
4.20
100
500
±1
4.25
120
±6
V
mA
mA
μA
±0.5
±6
μA
±1
±6
μA
Trickle Charge Current
ITRIKL
10
mA
Trickle Charge Threshold Voltage
VTRIKL
2.8
2.9
3.0
V
VCC Undervoltage Lockout Threshold
VUV
3.8
V
VCC Undervoltage Lockout Hysteresis VUVHYS
120
mV
PROG Pin Rising
1.25
V
Manual Shutdown Threshold Voltage
VMSD
PROG Pin Falling
1.15
V
100
mV
VCC from Low to High
VCC–VBAT Lockout Threshold Voltage
VASD
VCC from High to Low
30
mV
0.1
mA/mA
RPROG=10k (Note 2)
C/10 Termination Current Threshold
ITERM
RPROG=2k
0.1
mA/mA
PROG Pin Voltage
VPROG RPROG=10k, Current Mode
0.8
1.0
1.2
V
CHRG Pin Weak Pull-Down Current
ICHRG VCHRG=3V
15
μA
CHRG Pin Output Low Voltage
VCHRG ICHRG=5mA
0.6
V
Recharge Battery Threshold Voltage ΔVRECHRG VFLOAT-VRECHRG
100
mV
Thermal Protection Temperature
TLIM
120
°С
Soft-Start Time
tSS
IBAT=0 to 1000V/RPROG
100
μs
Recharge Comparator Filter Time
tRECHARGE VBAT High to Low
1
ms
Termination Comparator Filter Time
tTERM
1000
μs
PROG Pin Pull-Up Current
IPROG
1
μA
Notes: 1. Supply current includes PROG pin current (approximately 100μA) but does not include any current
delivered to the battery through the BAT pin (approximately 100mA).
2. ITERM is expressed as a fraction of measured full charge current with indicated PROG resistor.
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Preliminary
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OPERATION
The UTC UB2017 is a single cell lithium-ion battery charger using a constant-current/constant-voltage algorithm. It
can deliver up to 500mA of charge current (using a good thermal PCB layout) with a final float voltage accuracy of
±1.2%. The UTC UB2017 includes an internal P-channel power MOSFET and thermal regulation circuitry. No
blocking diode or external current sense resistor is required; thus, the basic charger circuit requires only two external
components. Furthermore, the UTC UB2017 is capable of operating from a USB power source.
1. Normal Charge Cycle
A charge cycle begins when the voltage at the VCC pin rises above the UVLO threshold level and a 1% program
resistor is connected from the PROG pin to ground or when a battery is connected to the charger output. If the BAT
pin is less than 2.9V, the charger enters trickle charge mode. In this mode, the UTC UB2017 supplies approximately
1/10 the programmed charge current to bring the battery voltage up to a safe level for full current charging. When the
BAT pin voltage rises above 2.9V, the charger enters constant-current mode, where the programmed charge current
is supplied to the battery. When the BAT pin approaches the final float voltage (4.2V), the UTC UB2017 enters
constant-voltage mode and the charge current begins to decrease. The charge cycle ends when the charge current
drops to 1/10 of the programmed value.
2. Programming Charge Current
The charge current is programmed using a single resistor from the PROG pin to ground. The battery charge
current is 1060 times the current out of the PROG pin. The program resistor and the charge current are calculated
using the following equations:
1000V
1000 V
R PROG =
, ICHG =
ICHG
R PROG
The charge current out of the BAT pin can be determined at any time by monitoring the PROG pin voltage using
the following equation:
V
IBAT = PROG × 1000
R PROG
This actual current will vary from IC to IC. The typical variation is within ±20%.
3. Charge Termination
A charge cycle is terminated when the charge current falls to 1/10th the programmed value after the final float
voltage is reached. This condition is detected by using an internal, filtered comparator to monitor the PROG pin.
When the PROG pin voltage falls below 100mV for longer than tTERM (typically 1ms), charging is terminated. The
charge current is latched off and the UTC UB2017 enters standby mode, where the input supply current drops to
200mA. (Note: C/10 termination is disabled in trickle charging and thermal limiting modes).
When charging, transient loads on the BAT pin can cause the PROG pin to fall below 100mV for short periods of
time before the DC charge current has dropped to 1/10th the programmed value. The 1ms filter time (tTERM) on the
termination comparator ensures that transient loads of this nature do not result in premature charge cycle
termination. Once the average charge current drops below 1/10th the programmed value, the UTC UB2017
terminates the charge cycle and ceases to provide any current through the BAT pin. In this state, all loads on the
BAT pin must be supplied by the battery. The UTC UB2017 constantly monitors the BAT pin voltage in standby
mode. If this voltage drops below the 4.1V recharge threshold (VRECHRG), another charge cycle begins and current is
once again supplied to the battery. To manually restart a charge cycle in standby mode, the input voltage must be
removed and reapplied, or the charger must be shut down and restarted using the PROG pin.
4. Charge Status Indicator (CHRG)
The charge status output has three different states: strong pull-down (~10mA), weak pull-down (~20μA) and high
impedance. The strong pull-down state indicates that the UTC UB2017 is in a charge cycle. Once the charge cycle
has terminated, the pin state is determined by undervoltage lockout conditions. A weak pull-down indicates that VCC
meets the UVLO conditions and the UTC UB2017 is ready to charge. High impedance indicates that the UTC
UB2017 is in undervoltage lockout mode: either VCC is less than 100mV above the BAT pin voltage or insufficient
voltage is applied to the VCC pin.
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Preliminary
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OPERATION(Cont.)
5. Thermal Limiting
An internal thermal feedback loop reduces the programmed charge current if the die temperature attempts to rise
above a preset value of approximately 120°С. This feature protects the UTC UB2017 from excessive temperature
and allows the user to push the limits of the power handling capability of a given circuit board without risk of
damaging the UTC UB2017. The charge current can be set according to typical (not worst-case) ambient
temperature with the assurance that the charger will automatically reduce the current in worst-case conditions.
6. Undervoltage Lockout (UVLO)
An internal undervoltage lockout circuit monitors the input voltage and keeps the charger in shutdown mode until
VCC rises above the undervoltage lockout threshold. The UVLO circuit has a built-in hysteresis of 120mV.
Furthermore, to protect against reverse current in the power MOSFET, the UVLO circuit keeps the charger in
shutdown mode if VCC falls to within 30mV of the battery voltage. If the UVLO comparator is tripped, the charger will
not come out of shutdown mode until VCC rise 100mV above the battery voltage.
„
APPLICATION INFORMATION
Stability Considerations
The constant-voltage mode feedback loop is stable without an output capacitor provided a battery is connected to
the charger output. With no battery present, an output capacitor is recommended to reduce ripple voltage. When
using high value, low ESR ceramic capacitors, it is recommended to add a 1W resistor in series with the capacitor.
No series resistor is needed if tantalum capacitors are used. In constant-current mode, the PROG pin is in the
feedback loop, not the battery. The constant-current mode stability is affected by the impedance at the PROG pin.
With no additional capacitance on the PROG pin, the charger is stable with program resistor values as high as 20kΩ.
However, additional capacitance on this node reduces the maximum allowed program resistor thus it should be
avoided. Average, rather than instantaneous, charge current may be of interest to the user. For example, if a
switching power supply operating in low current mode is connected in parallel with the battery, the average current
being pulled out of the BAT pin is typically of more interest than the instantaneous current pulses. In such a case, a
simple RC filter can be used on the PROG pin to measure the average battery current as shown in Figure 1. A 10kΩ
resistor has been added between the PROG pin and the filter capacitor to ensure stability.
Fig. 1 Isolating Capacitive Load on PROG Pin
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Preliminary
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APPLICATION INFORMATION(Cont.)
Thermal Limiting
An internal thermal feedback loop reduces the programmed charge current if the die temperature attempts to rise
above a preset value of approximately 120°C. This feature protects the UTC UB2017 from excessive temperature
and allows the user to push the limits of the power handling capability of a given circuit board without risk of
damaging the UTC UB2017. The charge current can be set according to typical (not worst-case) ambient
temperature with the assurance that the charger will automatically reduce the current in worst-case conditions.
The conditions that cause the UTC UB2017 to reduce charge current through thermal feedback can be
approximated by considering the power dissipated in the IC. Nearly all of this power dissipation is generated by the
internal MOSFET. This is calculated to be approximately:
PD = (VCC − VBAT ) × IBAT
Where PD is the power dissipated, VCC is the input supply voltage, VBAT is the battery voltage and IBAT is the
charge current. The approximate ambient temperature at which the thermal feedback begins to protect the IC is:
TA = 120 o C − PD × θ JA
TA = 120 o C − (VCC − VBAT ) × IBAT × θ JA
Moreover, when thermal feedback reduces the charge current, the voltage at the PROG pin is also reduced
proportionally as discussed in the Operation section. It is important to remember that UTC UB2017 applications do
not need to be designed for worst-case thermal conditions since the IC will automatically reduce power dissipation
when the junction temperature reaches approximately 120°C.
Thermal Considerations
Because of the small size of the Thin SOT package, it is very important to use a good thermal PC board layout to
maximize the available charge current. The thermal path for the heat generated by the IC is from the die to the
copper lead frame, through the package leads, (especially the ground lead) to the PC board copper. The PC board
copper is the heat sink. The footprint copper pads should be as wide as possible and expand out to larger copper
areas to spread and dissipate the heat to the surrounding ambient. Feed-through vias to inner or backside copper
layers are also useful in improving the overall thermal performance of the charger. Other heat sources on the board,
not related to the charger, must also be considered when designing a PC board layout because they will affect
overall temperature rise and the maximum charge current. The following table lists thermal resistance for several
different board sizes and copper areas. All measurements were taken in still air on 3/32" FR-4 board with the device
mounted on topside.
Table 1 Measured Thermal Resistance on 2-Layer Board (Note 1)
COPPER AREA
THERMAL RESISTANCE (θJA)
BOARD AREA
JUNCTION-TO-AMBIENT
TOPSIDE
BACKSIDE
2500mm2
2500mm2
2500mm2
125°C/W
1000mm2
2500mm2
2500mm2
125°C/W
2
2
2
225mm
2500mm
2500mm
130°C/W
100mm2
2500mm2
2500mm2
135°C/W
50mm2
2500mm2
2500mm2
150°C/W
Note: 1. Each layer uses one ounce copper
Table 2 Measured Thermal Resistance on 4-Layer Board (Note 1)
THERMAL RESISTANCE (θJA)
COPPER AREA (EACH SIDE)
BOARD AREA
JUNCTION-TO-AMBIENT
2500mm2 (Note 2)
2500mm2
80°C/W
Notes: 1. Top and bottom layers use two ounce copper, inner layer use one ounce copper
2. 10,000mm2 total copper area
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Preliminary
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APPLICATION INFORMATION(Cont.)
Increasing Thermal Regulation Current
Reducing the voltage drop across the internal MOSFET can significantly decrease the power dissipation in the IC.
This has the effect of increasing the current delivered to the battery during thermal regulation. One method is by
dissipating some of the power through an external component, such as a resistor or diode. While this application
delivers more energy to the battery and reduces charge time in thermal mode, it may actually lengthen charge time
in voltage mode if VCC becomes low enough to put the UTC UB2017 into dropout. Figure 2 shows how this circuit
can result in dropout as RCC becomes large. This technique works best when RCC values are minimized to keep
component size small and avoid dropout. Remember to choose a resistor with adequate power handling capability.
5V
RCC
VCC
BAT
UTC
UB2017
1µF
PROG
GND
+
Li-Ion
BATTERY
2kΩ
Fig. 2 A Circuit to Maximize Thermal Mode Charge Current
VCC Bypass Capacitor
Many types of capacitors can be used for input bypassing. However, caution must be exercised when using
multilayer ceramic capacitors. Because of the self-resonant and high Q characteristics of some types of ceramic
capacitors, high voltage transients can be generated under some start-up conditions, such as connecting the charger
input to a live power source. Adding a 1 W resistor in series with an X5R ceramic capacitor will minimize start-up
voltage transients.
Charge Current Soft-Start
The UTC UB2017 includes a soft-start circuit to minimize the inrush current at the start of a charge cycle. When a
charge cycle is initiated, the charge current ramps from zero to the full-scale current over a period of approximately
50ms. This has the effect of minimizing the transient current load on the power supply during start-up.
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Preliminary
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APPLICATION INFORMATION(Cont.)
CHRG Status Output Pin
The CHRG pin can provide an indication that the input voltage is greater than the undervoltage lockout threshold
level. A weak pull-down current of approximately 20mA indicates that sufficient voltage is applied to VCC to begin
charging. When a discharged battery is connected to the charger, the constant current portion of the charge cycle
begins and the CHRG pin pulls to ground. The CHRG pin can sink up to 10mA to drive an LED that indicates that a
charge cycle is in progress. When the battery is nearing full charge, the charger enters the constant-voltage portion
of the charge cycle and the charge current begins to drop. When the charge current drops below 1/10 of the
programmed current, the charge cycle ends and the strong pull-down is replaced by the 20mA pull-down, indicating
that the charge cycle has ended. If the input voltage is removed or drops below the undervoltage lockout threshold,
the CHRG pin becomes high impedance. Figure 3 shows that by using two different value pull-up resistors, a
microprocessor can detect all three states from this pin. To detect when the UTC UB2017 is in charge mode, force
the digital output pin (OUT) high and measure the voltage at the CHRG pin. The N-channel MOSFET will pull the pin
voltage low even with the 2kΩ pull-up resistor. Once the charge cycle terminates, the N-channel MOSFET is turned
off and a 20mA current source is connected to the CHRG pin. The IN pin will then be pulled high by the 2kΩ pull-up
resistor. To determine if there is a weak pull-down current, the OUT pin should be forced to a high impedance state.
The weak current source will pull the IN pin low through the 800kΩ resistor; if CHRG is high impedance, the IN pin
will be pulled high, indicating that the part is in a UVLO state.
Fig. 3 Using a Microprocessor to Determine CHRG State
Reverse Polarity Input Voltage Protection
In some applications, protection from reverse polarity voltage on VCC is desired. If the supply voltage is high
enough, a series blocking diode can be used. In other cases, where the voltage drop must be kept low a P-channel
MOSFET can be used.
Fig. 4 Low Loss Input Reverse Polarity Protection
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Preliminary
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APPLICATION INFORMATION(Cont.)
USB and Wall Adapter Power
The UTC UB2017 allows charging from both a wall adapter and a USB port. Figure 5 shows an example of how to
combine wall adapter and USB power inputs. A P-channel MOSFET, MP1, is used to prevent back conducting into
the USB port when a wall adapter is present and a Schottky diode, D1, is used to prevent USB power loss through
the 1kΩ pull-down resistor. Typically a wall adapter can supply more current than the 500mA-limited USB port.
Therefore, an N-channel MOSFET, MN1 and an extra 10kΩ program resistor are used to increase the charge
current to 600mA when the wall adapter is present.
Fig. 5 Combining Wall Adapter and USB Power
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Preliminary
CMOS IC
TYPICAL APPLICATION CIRCUIT
5V WALL
ADAPTER
500mA ICHG
IBAT
BAT
D1
USB POWER
400mA ICHG
VCC
MP1
+
UTC
UB2017
Li-Ion
BATTERY
2.5kΩ
PROG
GND
1µF
1kΩ
10kΩ MN1
100mA/
500mA
µC
Fig. 1 USB/Wall Adapter Power Li-Ion Charger
5V
330Ω
1µF
LED
VCC
LED
BAT
CHRG
UTC
UB2017
CHRGT
+
PROG
2kΩ
GND
MN1
Li-Ion
BATTERY
SHDN
Fig. 2 Full Featured Single Cell Li-Ion Charger
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Preliminary
CMOS IC
TYPICAL APPLICATION CIRCUIT(Cont.)
5V
0.25Ω
500mA
VCC
BAT
UTC
UB2017
1µF
PROG
GND
+
Li-Ion
BATTERY
2kΩ
Fig. 3 500mA Li-Ion Charger with External Power Dissipation
Fig. 4 Basic Li-Ion Charger with Reverse Polarity Input Protection
UTC assumes no responsibility for equipment failures that result from using products at values that
exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or
other parameters) listed in products specifications of any and all UTC products described or contained
herein. UTC products are not designed for use in life support appliances, devices or systems where
malfunction of these products can be reasonably expected to result in personal injury. Reproduction in
whole or in part is prohibited without the prior written consent of the copyright owner. The information
presented in this document does not form part of any quotation or contract, is believed to be accurate
and reliable and may be changed without notice.
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