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LTC4058-4.2/LTC4058X-4.2 Standalone Linear Li-Ion Battery Charger with Thermal Regulation in DFN
FEATURES
s s s
DESCRIPTIO
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s s s s s s s s s s s s
Programmable Charge Current Up to 950mA Complete Linear Charger in DFN Package No MOSFET, Sense Resistor or Blocking Diode Required Thermal Regulation Maximizes Charge Rate Without Risk of Overheating* Battery Kelvin Sensing Improves Charging Accuracy Charges Directly from a USB Port C/10 Charge Termination Preset 4.2V Charge Voltage with 1% Accuracy Charge Current Monitor Output for Gas Gauging* Automatic Recharge Charge Status Output "AC Present" Output 2.9V Trickle Charge Threshold (LTC4058) Available Without Trickle Charge (LTC4058X) Soft-Start Limits Inrush Current Low Profile (3mm x 3mm x 0.75mm) DFN Package
The LTC(R)4058 is a complete constant-current/constantvoltage linear charger for single cell lithium-ion batteries. Its DFN package and low external component count make the LTC4058 ideally suited for portable applications. Furthermore, the LTC4058 is designed to work within USB power specifications. The LTC4058 can Kelvin sense the battery terminal for more accurate float voltage charging. No external sense resistor or external blocking diode are required due to the internal MOSFET architecture. Thermal feedback regulates the charge current to limit the die temperature during high power operation or high ambient temperature conditions. The charge voltage is fixed at 4.2V and the charge current is programmed with a resistor. The LTC4058 terminates the charge cycle when the charge current drops to 10% of the programmed value after the final float voltage is reached. When the input supply (wall adapter or USB supply) is removed, the LTC4058 enters a low current state dropping the battery drain current to less than 2A. Other features include charge current monitor, undervoltage lockout, automatic recharge and status pins to indicate charge termination and the presence of an input voltage.
, LTC and LT are registered trademarks of Linear Technology Corporation. *US Patent 6,522,118
APPLICATIO S
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Cellular Telephones, PDAs, MP3 Players Bluetooth Applications
TYPICAL APPLICATIO
Complete Charge Cycle (750mAh Battery)
700 CONSTANT CURRENT CONSTANT VOLTAGE 4.75 4.50
BATTERY VOLTAGE (V)
Single Cell Li-Ion Battery Charger with Kelvin Sense
CHARGE CURRENT (mA) 600mA VIN 4.5V TO 6.5V VCC BAT BSENSE LTC4058-4.2 CHRG ACPR EN PROG GND
600 500 400 300 200 100
+
1-CELL Li-Ion BATTERY
1F
1.65k
405842 TA01
0
3.00 0 0.25 0.5 0.75 1.0 1.25 1.5 1.75 2.0 2.25 405842 TA02 TIME (HOURS)
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VCC = 5V JA = 40C/W RPROG = 1.65k TA = 25C
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4.25 4.00 3.75 3.50 3.25
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LTC4058-4.2/LTC4058X-4.2
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW BSENSE 1 BAT 2 CHRG 3 GND 4 9 8 7 6 5 EN ACPR VCC PROG
Input Supply Voltage (VCC) ....................... -0.3V to 10V PROG ............................................. - 0.3V to VCC + 0.3V BAT, BSENSE .............................................. -0.3V to 7V CHRG, ACPR, EN ...................................... -0.3V to 10V BAT Short-Circuit Duration .......................... Continuous BAT Pin Current ........................................................ 1A PROG Pin Current ................................................... 1mA Maximum Junction Temperature .......................... 125C Operating Temperature Range (Note 2) .. - 40C to 85C Storage Temperature Range ................. - 65C to 125C
ORDER PART NUMBER LTC4058EDD-4.2 LTC4058XEDD-4.2 DD PART MARKING LAEV LBDH
DD PACKAGE 8-LEAD (3mm x 3mm) PLASTIC DFN
TJMAX = 125C, JA = 40C/W (NOTE 3) EXPOSED PAD IS GROUND (PIN 9) MUST BE SOLDERED TO PCB
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The q denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VCC = 5V, unless otherwise noted.
SYMBOL VCC ICC PARAMETER Input Supply Voltage Input Supply Current Charge Mode (Note 4), RPROG = 10k Standby Mode (Charge Terminated) Shutdown Mode (EN = 5V, VCC < VBSENSE or VCC < VUV) 0C TA 85C, 4.3V < VCC < 6.5V RPROG = 10k, Current Mode RPROG = 2k, Current Mode Standby Mode, VBSENSE = 4.2V Shutdown Mode (EN = 5V, VCC < VBSENSE or VCC < VUV) Sleep Mode, VCC = 0V VBSENSE < VTRIKL, RPROG = 2k (Note 6) RPROG = 10k, VBSENSE Rising (Note 6) RPROG = 10k (Note 6) From VCC Low to High
q q q q q q q q
ELECTRICAL CHARACTERISTICS
CONDITIONS
q q q q
MIN 4.25
TYP 0.3 200 25
MAX 6.5 1 500 50 4.242 107 535 -6 2 2 60 3 110 3.92 300 1 5 140 50 0.115 0.115 1.07 0.6 0.6 140
UNITS V mA A A V mA mA A A A mA V mV V mV V V M mV mV mA/mA mA/mA V V V mV
VFLOAT IBAT IBSENSE
Regulated Output (Float) Voltage BAT Pin Current BSENSE Pin Current (Note 5)
4.158 93 465
4.2 100 500 -2.5 1 1
ITRIKL VTRIKL VTRHYS VUV VUVHYS VEN(IL) VEN(IH) REN VASD ITERM VPROG VCHRG VACPR VRECHRG
Trickle Charge Current Trickle Charge Threshold Voltage Trickle Charge Hysteresis Voltage VCC Undervoltage Lockout Voltage VCC Undervoltage Lockout Hysteresis EN Pin Input Low Voltage EN Pin Input High Voltage EN Pin Pull-Down Resistor VCC - VBSENSE Lockout Threshold C/10 Termination Current Threshold PROG Pin Voltage CHRG Pin Output Low Voltage ACPR Pin Output Low Voltage Recharge Battery Threshold Voltage
q
30 2.8 60 3.7 150 0.4 1.2 70 5
45 2.9 80 3.8 200 0.7 0.7 2 100 30 0.10 0.10 1 0.35 0.35
VCC from Low to High VCC from High to Low RPROG = 10k (ICHG = 100mA) (Note 7) RPROG = 2k (ICHG = 500mA) RPROG = 10k, Current Mode ICHRG = 5mA IACPR = 5mA VFLOAT - VRECHRG, 0C TA 85C
q q
0.085 0.085 0.93
60
100
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LTC4058-4.2/LTC4058X-4.2
The q denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VCC = 5V, unless otherwise noted.
SYMBOL TLIM RON tSS tRECHARGE tTERM PARAMETER Junction Temperature in Constant Temperature Mode Power FET "ON" Resistance (Between VCC and BAT) Soft-Start Time Recharge Comparator Filter Time Termination Comparator Filter Time IBAT = 0 to IBAT =1000V/RPROG VBSENSE High to Low IBAT Drops Below ICHG/10 0.75 400 CONDITIONS MIN TYP 120 600 100 2 1000 4.5 2500 MAX UNITS C m s ms s
ELECTRICAL CHARACTERISTICS
Note 1: Absolute Maximum Ratings are those values beyond which the life of the device may be impaired. Note 2: The LTC4058E-4.2/LTC4058XE-4.2 are guaranteed to meet performance specifications from 0C to 70C. Specifications over the -40C to 85C operating temperature range are assured by design, characterization and correlation with statistical process controls. Note 3: Failure to solder the exposed backside of the package to the PC board will result in a thermal resistance much higher than 40C/W.
Note 4: Supply current includes PROG pin current (approximately 100A) but does not include any current delivered to the battery through the BAT pin (approximately 100mA). Note 5: For all Li-Ion applications, the BSENSE pin must be electrically connected to the BAT pin. Note 6: This parameter is not applicable to the LTC4058X. Note 7: ITERM is expressed as a fraction of measured full charge current with indicated PROG resistor.
TYPICAL PERFOR A CE CHARACTERISTICS
PROG Pin Voltage vs Supply Voltage (Constant Current Mode)
1.015 1.010 1.005 VCC = 5V VBAT = VBSENSE = 4V TA = 25C RPROG = 10k
VPROG (V)
VPROG (V)
1.000 0.995
1.0000 0.9975 0.9950
IBAT (mA)
0.990 0.985
4
4.5
5
5.5 VCC (V)
6
UW
6.5 7
405842 G01
PROG Pin Voltage vs Temperature
1.0100 1.0075 1.0050 1.0025
400 300 200 100 0
Charge Current vs PROG Pin Voltage
600 500 VCC = 5V TA = 25C RPROG = 2k
VCC = 5V VBAT = VBSENSE = 4V RPROG = 10k
0.9925 0.9900 -50 -25 50 25 TEMPERATURE (C) 0 75 100
0
0.2
0.4
0.6 0.8 VPROG (V)
1
1.2
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405842 G03
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LTC4058-4.2/LTC4058X-4.2 TYPICAL PERFOR A CE CHARACTERISTICS
Regulated Output (Float) Voltage vs Charge Current
4.26 VCC = 5V 4.24 TA = 25C RPROG = 1.25k 4.22
VFLOAT (V) VFLOAT (V)
4.215 4.210 4.205 4.200 4.195 4.190 4.185 -50
4.18 4.16 4.14 4.12 4.10 0 100 200 300 400 IBAT (mA) 500 600 700
VFLOAT (V)
4.20
CHRG Pin I-V Curve (Pull-Down State)
30 TA = -40C 25 20 TA = 25C 30
ICHRG (mA)
IACPR (mA)
15 10 5 0 0 1 2 4 3 VCHRG (V) 5 6 7
15 10 5 0 0 1 2 4 3 VACPR (V) 5 6 7
ITRKL (mA)
TA = 90C
VCC = 5V VBAT = VBSENSE = 4V
Trickle Charge Current vs Supply Voltage
60 50 RPROG = 2k 40 ITRKL (mA) VTRKL (V) 30 20 10 0 RPROG = 10k VBAT = VBSENSE = 2.5V TA = 25C
3.000 2.975 2.950
2.900 2.875 2.850 2.825
IBAT (mA)
4
4.5
5
5.5 VCC (V)
6
4
UW
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Regulated Output (Float) Voltage vs Temperature
VCC = 5V RPROG = 10k 4.215 4.210 4.205 4.200 4.195 4.190 4.185
Regulated Output (Float) Voltage vs Supply Voltage
TA = 25C RPROG = 10k
-25
0 25 50 TEMPERATURE (C)
75
100
4
4.5
5
5.5 VCC (V)
6
6.5
7
405842 G05
405842 G06
ACPR Pin I-V Curve (Pull-Down State)
60
TA = -40C 25 20 TA = 25C
Trickle Charge Current vs Temperature
VCC = 5V VBAT = VBSENSE = 2.5V RPROG = 2k
TA = 90C
50 40 30 20 10 0 -50 RPROG = 10k
VCC = 5V VBAT = VBSENSE = 4V
-25
0 25 50 TEMPERATURE (C)
75
100
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Trickle Charge Threshold Voltage vs Temperature
VCC = 5V RPROG = 10k 600 500 400 300 200 100
Charge Current vs Battery Voltage
2.925
6.5
7
2.800 -50
-25
50 25 TEMPERATURE (C)
0
75
100
0 2.4
VCC = 5V JA = 40C/W RPROG = 2k 2.7 3 3.3 3.6 VBAT (V) 3.9 4.2 4.5
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LTC4058-4.2/LTC4058X-4.2 TYPICAL PERFOR A CE CHARACTERISTICS
Charge Current vs Supply Voltage
600 500 400
IBAT (mA)
RPROG = 2k
500
300 200 100 0
VBAT = VBSENSE = 4V TA = 25C JA = 40C/W
300 200
VCC = 5V VBAT = VBSENSE = 4V JA = 40C/W
VRECHRG (V)
IBAT (mA)
RPROG = 10k
4
4.5
5
5.5 VCC (V)
6
Power FET Transistor Curve
800 700 600
800
VCC = 5V VBSENSE = 3.5V TA = 25C RPROG = 2k
RDS(ON) (m)
IBAT (mA)
500 400 300 200
100 0 3.8 4.1 4.4 4.7 VBAT (V) 5 5.3
405842 G16
PI FU CTIO S
BSENSE (Pin 1): Battery Sense. This pin is used to Kelvin sense the positive battery terminal and regulate the final float voltage to 4.2V. An internal precision resistor divider sets this float voltage and is disconnected in shutdown mode. For Li-Ion applications, this pin must be electrically connected to BAT. BAT (Pin 2): Charge Current Output. Provides charge current to the battery from the internal P-channel MOSFET. CHRG (Pin 3): Charge Status Open-Drain Output. When the battery is charging, the CHRG pin is pulled low by an internal N-channel MOSFET. When the charge cycle is completed, CHRG becomes high impedance. GND (Pins 4, 9): Ground/Exposed Pad. The exposed backside of the package (Pin 9) is also ground and must be soldered to the PC board for maximum heat transfer. PROG (Pin 5): Charge Current Program and Charge Current Monitor. Charge current is programmed by connecting a 1% resistor, RPROG, to ground. When charging in constant-current mode, this pin servos to 1V. In all modes,
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6.5 7
405842 G13
Charge Current vs Ambient Temperature
600 ONSET OF THERMAL REGULATION
Recharge Threshold Voltage vs Temperature
4.16 4.14 VCC = 5V RPROG = 10k
RPROG = 2k 400
4.12 4.10 4.08
RPROG = 10k
100 0 -50
4.06 4.04 -50
-25
50 25 75 0 TEMPERATURE (C)
100
125
-25
0 25 50 TEMPERATURE (C)
75
100
405842 G14
405842 G15
Power FET "ON" Resistance vs Temperature
VCC = 5V VBAT = 4.8V = 4V V 700 RBSENSE 2k PROG = 600
500
400
300 -50
-25
0 25 50 TEMPERATURE (C)
75
100
405842 G17
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LTC4058-4.2/LTC4058X-4.2
PI FU CTIO S
the voltage on this pin can be used to measure the charge current using the following formula: IBAT = (VPROG/RPROG) * 1000 This pin is clamped to approximately 2.4V. Driving this pin to voltages beyond the clamp voltage can draw currents as high as 1.5mA. VCC (Pin 6): Positive Input Supply Voltage. Provides power to the charger. VCC can range from 4.25V to 6.5V. This pin should be bypassed with at least a 1F capacitor. When VCC is within 100mV of the BSENSE pin voltage, the LTC4058 enters shutdown mode dropping the battery drain current to less than 2A. ACPR (Pin 7): Power Supply Status Open-Drain Output. When VCC is greater than the undervoltage lockout threshold and at least 100mV above VBSENSE, the ACPR pin is pulled to ground; otherwise, the pin is high impedance. EN (Pin 8): Enable Input . A logic high on the EN pin will put the LTC4058 into shutdown mode where the battery drain current is reduced to less than 2A and the supply current is reduced to less than 50A. A logic low or floating the EN pin (allowing an internal 2M pull-down resistor to pull this pin low) enables charging.
BLOCK DIAGRA
MA
ACPR 7 VA
CHRG 3
CA
-
+
R3 1V
CHARGE ACPR R4 LOGIC TERM C1
+ -
0.1V R5
EN EN 8 REN
SHDN TRICKLE CHARGE DISABLED ON THE LTC4058X
C2
-
2.9V
+
TO BAT 5 RPROG PROG GND 4, 9
6
+
-
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6 VCC 120C TA TDIE 1x 1000x BAT 5A BSENSE R1
2 1
+
R2
-
REF 1.21V
405842 BD
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LTC4058-4.2/LTC4058X-4.2
OPERATIO
The LTC4058 is a single cell lithium-ion battery charger using a constant-current/constant-voltage algorithm. It can deliver up to 950mA of charge current (using a good thermal PCB layout) with a final float voltage accuracy of 1%. The LTC4058 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 LTC4058 is capable of operating from a USB power source. 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. If the BSENSE pin is less than 2.9V, the charger enters trickle charge mode. In this mode, the LTC4058 supplies approximately 1/10th the programmed charge current to bring the battery voltage up to a safe level for full current charging. (Note: The LTC4058X does not include this trickle charge feature.) When the BSENSE pin voltage rises above 2.9V, the charger enters constant-current mode where the programmed charge current is supplied to the battery. When the BSENSE pin approaches the final float voltage (4.2V), the LTC4058 enters constant-voltage mode and the charge current begins to decrease. When the charge current drops to 1/10th of the programmed value, the charge cycle ends. Programming Charge Current The charge current is programmed using a single resistor from the PROG pin to ground. The charge current out of the BAT pin is 1000 times the current out of the PROG pin. The program resistor and the charge current are calculated using the following equations:
RPROG =
1000 V 1000 V , I CHG = ICHG RPROG
Charge current out of the BAT pin can be determined at any time by monitoring the PROG pin voltage and using the following equation:
IBAT =
VPROG * 1000 RPROG
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Charge Termination The charge cycle terminates when the charge current falls to 10% 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 100mV1 for longer than tTERM (typically 1ms), charging is terminated. The charge current is latched off and the LTC4058 enters standby mode where the input supply current drops to 200A. (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 10% of 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 10% of the programmed value, the LTC4058 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 LTC4058 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 charge current is once again supplied to the battery. To manually restart a charge cycle when in standby mode, the input voltage must be removed and reapplied or the charger must be shut down and restarted using the EN pin. Figure 1 shows the state diagram of a typical charge cycle. Charge Status Indicator (CHRG) The charge status output has two states: pull-down and high impedance. The pull-down state indicates that the LTC4058 is in a charge cycle. Once the charge cycle has terminated or the LTC4058 is disabled, the pin state becomes high impedance.
1Any external sources that hold the PROG pin above 100mV will prevent the LTC4058 from terminating a charge cycle.
7
LTC4058-4.2/LTC4058X-4.2
OPERATIO
POWER ON EN DRIVEN LOW OR UVLO CONDITION STOPS
SHUTDOWN MODE ICC DROPS TO <25A CHRG: Hi-Z
EN DRIVEN HIGH OR UVLO CONDITION
Figure 1. State Diagram of a Typical Charge Cycle
Power Supply Status Indicator (ACPR) The power supply status output has two states: pull-down and high impedance. The pull-down state indicates that VCC is above the UVLO threshold (3.8V) and is also 100mV above the battery voltage. When these conditions are not met, the ACPR pin is high impedance indicating that the LTC4058 is unable to charge the battery. 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 120C. This feature protects the LTC4058 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 LTC4058. The charge current can be set according to typical (not worst case) ambient temperature with the assurance that the
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BSENSE < 2.9V TRICKLE CHARGE MODE 1/10TH FULL CURRENT CHRG: STRONG PULL-DOWN BSENSE > 2.9V CHARGE MODE FULL CURRENT CHRG: STRONG PULL-DOWN PROG < 100mV STANDBY MODE NO CHARGE CURRENT CHRG: Hi-Z
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charger will automatically reduce the current in worst-case conditions. DFN power considerations are discussed further in the Applications Information section. 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 200mV. 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 BSENSE voltage. If the UVLO comparator is tripped, the charger will not come out of shutdown mode until VCC rises 100mV above the BSENSE voltage. Manual Shutdown At any point in the charge cycle, the LTC4058 can be put into shutdown mode by driving the EN pin high. This reduces the battery drain current to less than 2A and the supply current to less than 50A. When in shutdown mode, the CHRG pin is in the high impedance state. A new charge cycle can be initiated by driving the EN pin low. A resistor pull-down on this pin forces the LTC4058 to be enabled if the pin is allowed to float. Automatic Recharge Once the charge cycle is terminated, the LTC4058 continuously monitors the voltage on the BSENSE pin using a comparator with a 2ms filter time (tRECHARGE). A charge cycle restarts when the battery voltage falls below 4.10V (which corresponds to approximately 80% to 90% battery capacity). This ensures that the battery is kept at, or near, a fully charged condition and eliminates the need for periodic charge cycle initiations. The CHRG output enters a pull-down state during recharge cycles.
BSENSE > 2.9V
2.9V < BSENSE < 4.1V
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LTC4058-4.2/LTC4058X-4.2
APPLICATIO S I FOR ATIO
Kelvin Sensing the Battery (BSENSE Pin)
The internal P-channel MOSFET drain is connected to the BAT pin, while the BSENSE pin connects through an internal precision resistor divider to the input of the constantvoltage amplifier. This architecture allows the BSENSE pin to Kelvin sense the positive battery terminal. This is especially useful when the copper trace from the BAT pin to the Li-Ion battery is long and has a high resistance. High charge currents can cause a significant voltage drop between the positive battery terminal and the BAT pin. In this situation, a separate trace from the BSENSE pin to the battery terminals will eliminate this voltage error and result in more accurate battery voltage sensing. The BSENSE pin MUST be electrically connected to the BAT pin. 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 on the BAT pin is recommended to reduce ripple voltage. When using high value, low ESR ceramic capacitors, it is recommended to add a 1 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 20k; however, additional capacitance on this node reduces the maximum allowed program resistor. The pole frequency at the PROG pin should be kept above 100kHz. Therefore, if the PROG pin is loaded with a capacitance, CPROG, the following equation can be used to calculate the maximum resistance value for RPROG: RPROG 1 2 * 105 * CPROG
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
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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 2. A 10k resistor has been added between the PROG pin and the filter capacitor to ensure stability.
LTC4058-4.2 PROG GND RPROG CFILTER
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10k
CHARGE CURRENT MONITOR CIRCUITRY
Figure 2. Isolating Capacitive Load on PROG Pin and Filtering
Power Dissipation It is not necessary to design for worst-case power dissipation scenarios because the LTC4058 automatically reduces the charge current during high power conditions. The conditions that cause the LTC4058 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 = 120C - PDJA TA = 120C - (VCC - VBAT) * IBAT * JA Example: An LTC4058 operating from a 5V supply is programmed to supply 800mA full-scale current to a discharged Li-Ion battery with a voltage of 3.3V. Assuming JA is 50C/W (see Thermal Considerations), the ambient temperature at which the LTC4058 will begin to reduce the charge current is approximately: TA = 120C - (5V - 3.3V) * (800mA) * 50C/W TA = 120C - 1.36W * 50C/W = 120C - 68C TA = 52C
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LTC4058-4.2/LTC4058X-4.2
APPLICATIO S I FOR ATIO
The LTC4058 can be used above 52C ambient but the charge current will be reduced from 800mA. The approximate current at a given ambient temperature can be approximated by:
IBAT =
120C - TA ( VCC - VBAT ) * JA
Using the previous example with an ambient temperature of 60C, the charge current will be reduced to approximately:
IBAT 120C - 60C 60C = = (5V - 3.3V) * 50C/W 85C/A
IBAT = 706mA
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 LTC4058 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 120C. Thermal Considerations In order to deliver maximum charge current under all conditions, it is critical that the exposed metal pad on the backside of the LTC4058 package is soldered to the PC board ground. Correctly soldered to a 2500mm2 doublesided 1oz copper board, the LTC4058 has a thermal resistance of approximately 40C/W. Failure to make thermal contact between the exposed pad on the backside of the package and the copper board will result in thermal resistances far greater than 40C/W. As an example, a correctly soldered LTC4058 can deliver over 800mA to a battery from a 5V supply at room temperature. Without a backside thermal connection, this number will drop considerably. VCC Bypass Capacitor Many types of capacitors can be used for input bypassing, however, caution must be exercised when using multilayer
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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 1.5 resistor in series with an X5R ceramic capacitor will minimize start-up voltage transients. For more information, see Application Note 88. Charge Current Soft-Start The LTC4058 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 100s. This has the effect of minimizing the transient current load on the power supply during start-up. USB and Wall Adapter Power The LTC4058 allows charging from both a wall adapter and a USB port. Figure 3 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 1k 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 3.3k program resistor are used to increase the charge current to 800mA when the wall adapter is present.
5V WALL ADAPTER 800mA ICHG USB POWER 500mA ICHG D1 MP1 LTC4058-4.2 2 BAT 1 6 VCC BSENSE 5 4, 9 GND PROG 3.3k 1k MN1 2k
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ICHG
SYSTEM LOAD
+
Li-Ion BATTERY
Figure 3. Combining Wall Adapter and USB Power
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LTC4058-4.2/LTC4058X-4.2
APPLICATIO S I FOR ATIO
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 (as shown in Figure 4).
PACKAGE DESCRIPTIO
DD Package 8-Lead Plastic DFN (3mm x 3mm)
(Reference LTC DWG # 05-08-1698)
3.5 0.05 1.65 0.05 2.15 0.05 (2 SIDES) PACKAGE OUTLINE 0.28 0.05 0.50 BSC 2.38 0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS R = 0.115 TYP 5 0.38 0.10 8
PIN 1 TOP MARK
(DD8) DFN 0203
0.200 REF
NOTE: 1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-1) 2. ALL DIMENSIONS ARE IN MILLIMETERS 3. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 4. EXPOSED PAD SHALL BE SOLDER PLATED
Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
U
DRAIN-BULK DIODE OF FET VIN LTC4058 VCC
405842 F04
U
W
UU
Figure 4. Low Loss Input Reverse Polarity Protection
0.675 0.05
3.00 0.10 (4 SIDES)
1.65 0.10 (2 SIDES)
0.75 0.05
4 0.28 0.05 2.38 0.10 (2 SIDES)
1 0.50 BSC
0.00 - 0.05
BOTTOM VIEW--EXPOSED PAD
sn405842 405842fs
11
LTC4058-4.2/LTC4058X-4.2
TYPICAL APPLICATIO S
Full Featured Single Cell Li-Ion Charger
VIN 5V 1k 1k 6 500mA
4.7F
VCC 2 7 ACPR BAT 1 3 CHRG BSENSE LTC4058-4.2 8 5 EN PROG GND 4, 9
5V WALL ADAPTER USB POWER 1k 6 1F
RELATED PARTS
PART NUMBER LTC1732 LTC1733 LTC1734 LTC1734L LTC1998 LTC4007 LTC4050 LTC4052 LTC4053 LTC4054 LTC4057 LTC4410 DESCRIPTION Lithium-Ion Linear Battery Charger Controller Monolithic Lithium-Ion Linear Battery Charger Lithium-Ion Linear Battery Charger in ThinSOT Lithium-Ion Low Battery Detector 4A Multicell Li-Ion Battery Charger Lithium-Ion Linear Battery Charger Controller Monolithic Lithium-Ion Battery Pulse Charger USB Compatible Monolithic Li-Ion Battery Charger Standalone Linear Li-Ion Battery Charger with Integrated Pass Transistor in ThinSOT Li-Ion Linear Battery Charger USB Power Manager
TM
Lithium-Ion Linear Battery Charger in ThinSOT
LTC4412
Low Loss PowerPathTM Controller in ThinSOT
ThinSOT and PowerPath are trademarks of Linear Technology Corporation.
sn405842 405842fs
12
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 q FAX: (408) 434-0507
q
U
Li-Ion Battery Charger with Reverse Polarity Input Protection
5V WALL ADAPTER
6 VCC 500mA 2 BAT 1 BSENSE LTC4058-4.2 8 5 EN PROG GND 4, 9
405842 TA04
+
2k
1-CELL Li-Ion BATTERY 1F
405842 TA03
4.7F
+
2k
1-CELL Li-Ion BATTERY
USB/Wall Adapter Power Li-Ion Charger
2 BAT 1 BSENSE LTC4058-4.2 VCC 5 PROG GND 4, 9 10k 2.5k 100mA/ 500mA C
405842 TA05
IBAT
+
Li-Ion CELL
COMMENTS Simple Charger uses External FET, Features Preset Voltages, C/10 Charger Detection and Programmable Timer, Input Power Good Indication Standalone Charger with Programmable Timer, Up to 1.5A Charge Current Simple ThinSOT Charger, No Blocking Diode, No Sense Resistor Needed Low Current Version of LTC1734; 50mA ICHRG 180mA 1% Accurate 2.5A Quiescent Current, SOT-23 Standalone Charger, 6V VIN 28V, Up to 96% Efficiency, 0.8% Charging Voltage Accuracy Features Preset Voltages, C/10 Charger Detection and Programmable Timer, Input Power Good Indication, Thermistor Interface No Blocking Diode or External Power FET Required, 1.5A Charge Current Standalone Charger with Programmable Timer, Up to 1.25A Charge Current Thermal Regulation Prevents Overheating, C/10 Termination, C/10 Indicator, Up to 800mA Charge Current Up to 800mA Charge Current, Thermal Regulation, ThinSOT Package For Simultaneous Operation of USB Peripheral and Battery Charging from USB Port, Keeps Current Drawn from USB Port Constant, Keeps Battery Fresh, Use with the LTC4053, LTC1733, or LTC4054 Automatic Switching Between DC Sources, Load Sharing, Replaces ORing Diodes
LT/TP 1103 1K * PRINTED IN USA
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2003

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