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LT1510/LT1510-5

Constant-Voltage/

Constant-Current Battery Charger

Figure 2. Charging Lithium Batteries (Efficiency at 1.3A > 87%)

* NiCd and NiMH batteries require charge termination circuitry (not shown in Figure 1).

TYPICAL APPLICATIONS

, LTC and LT are registered trademarks of Linear Technology Corporation.

plest, most efficient solution to fast-charge modern re-

chargeable batteries including lithium-ion (Li-Ion), nickel-

metal-hydride (NiMH)* and nickel-cadmium (NiCd)* that

require constant-current and/or constant-voltage charg-

ing. The internal switch is capable of delivering 1.5A DC

current (2A peak current). The 0.1Ω onboard current

sense resistor makes the charging current programming

very simple. One resistor (or a programming current from

a DAC) is required to set the full charging current (1.5A) to

within 5% accuracy. The LT1510 with 0.5% reference

voltage accuracy meets the critical constant-voltage charg-

ing requirement for lithium cells.

The LT1510 can charge batteries ranging from 2V to 20V.

Ground sensing of current is not required and the battery’s

negative terminal can be tied directly to ground. A saturat-

ing switch running at 200kHz (500kHz for LT1510-5) gives

high charging efficiency and small inductor size. A block-

ing diode is not required between the chip and the battery

because the chip goes into sleep mode and drains only 3µA

when the wall adaptor is unplugged. Soft start and shutdown

features are also provided. The LT1510 is available in a 16-pin

fused lead power SO package with a thermal resistance of

50°C/W, an 8-pin SO and a 16-pin PDIP.

FEATURES

■

Charges NiCd, NiMH and Lithium-Ion Batteries ––

Only One

W Resistor Is Needed to Program

Charging Current

■

High Efficiency Current Mode PWM with 1.5A

Internal Switch and Sense Resistor

■

3% Typical Charging Current Accuracy

■

Precision 0.5% Voltage Reference for Voltage

Mode Charging or Overvoltage Protection

■

Current Sensing Can Be at Either Terminal of

the Battery

■

Low Reverse Battery Drain Current: 3µA

■

Charging Current Soft Start

■

Shutdown Control

■

500kHz Version Uses Small Inductor

With switching frequency as high as 500kHz, The LT

1510

current mode PWM battery charger is the smallest, sim-

APPLICATIONS

DESCRIPTION

■

Chargers for NiCd, NiMH and Lithium Batteries

■

Step-Down Switching Regulator with Precision

Adjustable Current Limit

Figure 1. 500kHz Smallest Li-Ion Cell Phone Charger (0.8A)

SW

BOOST

GND

SENSE



PROG



BAT

6.19k

8.2V TO 20V

R3

70.6k

0.25%

R4

100k

0.25%

†



2N7002

NOTE: COMPLETE LITHIUM-ION CHARGER, NO TERMINATION REQUIRED

TOKIN OR MARCON CERAMIC SURFACE MOUNT

COILTRONICS TP3-100, 10µH, 2.2mm HEIGHT (0.8A CHARGING CURRENT)

COILTRONICS TP1 SERIES, 10µH, 1.8mm HEIGHT (<0.5A CHARGING CURRENT)

PANASONIC EEFCD1B220 

OPTIONAL, SEE APPLICATIONS INFORMATION

1510 F01

C1

0.22µF

*

10µF

L1**

10µH

LT1510-5

D1

MBRM120T3

D3

MBRM120T3

D2

MMBD914L

OVP

OUT

***



22µF

4.2V

–

0.1µF

1µF

300Ω

*

**



***

†

SW

BOOST

GND

SENSE



PROG



BAT

3.83k

11V TO 28V

R3

240k

0.25%

R4

100k

0.25%

†



VN2222

NOTE: COMPLETE LITHIUM-ION CHARGER, NO TERMINATION REQUIRED

 * TOKIN OR MARCON CERAMIC SURFACE MOUNT

** COILTRONICS CTX33-2  



†

 OPTIONAL, SEE APPLICATIONS INFORMATION

1510 F02

C1

0.22µF

*

10µF

L1**

33µH

LT1510

D1

1N5819

D3

1N5819

D2

1N914

OVP

OUT



22µF

TANT

4.2V

–

0.1µF

1µF

300Ω

Summary of content (16 pages)

PAGE 1
LT1510/LT1510-5 Constant-Voltage/ Constant-Current Battery Charger FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ Charges NiCd, NiMH and Lithium-Ion Batteries –– Only One 1/10W Resistor Is Needed to Program Charging Current High Efficiency Current Mode PWM with 1.5A Internal Switch and Sense Resistor 3% Typical Charging Current Accuracy Precision 0.
PAGE 2
LT1510/LT1510-5 U W W W ABSOLUTE MAXIMUM RATINGS Operating Ambient Temperature Range Commercial ............................................. 0°C to 70°C Extended Commercial (Note 7) ........... – 40°C to 85°C Industrial (Note 8) .............................. – 40°C to 85°C Operating Junction Temperature Range LT1510C (Note 7) ............................. – 40°C to 125°C LT1510I ............................................ – 40°C to 125°C Lead Temperature (Soldering, 10 sec)..................
PAGE 3
LT1510/LT1510-5 ELECTRICAL CHARACTERISTICS VCC = 16V, VBAT = 8V, VMAX (maximum operating VCC) = 28V, no load on any outputs, unless otherwise noted. PARAMETER CONDITIONS MIN TYP MAX UNITS Overall Minimum Input Operating Voltage Undervoltage Lockout ● 7 7.8 V Reverse Current from Battery (When VCC Is Not Connected, VSW Is Floating) VBAT ≤ 20V, 0°C ≤ TJ ≤ 70°C ● 6.
PAGE 4
LT1510/LT1510-5 ELECTRICAL CHARACTERISTICS VCC = 16V, VBAT = 8V, VMAX (maximum operating VCC) = 28V, no load on any outputs, unless otherwise noted. PARAMETER CONDITIONS MIN TYP MAX UNITS VC = 1V, IVC = ±1µA 150 250 550 µmho Current Amplifier (CA2) Transconductance Maximum VC for Switch OFF ● VC ≥ 0.6V VC < 0.45V IVC Current (Out of Pin) 0.6 V 100 3 µA mA 2.5 mho Voltage Amplifier (VA), 16-Pin Only Transconductance (Note 2) Output Current from 100µA to 500µA 0.
PAGE 5
LT1510/LT1510-5 U W TYPICAL PERFORMANCE CHARACTERISTICS Efficiency of Figure 2 Circuit 100 8 7 205 6 94 ICC (mA) 92 90 88 FREQUENCY (kHz) 96 210 VCC = 16V VCC = 15V (EXCLUDING DISSIPATION ON INPUT DIODE D3) VBAT = 8.4V 98 EFFICIENCY (%) Switching Frequency vs Temperature ICC vs Duty Cycle 5 0°C 125°C 4 25°C 3 86 200 195 190 2 84 185 1 82 80 0 0.1 0.3 0.5 0.7 0.9 IBAT (A) 1.1 1.3 1.
PAGE 6
LT1510/LT1510-5 U W TYPICAL PERFORMANCE CHARACTERISTICS Switch Current vs Boost Current vs Boost Voltage Reference Voltage vs Temperature 2.470 50 95 35 30 25 20 15 10 MAXIMUM DUTY CYCLE (%) 2.468 VBOOST = 38V 28V 18V 40 BOOST CURRENT (mA) 96 VCC = 16V REFERENCE VOLTAGE (V) 45 VBOOST vs Maximum Duty Cycle 2.466 2.464 2.462 2.460 5 0 94 93 92 91 90 89 88 87 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 SWITCH CURRENT (A) 2.
PAGE 7
LT1510/LT1510-5 W BLOCK DIAGRAM 200kHz OSCILLATOR + VCC SHUTDOWN 0.7V + – VSW BOOST S – VCC QSW R R + SW + – 1.5V SLOPE COMPENSATION PWM VBAT C1 – B1 R2 + + IPROG + GND R1 IPROG = 500µA/A 1k IBAT R3 – BAT 0VP VA CA2 + 60k RS1 + – VC SENSE IBAT CA1 VREF gm = 0.64 PROG RPROG CPROG Ω – VREF 2.465V CHARGING CURRENT IBAT = (IPROG)(2000) 1510 BD ( ) IPROG = 2.465V (2000) RPROG TEST CIRCUITS Test Circuit 1 LT1510 SENSE + – VC 60k RS1 – 1k + 0.
PAGE 8
LT1510/LT1510-5 TEST CIRCUITS Test Circuit 2 LT1510 OVP + VA – VREF PROG 10k IPROG 10k 0.47µF RPROG – + + LT1013 2.465V 1510 TC02 U OPERATIO The LT1510 is a current mode PWM step-down (buck) switcher. The battery DC charging current is programmed by a resistor RPROG (or a DAC output current) at the PROG pin (see Block Diagram). Amplifier CA1 converts the charging current through RS1 to a much lower current IPROG (500µA/A) fed into the PROG pin.
PAGE 9
LT1510/LT1510-5 U W U U APPLICATIONS INFORMATION capacity ceramic capacitor (5µF to 10µF) from Tokin or United Chemi-Con/MARCON, et al., and the old standby, aluminum electrolytic, which will require more microfarads to achieve adequate ripple rating. OS-CON can also be used. The output capacitor COUT is also assumed to absorb output switching current ripple. The general formula for capacitor current is: IRMS =  V  0.29 VBAT  1 − BAT  VCC   ( ) (L1)(f) For example, with VCC = 16V, VBAT = 8.
PAGE 10
LT1510/LT1510-5 U U W U APPLICATIONS INFORMATION where RPROG is the total resistance from PROG pin to ground. For example, 1A charging current is needed. RPROG = even this low current drain. A 47k resistor from adapter output to ground should be added if Q3 is used to ensure that the gate is pulled to ground. With divider current set at 25µA, R4 = 2.465/25µA = 100k and, (2.465V)(2000) = 4.
PAGE 11
LT1510/LT1510-5 U U W U APPLICATIONS INFORMATION of the battery, canceling part or all of the 200µA. Note that if net current is into the battery and the battery is removed, the charger output voltage will float high, to near input voltage. This could be a problem when reinserting the battery, if the resulting output capacitor/battery surge current is high enough to damage either the battery or the capacitor. If net current into the battery must be less than zero in shutdown, there are several options.
PAGE 12
LT1510/LT1510-5 U U W U APPLICATIONS INFORMATION BAT 0.18Ω INTERNAL SENSE RESISTOR LT1510 ADAPTER OUTPUT SENSE R1* 1.6k D1 1N4148 C1 0.1µF 3 2 R2 D2 560k 1N4148 R4 470k 8 – 7 LT1011 GND 3.3V OR 5V + NEGATIVE EDGE TO TIMER 4 1 R3 430k * TRIP CURRENT = R1(VBAT) (R2 + R3)(0.18Ω) 1510 F06 Figure 7. Current Comparator for Initiating Float Time-Out voltage decrease is detected as an indication of near full charge.
PAGE 13
LT1510/LT1510-5 U U W U APPLICATIONS INFORMATION Example: VIN = 15V, VBAT = 8.4V, IBAT = 1.2A; ( )( ) ( ) PDRIVER 0.045W = = 14mA VX 3.3V Total board area becomes an important factor when the area of the board drops below about 20 square inches. The graph in Figure 9 shows thermal resistance vs board area for 2-layer and 4-layer boards. Note that 4-layer boards have significantly lower thermal resistance, but both types show a rapid increase for reduced board areas.
PAGE 14
LT1510/LT1510-5 U W U U APPLICATIONS INFORMATION 90 LEAD TEMPERATURE (°C) event of an input short. The body diode of Q2 creates the necessary pumping action to keep the gate of Q1 low during normal operation (see Figure 11). NOTE: PEAK DIE TEMPERATURE WILL BE ABOUT 10°C HIGHER THAN LEAD TEMPERATURE AT 1.3A CHARGING CURRENT 80 70 2-LAYER BOARD Q1 60 VIN + 4-LAYER BOARD 50 VCC ICHRG = 1.3A VIN = 16V VBAT = 8.
PAGE 15
LT1510/LT1510-5 U U W U APPLICATIONS INFORMATION GND LT1510 D1 GND GND SW VCC2 BOOST VCC1 GND PROG OVP L1 CIN VC SENSE BAT GND GND GND GND 1510 F11 Figure 13. Critical Electrical and Thermal Path Layer U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. GN Package 16-Lead Plastic SSOP (Narrow 0.150) (LTC DWG # 05-08-1641) 0.015 ± 0.004 × 45° (0.38 ± 0.10) 0.0075 – 0.0098 (0.191 – 0.249) 0.053 – 0.069 (1.351 – 1.748) 0.004 – 0.009 (0.102 – 0.
PAGE 16
LT1510/LT1510-5 U TYPICAL APPLICATION Adjustable Voltage Regulator with Precision Adjustable Current Limit 0.22µF LT1510 1N5819 SW VCC2 VIN 18V TO 25V + 100µF VCC1 PROG BOOST RPROG 4.93k 1k 30µH 0.01µF VC GND 1N914 0.1µF OVP SENSE BAT POT 5k CURRENT LIMIT LEVEL = ( ) 2.465V (2000) RPROG + 500µF POT 100k VOUT 2.5V TO 15V CURRENT LIMIT LEVEL 50mA TO 1A 1µF 1k 1510 TA01 U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted.