Datasheet LT1505, LT1505CG-1 Datasheet (Linear Technology)

High Efficiency Battery Charger

FEATURES

■

Simple Charging of Li-Ion, NiMH and NiCd Batteries

■

Very High Efficiency: Up to 97%

■

Precision 0.5% Charging Voltage Accuracy

■

Preset Battery Voltages: 12.3V, 12.6V,

16.4V and 16.8V

■

5% Charging Current Accuracy

■

Charging Current Programmed by Resistor or DAC

■

0.5V Dropout Voltage, Duty Cycle > 99.5%

■

AC Adapter Current Limit* Maximizes Charging Rate

■

Flag Indicates Li-Ion Charge Completion

■

Auto Shutdown with Adapter Removal

■

Only 10µA Battery Drain When Idle

■

Synchronizable Up to 280kHz

U

APPLICATIO S

■

Notebook Computers

■

Portable Instruments

■

Chargers for Li-Ion, NiMH, NiCd and Lead Acid
Rechargeable Batteries

LT1505

Constant-Current/Voltage

U

DESCRIPTIO

The LT®1505 PWM battery charger controller fast charges
multiple battery chemistries including lithium-ion (Li-Ion),
nickel-metal-hydride (NiMH) and nickel-cadmium (NiCd)
using constant-current or constant-voltage control. Maxi­mum current can be easily programmed by resistors or a
DAC. The constant-voltage output can be selected for 3 or 4
series Li-Ion cells with 0.5% accuracy.

A third control loop limits the current drawn from the AC
adapter during charging*. This allows simultaneous opera­tion of the equipment and fast battery charging without over­loading the AC adapter.

The LT1505 can charge batteries ranging from 2.5V to 20V
with dropout voltage as low as 0.5V. Synchronous
N-channel FETs switching at 200kHz give high efficiency
and allow small inductor size. A diode is not required in
series with the battery because the charger automatically
enters a 10µA sleep mode when the wall adapter is un-
plugged. A logic output indicates Li-Ion full charge when
current drops to 20% of the programmed value.

The LT1505 is available in a 28-pin SSOP package.

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

*US Patent No. 5,723,970

TYPICAL APPLICATION

SYSTEM POWER

R

S4

0.025Ω

C1

R7

1µF

C6

0.1µF

TO

C

IN

47µF
35V

R1
1k

C7

0.68µF

(FROM

ADAPTER)

V

IN

R5

4k

R6

4k

*BODY DIODE
POLARITY MUST
BE AS SHOWN

Si4435

DBODY*

100k

M3

500Ω

U

C4

D3

0.1µF

MMSD4148T1

BOOST BOOSTC

V

CC

CLN
CLP

INFET
UV
SYNC
SHDN
FLAG
CAP
COMP1

BAT2 BAT SENSE

LT1505

GBIAS
TGATE

BGATE

PROG

3 CELL

4.2V

4.1V
AGND
PGND

SPIN

SW

V

C

V

FB

Figure 1. Low Dropout 4A Lithium-Ion Battery Charger

C

PROG

R

PROG

4.93k
1%

C3

2.2µF

300Ω

1µF

5Ω

D2

MMSD4148T1

M1
Si4412

M2
Si4412

R

X4

3k

0.33µF

NOTE: DBODY IS THE BODY DIODE OF M3
C

: SANYO OS-CON

IN

L1: SUMIDA CDRH127-150
(CAN BE FROM 10µH TO 30µH)

D4
MBRS140

C2

0.68µF

L1

15µH

R

S1

0.025Ω

R

S2

200Ω
1%

R

S3

200Ω
1%

C

OUT

22µF
25V
×2

1505 F01

V

BAT

12.6V
BATTERY

1

LT1505

WW

W

ABSOLUTE MAXIMUM RATINGS

U

(Note 1)

VCC, CLP, CLN, INFET, UV, 3CELL, FLAG................ 27V

SW Voltage with Respect to GND ........................... –2V

BOOST, BOOSTC Voltage with Respect to VCC....... 10V

GBIAS ..................................................................... 10V

SYNC, BAT2, BAT, SENSE, SPIN ............................ 20V

VC, PROG, VFB, 4.1V, 4.2V........................................ 7V

CAP, SHDN .......................................................... ±3mA

U

W

U

PACKAGE/ORDER INFORMATION

1

BOOST

2

TGATE

3

SW

4

SYNC

5

SHDN

6

AGND

7

UV

8

INFET

9

CLP

10

CLN

11

COMP1

12

CAP

13

FLAG

14

4.1V

28-LEAD PLASTIC SSOP

T

JMAX

TOP VIEW

PGND

28

BGATE

27

GBIAS

26

BOOSTC

25

V

24

BAT

23

SPIN

22

SENSE

21

BAT2

20

PROG

19

V

18

V

17

3CELL

16

4.2V

15

G PACKAGE

= 125°C, θJA = 100°C/W

CC

C

FB

ORDER PART

NUMBER

LT1505CG

TGATE, BGATE Current Continuous ....................... 0.2A

TGATE, BGATE Output Energy (per cycle) ............... 2µJ

Maximum Operating VCC......................................... 24V

Operating Ambient Temperature Range....... 0°C to 70°C

Operating Junction Temperature Range .... 0°C to 125°C

Storage Temperature Range ................. –65°C to 150°C

Lead Temperature (Soldering, 10 sec)..................300°C

1

BOOST

2

TGATE

3

SW

4

SYNC

5

SHDN

6

AGND

7

UV

8

INFET

9

NC

10

NC

11

GND

12

CAP

13

FLAG

14

4.1V

28-LEAD PLASTIC SSOP

T

= 125°C, θJA = 100°C/W

JMAX

TOP VIEW

G PACKAGE

28
27
26
25
24
23
22
21
20
19
18
17
16
15

PGND
BGATE
GBIAS
BOOSTC
V

CC

BAT
SPIN
SENSE
BAT2
PROG
V

C

V

FB

3CELL

4.2V

ORDER PART

NUMBER

LT1505CG-1

NOTE: LT1505CG-1 DOES NOT
HAVE INPUT CURRENT
LIMITING FUNCTION.

Consult factory for Industrial and Military grade parts.

ELECTRICAL CHARACTERISTICS

temperature range, otherwise specifications are at TA = 25°C. VCC = 18V, V

The ● denotes specifications which apply over the full operating

= 12.6V, V

BAT

= VCC (LT1505), no load on any

CLN

outputs unless otherwise noted.

PARAMETER CONDITIONS MIN TYP MAX UNITS
Overall

Supply Current VCC ≤ 24V ● 12 15 mA
Sense Amplifier CA1 Gain and Input Offset Voltage 11V ≤ VCC ≤ 24V , 0V ≤ V

(With R
(Measured across R

= 200Ω, RS3 = 200Ω)R

S2

, Figure 1) (Note 2) R

S1

BOOST Pin Current V

= 4.93k 95 100 105 mV

PROG

= 4.93k ● 92 108 mV

PROG

= 49.3k 7 10 13 mV

R

PROG

= VSW + 8V, 0V ≤ VSW ≤ 20V

BOOST

TGATE High 2 3 mA
TGATE Low 2 3 mA

BOOSTC Pin Current V

= VCC + 8V 1 mA

BOOSTC

Reference

Reference Voltage (Note 3) R

= 4.93k, Measured at VFB with V

PROG

Supplying I

and Switching Off

PROG

Reference Voltage Tolerance 11V ≤ VCC ≤ 24V ● 2.441 2.489 V

BAT

≤ 20V

A

2.453 2.465 2.477 V

2

LT1505

ELECTRICAL CHARACTERISTICS

temperature range, otherwise specifications are at TA = 25°C. VCC = 18V, V

The ● denotes specifications which apply over the full operating

= 12.6V, V

BAT

= VCC (LT1505), no load on any

CLN

outputs unless otherwise noted.

PARAMETER CONDITIONS MIN TYP MAX UNITS
Preset Battery Voltage (12.3V, 16.4V, 12.6V, 16.8V)

All Preset Battery Voltages Measured at BAT2 Pin 0.5 %
Preset Battery Voltage Tolerance (V
BAT2 Pin Input Current V
Voltage Setting Resistors Tolerance (R4, R5, R6, R7) –40 40 %

Shutdown

Undervoltage Lockout (TGATE and BGATE “Off”) Measured at UV Pin ● 6.3 6.7 7.15 V
Threshold (Note 9)

UV Pin Input Current 0V ≤ VUV ≤ 8V ● –1 5 µA
Reverse Current from Battery in Micropower V

Shutdown (Note 10) V
Shutdown Threshold at SHDN Pin When V

is Connected
SHDN Pin Current 0V ≤ V
Supply Current in Shutdown VCC ≤ 24V 15 20 mA

(V

is Low, VCC is Connected)

SHDN

Minimum I
Minimum I

Current Sense Amplifier CA1 Inputs (SENSE, BAT)

Input Bias Current (SENSE, BAT) V

Input Common Mode Low ● –0.25 V
Input Common Mode High ● VCC – 0.3 V
SPIN Input Current V

Oscillator

Switching Frequency (f
Switching Frequency Tolerance ● 170 200 230 kHz
SYNC Pin Input Current V

Synchronization Pulse Threshold on SYNC Pin 0.9 1.2 2.0 V
Synchronization Frequency ● 240 280 kHz

Maximum Duty Cycle

V

BOOST

(Comparator A2) (Note 4) Low to High

Maximum Duty Cycle of Natural Frequency 200kHz ● 85 90 %
(Note 5)

Current Amplifier CA2

Transconductance VC = 1V, IVC = ±1µA 150 200 300 µmho
Maximum VC for Switch Off ● 0.6 V
IVC Current (Out of Pin) VC ≥ 0.6V ● 50 µA

VC at Shutdown V

for Switching “On” –1 –4 –22 µA

PROG

for Switching “Off” at V

PROG

) 180 200 220 kHz

NOM

Threshold to Turn TGATE Off Measured at (V

CC

≤ 1V ● –1 –2.4 mA

PROG

+ 0.3V) ≤ VCC ≤ 24V ● –1 1 %

BAT

= V

BAT2

≤ 20V, VUV ≤ 0.4V, 10 30 µA

BAT

= VSW = Battery Voltage

CC

SHDN

= High ● –50 – 120 µA

SHDN

V

= Low (Shutdown) –10 µA

SHDN

= High, V

SHDN

V

= Low (Shutdown) 10 µA

SHDN

= 0V –0.5 mA

SYNC

V

= 2V –30 µA

SYNC

Hysteresis 0.25 V

VC < 0.45V ● 3mA

= Low (Shutdown) ● 0.35 V

SHDN

– 1V ● 6 µA

PRESET

● 12V

≤ 3V 8 µA

≥ 2V (Note 8) ● 2mA

SPIN

– VSW)

BOOST

● 6.8 7.1 7.3 V

3

LT1505

ELECTRICAL CHARACTERISTICS

temperature range, otherwise specifications are at TA = 25°C. VCC = 18V, V

The ● denotes specifications which apply over the full operating

= 12.6V, V

BAT

= VCC (LT1505), no load on any

CLN

outputs unless otherwise noted.

PARAMETER CONDITIONS MIN TYP MAX UNITS
Voltage Amplifier VA

Transconductance (Note 3) Output Current from 50µA to 500µA 0.21 0.6 1.0 mho
Output Source Current VFB = V
VFB Input Bias Current At 0.5mA VA Output Current, TA = 25°C ±3 ±10 nA

At 0.5mA VA Output Current, T
(3 CELL, 4.1V, 4.2V Are Not Connected, V

Current Limit Amplifier CL1

Turn-On Threshold 0.5mA Output Current 87 92 97 mV
Transconductance Output Current from 50µA to 500µA 0.5 1 3 mho
CLP Input Current 0.5mA Output Current 1 3 µA
CLN Input Current 0.5mA Output Current 0.8 2 mA

Input P-Channel FET Driver (INFET)

INFET “On” Clamping Voltage (VCC – V
INFET “On” Driver Current V
INFET “Off” Clamping Voltage (VCC – V

)VCC ≥ 11V ● 6.5 7.8 9 V

INFET

INFET

)VCC Not Connected, I

INFET

INFET “Off” Drive Current VCC Not Connected, (VCC – V

Charging Completion Flag (Comparator E6)

Charging Completion Threshold (Note 6) Measured at V
Threshold On CAP Pin Low to High Threshold ● 3.3 4.2 V

High to Low Threshold ● 0.6 V

V

at Shutdown V

CAP

FLAG (Open Collector) Output Low V
FLAG Pin Leakage Current V

SHDN
CAP
CAP

Gate Drivers (TGATE, BGATE)

V

GBIAS

V

High (V

TGATE

V

High I

BGATE

V

Low (V

TGATE

V

Low I

BGATE

– VSW)I

TGATE

– VSW)I

TGATE

11V < VCC < 24V, I
V

SHDN
TGATE
BGATE
TGATE
BGATE

Peak Gate Drive Current 10nF Load 1 A
Gate Drive Rise and Fall Time 1nF Load 25 ns
V

, V

TGATE

at Shutdown V

BGATE

SHDN

I

TGATE

Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.

Note 2: Tested with Test Circuit 1.
Note 3: Tested with Test Circuit 2.
Note 4: When V

and battery voltage differential is low, high duty factor

CC

is required. The LT1505 achieves a duty factor greater than 99% by
skipping cycles. Only when V

drops below the comparator A2

BOOST

threshold will TGATE be turned off. See Applications Information.
Note 5: When the system starts, C2 (boost cap) has to be charged up to

drive TGATE and to start the system. The LT1505 will keep TGATE off and
turn BGATE on for 0.2µs at 200kHz to charge up C2. Comparator A2
senses V

and switches to the normal PWM mode when V

BOOST

above the threshold.

= V

PROG

+ 10mV 1.1 mA

REF

= 70°C –10 25 nA

A

BAT2

= 0V)

= VCC – 6V ● 820 mA

< –2µA 1.4 V

INFET

) ≥ 2V – 2.5 mA

INFET

, V

RS1

= 2V (Note 7) 14 20 28 mV

CAP

= Low (Shutdown) ● 0.13 0.3 V

= 4V, I

< 1mA ● 0.3 V

FLAG

= 0.6V ● 3 µA

≤ 15mA ● 8.4 8.9 9.3 V

GBIAS

= Low (Shutdown) ● 13 V
≤ 20mA, V

BOOST

= V

– 0.5V ● 5.6 6.6 V

GBIAS

≤ 20mA ● 6.2 7.2 V
≤ 50mA ● 0.8 V
≤ 50mA ● 0.8 V

= Low (Shutdown) ● 1V
= I

= 10µA

BGATE

Note 6: See “Lithium-Ion Charging Completion” in the Applications
Information Section.

Note 7: Tested with Test Circuit 3.
Note 8: I

not present to avoid high surge current from C

keeps switching on to keep V

SPIN

regulated when battery is

BAT

when battery is

OUT

inserted.
Note 9: Above undervoltage threshold switching is enabled.

BOOST

is

Note 10: Do not connect V
will cause the internal diode between V
and may cause high current to flow from V
removed, V

will be held up by the body diode of M1.

CC

directly to V

CC

(see Figure 1). This connection

IN

and VCC to be forward-biased

BAT

. When the adapter is

IN

4

UW

TYPICAL PERFORMANCE CHARACTERISTICS

LT1505

Efficiency of Figure 1 Circuit

105

VIN = 19V

= 12.6V

V

BAT

100

95

90

EFFICIENCY (%)

85

(mV)

FB

∆V

80

4

3

2

1

1

0

∆V

vs IVA (Voltage Amplifier)

FB

2

I

BAT

(A)

3

125°C

25°C

V

vs I

GBIAS

9.2

9.1

9.0

8.9

8.8

(V)

8.7

GBIAS

V

8.6

8.5

8.4

8.3

4

5

1505 G01

8.1
0 –2–4–6

GBIAS

125°C

–8

I

0°C

25°C

–12 –14 –16 –18 –20

–10

(mA)

GBIAS

1505 G02

0.003

0.002

0.001

(V)

REF

∆V

–0.001

–0.002

–0.003

V

Line Regulation

REF

0°C ≤ TJ ≤ 125°C

0

0

5

ALL TEMPERATURES

10 15 20

VCC (V)

25 30

1505 G03

Current Limit Amplifier
CL1 Threshold

98

96

94

92

THRESHOLD (mV)

90

(mA)

CC

I

ICC vs V

15

14

13

12

11

CC

0°C

25°C

125°C

0

0.20.1 0.3 0.5 0.7 0.9

0

0.4
IVA (mA)

PROG Pin Characteristics

6

CURRENT FEEDBACK
AMPLIFIER OPEN LOOP

(mA)

0

PROG

I

–6

0123

V

PROG

(V)

0.6

125°C

0.8

1505 G04

25°C

1505 G07

1.0

88

0 255075100

TEMPERATURE (°C)

125

1505 G05

VC Pin Characteristics

–1.2
–1.0
–0.8
–0.6
–0.4
–0.2

(mA)

0

VC

I

0.2

0.4

0.6

0.8

54

1.0
0 0.4 0.60.2

0.8 1.0

1.2 1.4 1.6 1.8 2.0

VC (V)

1505 G08

10

10 13

16

V

(V)

CC

19 22 25

Reference Voltage vs Temperature

2.470

2.468

2.466

2.464

2.462

REFERENCE VOLTAGE (V)

2.460

2.458
0

50 75 100

25

JUNCTION TEMPERATURE (°C)

1505 G06

125 150

1505 G09

5

LT1505

UUU

PIN FUNCTIONS

BOOST (Pin 1): This pin is used to bootstrap and supply
power for the topside power switch gate drive and control
circuity. In normal operation, V
internally generated 8.6V regulator V
+ 8.9V when TGATE is high. Do not force an external
voltage on BOOST pin.

TGATE (Pin 2): This pin provides gate drive to the topside
power FET. When TGATE is driven on, the gate voltage will
be approximately equal to VSW + 6.6V. A series resistor of
5Ω to 10Ω should be used from this pin to the gate of the
topside FET.

SW (Pin 3): This pin is the reference point for the floating
topside gate drive circuitry. It is the common connection
for the top and bottom side switches and the output
inductor. This pin switches between ground and VCC with
very high dv/dt rates. Care needs to be taken in the PC
layout to keep this node from coupling to other sensitive
nodes. A 1A Schottky clamp diode should be placed from
this pin to the ground pin, using very short traces to
prevent the chip substrate diode from turning on. See
Applications Information for more details.

SYNC (Pin 4): Synchronization Input. The LT1505 can be
synchronized to an external clock with pulses that have
duty cycles between 10% and 95%. An internal one shot
that is triggered on the rising edge of the sync pulse makes
this input insensitive to the duty cycle of the sync pulse.
The input voltage range on this pin is 0V to 20V. This pin
can float if not used.

SHDN (Pin 5): Shutdown. When this pin is pulled below 1V,
switching will stop, GBIAS will go low and the input cur­rents of CA1 will be off. Note that input current of about 4µA
keeps the device in shutdown unless an external pull-up
signal is applied. The voltage range on this pin is 0V to VCC.

AGND (Pin 6): Low Current Analog Ground.
UV (Pin 7): Undervoltage Lockout Input. The rising thresh-

old is 6.7V with a hysteresis of 0.5V. Switching stops in
undervoltage lockout. When the input supply (normally
the wall adapter output) to the chip is removed, the UV pin
must be pulled down to below 0.7V (a 5k resistor from
adapter output to GND is required), otherwise the reverse­battery current will be approximately 200µA instead of
10µA. Do not leave the UV pin floating. If it is connected

is powered from an

BOOST

, V

GBIAS

BOOST

≈ V

CC

to VIN with no resistor divider, the built-in 6.7V undervoltage
lockout will be effective. Maximum voltage allowed on this
pin is VCC.

INFET (Pin 8): For very low dropout applications, an
external P-channel MOSFET can be used to connect the
input supply to VCC. This pin provides the gate drive for the
PFET. The gate drive is clamped to 8V below VCC. The gate
is driven on (low) when VCC >(V
VUV > 6.7V. The gate is off (high) when VCC < (V
The body diode of the PFET is used to pull up VCC to turn
on the LT1505.

CLP (Pin 9): LT1505: Positive Input to the Input Current
Limit Amplifier CL1. The threshold is set at 92mV. When
used to limit input current, a filter is needed to filter out the
200kHz switching noise. (LT1505-1: No Connection.)

CLN (Pin 10): LT1505: Negative Input to the Input Current
Limit Amplifier CL1. When used, both CLP and CLN should
be connected to a voltage higher than 6V and normally
VCC (to the VCC bypass capacitor for less noise). Maximum
voltage allowed on both CLP and CLN is VCC + 1V.
(LT1505-1: No Connection.)

COMP1 (Pin 11): LT1505: Compensation Node for the
Input Current Limit Amplifier CL1. At input adapter current
limit, this pin rises to 1V. By forcing COMP1 low with an
external transistor, amplifier CL1 will be disabled (no
adapter current limit). Output current is less than 0.2mA.
See the Figure 1 circuit for the required resistor and
capacitor values. (LT1505-1: connect to GND.)

CAP (Pin 12): A 0.1µF capacitor from CAP to ground is
needed to filter the sampled charging current signal. This
filtered signal is used to set the FLAG pin when the
charging current drops below 20% of the programmed
maximum charging current.

FLAG (Pin 13): This pin is an open-collector output that is
used to indicate the end of charge. The FLAG pin is driven
low when the charge current drops below 20% of the
programmed charge current. A pull-up resistor is
required if this function is used. This pin is capable of
sinking at least 1mA. Maximum voltage on this pin is VCC.

4.1V (Pin 14), 4.2V (Pin 15), 3CELL (Pin 16), VFB (Pin

17): These four pins are used to select the battery voltage

using the preset internal resistor network. The VFB pin is

+ 0.2V) and

BAT

+ 0.2V).

BAT

6

UUU

PIN FUNCTIONS

LT1505

the noninverting input to the amplifier, VA in the Block
Diagram, that controls the charging current when the
device operates in constant voltage mode. The amplifier
VA controls the charging current to maintain the voltage
on the VFB pin at the reference voltage (2.465V). Input bias
current for VA is approximately 3nA. The LT1505 incorpo­rates a resistor divider that can be used to select the
correct voltage for either three or four 4.1V or 4.2V
lithium-ion cells. For three cells the 3CELL pin is shorted
to the VFB pin. For four cells the 3CELL pin is not con­nected. For 4.1V cells the 4.1V pin is connected to the V
pin and the 4.2V pin is not connected. For 4.2V cells the

4.2V pin is connected to VFB and the 4.1V pin is not
connected. See the table below.

PRESET BATTERY VOLTAGE PIN SELECTION

12.3V (3 × 4.1V Cell) 4.1V, VFB, 3CELL Short Together

16.4V (4 × 4.1V Cell) 4.1V, VFB, Short Together, 3CELL Floats

12.6V (3 × 4.2V Cell) 4.2V, VFB, 3CELL Short Together

16.8V (4 × 4.2V Cell) 4.2V, VFB, Short Together, 3CELL Floats

For battery voltages other than the preset values, an
external resistor divider can be used. If an external divider
is used then the 4.1V, 4.2V and 3CELL pins should not be
connected and BAT2 pin should be grounded. To maintain
the tight voltage tolerance, the external resistors should
have better than 0.25% tolerance. Note that the VFB pin will
float high and inhibit switching if it is left open.

VC (Pin 18): This is the control signal of the inner loop of
the current mode PWM. Switching starts at 0.9V, higher
VC corresponds to higher charging current in normal
operation and reaches 1.1V at full charging current. A
capacitor of at least 0.33µF to GND filters out noise and
controls the rate of soft start. Pulling this pin low will stop
switching. Typical output current is 60µA.

PROG (Pin 19): This pin is for programming the charge
current and for system loop compensation. During normal
operation, V
more than 1mA is drawn out of the pin, switching will stop.
When a microprocessor controlled DAC is used to pro­gram charging current, it must be capable of sinking
current at a compliance up to 2.465V.

stays at 2.465V. If it is shorted to GND or

PROG

FB

BAT2 (Pin 20): This pin is used to connect the battery to
the internal preset voltage setting resistor. An internal
switch disconnects the internal divider from the battery
when the device is in shutdown or when power is discon­nected. This disconnect function eliminates the current
drain due to the resistor divider. This pin should be
connected to the positive node of the battery if the internal
preset divider is used. This pin should be grounded if an
external divider is used. Maximum input voltage on this
pin is 20V.

SENSE (Pin 21): This pin is the noninverting input to the
current amplifier CA1 in the Block Diagram. Typical bias
current is –50µA.

SPIN (Pin 22): This pin is for the internal amplifier CA1
bias. It must be connected as shown in the application
circuit.

BAT (Pin 23): Current Amplifier CA1 Inverting Input.
Typical bias current is –50µA.

VCC (Pin 24): Input Supply. For good bypass, a low ESR
capacitor of 10µF or higher is required. Keep the lead
length to a minimum. VCC should be between 11V and 24V.
Do not force VCC below V
battery present.

BOOSTC (Pin 25): This pin is used to bootstrap and supply
the current sense amplifier CA1 for very low dropout
condition. VCC can be as low as only 0.4V above the battery
voltage. A diode and a capacitor are needed to get the
voltage from V
is always 3V or higher than V
floating or tied to VCC. Do not force this pin to a voltage
lower than VCC. Typical input current is 1mA.

GBIAS (Pin 26): This is the output of the internal 8.6V
regulator to power the drivers and control circuits. This pin
must be bypassed to a ground plane with a minimum of

2.2µF ceramic capacitor. Switching will stop when V
drops below 7V.

BGATE (Pin 27): Low Side Power MOSFET Drive.
PGND (Pin 28): MOSFET Driver Power Ground. A solid

system ground plane is very important. See the LT1505
Demo Manual for further information.

. If low dropout is not needed and V

BOOST

by more than 1V with the

BAT

, this pin can be left

BAT

CC

GBIAS

7

LT1505

BLOCK DIAGRAM

W

(LT1505)

V

IN

8

V

CC

6.7V

–

+

–

+

SHOT

ONE

0.2V

–

E2

+

+

+

+

E1

–

SHUTDOWN

E5

E7

E4

SR

OSC
200k

I

VA

4

PWM

I

–

+

+

PROG

–

3.3V

UV

7

BAT

V

24

CC

GBIAS

V

IN

SHDN

SYNC

CAP

FLAG

+

7V

5

4U

+

1.3V

4

12

13

E6

6.7V

+

E3

C1

+

–

4V

VR

S1

+

0.02V

SLOPE COMP

+

E8

SHUTDOWN

SW

+

+

–

V

CC

7.8V

A13

Q4

+

–

+

7V

2.5V

–

+

+

A8

A10

Q2

Q1

I

PROG

R1
1k

I

VA

–

A4

+

A6

A12

BGATE

A5

A7

Q3

–

B1

R2

R3

+

–

CA2

C

+

PROG

V

REF

PROG

R

PROG

R8
75k

6

AGND

V

C

INFET

A2

A3

111918

VA

CL1*

V

CC

A1

+

8.9V

A9

+

CA1

–

R4

50.55k

R5
21k

+

–

V

REF

2.465V

92mV

+

+

–

COMP1

*LT1505 ONLY. SEE PIN FUNCTIONS
FOR LT1505-1 CONNECTIONS

A11

I

PROG

R6

0.33k

R7

12.3k

V

BOOST

1

TGATE

2

50k

SW

3

GBIAS

26

4.7µF

BGATE

27

50k

PGND

28

BOOSTC

25

SPIN

22

SENSE

21

BAT

23

BAT2

+

20

CC

C2
1µF

M1

VR

L1

10µH

C3

I

BAT

M2

R

S3

R

S2

S1

+–

R

S1

+

12.6V
BATTERY

–

3CELL

16

V

FB

17

4.1V

14

4.2V

15

V

IN

CLP

1505 BD

9

CLN

10

SYSTEM

LOAD

R

S

V

CC

8

TEST CIRCUITS

LT1505

Test Circuit 1

SPIN

R

S3

200Ω

SENSE

+

R

S2

200Ω

BAT

–

R
10Ω

S1

+

V

BAT

0.047µF

LT1505

–

V

C

75k

CA2

+

V

300Ω

REF

1µF

1k

PROG

R

PROG

CA1

+

1k

+

≈ 0.65V

LT1006

–

1505 TC01

20k

Test Circuit 2

LT1505

VFB OR BAT2

2nF

I

PROG

PROG

+

VA

V

–

REF

2k

–

0.033µF

0.047µF

+

2V

1k

–+

LT1013

20k

CAP

FLAG

0.47µF

R

PROG

LT1013

+

+

2.465V

1505 TC02

Test Circuit 3

R

LT1505

I

VA

–

E6

+

4

I

PROG

I

PROG

CA1

+

3.3V

I

VA

PROG

10k

0.47µF

4.93k

SENSE

+

BAT

–

V

+

VA

V

–

REF

10k

–

LT1013

+

+

2.465V

S3

200Ω

+

R

V

S2

200Ω

RS1

10Ω

–

+

V

FB

BAT

1505 TC03

9

LT1505

U

OPERATION

The LT1505 is a synchronous current mode PWM step­down (buck) switcher. The battery DC charge current is pro­grammed by a resistor R
the PROG pin and the ratio of sense resistors RS2 over R
(see Block Diagram). Amplifier CA1 converts the charge cur­rent through RS1 to a much lower current I
I

• RS1/RS2) fed into the PROG pin. Amplifier CA2 com-

BAT

pares the output of CA1 with the programmed current and
drives the PWM loop to force them to be equal. High DC
accuracy is achieved with averaging capacitor C
that I
through R1 and generates a ramp signal that is fed to the
PWM control comparator C1 through buffer B1 and level
shift resistors R2 and R3, forming the current mode inner
loop. The BOOST pin supplies the topside power switch gate
drive. The LT1505 generates an 8.6V V
and V
CA1 with a voltage higher than VCC for low dropout appli­cation. For batteries like lithium that require both constant­current and constant-voltage charging, the 0.5% 2.465V
reference and the amplifier VA reduce the charge current
when battery voltage reaches the preset level. For NiMH and
NiCd, VA can be used for overvoltage protection.

The amplifier CL1 monitors and limits the input current,
normally from the AC adapter, to a preset level (92mV/RS).

has both AC and DC components. I

PROG

BOOSTC

. BOOSTC pin supplies the current amplifier

(or a DAC output current) at

PROG

PROG (IPROG

PROG

to power drives

GBIAS

PROG

S1

=

. Note
goes

At input current limit, CL1 will supply the programming
current I

To prevent current shoot-through between topside and
lowside switches, comparators A3 and A4 assure that one
switch turns off before the other is allowed to turn on.
Comparator A12 monitors charge current level and turns
lowside switch off if it drops below 20% of the programmed
value (20mV across RS1) to allow for inductor discontinu­ous mode operation. Therefore sometimes even in con­tinuous mode operation with light current level the lowside
switch stays off.

Comparator E6 monitors the charge current and signals
through the FLAG pin when the charger is in voltage mode
and the charge current level is reduced to 20%. This charge
complete signal can be used to start a timer for charge
termination.

The INFET pin drives an external P-channel FET for low
dropout application.

When input voltage is removed, VCC will be held up by the
body diode of the topside MOSFET. The LT1505 goes into
a low current, 10µA typical, sleep mode as VCC drops
below the battery voltage. To shut down the charger
simply pull the VC pin or SHDN pin low with a transistor.

, thus reducing battery charging current.

PROG

U

WUU

APPLICATIONS INFORMATION

Input and Output Capacitors

In the 4A Lithium Battery Charger (Figure 1), the input
capacitor (CIN) is assumed to absorb all input switching
ripple current in the converter, so it must have adequate
ripple current rating. Worst-case RMS ripple current will
be equal to one half of output charging current. Actual
capacitance value is not critical. Solid tantalum capacitors
such as the AVX TPS and Sprague 593D series have high
ripple current rating in a relatively small surface mount
package, but

tors are used for input bypass

can be created when the adapter is hot-plugged to the
charger and solid tantalum capacitors have a known
failure mechanism when subjected to very high turn-on
surge currents. Highest possible voltage rating on the

caution must be used when tantalum capaci-

. High input surge currents

10

capacitor will minimize problems. Consult the manufac­turer before use. Alternatives include new high capacity
ceramic (at least 20µF) from Tokin or United Chemi-Con/
Marcon, et al.

The output capacitor (C
output switching current ripple. The general formula for
capacitor current is:

0.29 (V

I

=

RMS

For example, VCC = 19V, V
and f = 200kHz, I

BAT

(L1)(f)

RMS

) is also assumed to absorb

OUT

V

) 1 –

= 0.4A.

BAT

()

V

CC

= 12.6V, L1 = 15µH,

BAT

LT1505

U

WUU

APPLICATIONS INFORMATION

EMI considerations usually make it desirable to minimize
ripple current in the battery leads. Beads or inductors may
be added to increase battery impedance at the 200kHz
switching frequency. Switching ripple current splits be­tween the battery and the output capacitor depending on
the ESR of the output capacitor and the battery imped­ance. If the ESR of C
is raised to 4Ω with a bead or inductor, only 5% of the
ripple current will flow in the battery.

Soft Start and Undervoltage Lockout

The LT1505 is soft started by the 0.33µF capacitor on the
VC pin. On start-up, the VC pin voltage will rise quickly to

0.5V, then ramp up at a rate set by the internal 45µA pull-
up current and the external capacitor. Battery charge
current starts ramping up when VC voltage reaches 0.7V
and full current is achieved with VC at 1.1V. With a 0.33µF
capacitor, time to reach full charge current is about 10ms
and it is assumed that input voltage to the charger will
reach full value in less than 10ms. The capacitor can be
increased up to 1µF if longer input start-up times are
needed.

In any switching regulator, conventional timer-based soft
starting can be defeated if the input voltage rises much
slower than the time out period. This happens because the
switching regulators in the battery charger and the com­puter power supply are typically supplying a fixed amount
of power to the load. If input voltage comes up slowly
compared to the soft start time, the regulators will try to
deliver full power to the load when the input voltage is still
well below its final value. If the adapter is current limited,
it cannot deliver full power at reduced output voltages and
the possibility exists for a quasi “latch” state where the
adapter output stays in a current limited state at reduced
output voltage. For instance, if maximum charger plus
computer load power is 30W, a 15V adapter might be
current limited at 2.5A. If adapter voltage is less than
(30W/2.5A = 12V) when full power is drawn, the adapter
voltage will be pulled down by the constant 30W load until
it reaches a lower stable state where the switching regu­lators can no longer supply full load. This situation can be
prevented by setting
minimum adapter voltage where full power can be achieved.

is 0.2Ω and the battery impedance

OUT

undervoltage lockout

higher than the

92mV

+

CL1

–

LT1505

Figure 2. Adapter Current Limiting

CLP

+

1µF

CLN

V

CC

+

UV

*R

=

S4

ADAPTER CURRENT LIMIT

500Ω

AC ADAPTER

RS4*

C

IN

92mV

OUTPUT

R5

R6

1505 F02

V

IN

A resistor divider is used to set the desired VCC lockout
voltage as shown in Figure 2. A typical value for R6 is 5k
and R5 is found from:

R6(V – V )

R5 =

UV

IN

V

UV

VUV = Rising lockout threshold on the UV pin
VIN = Charger input voltage that will sustain full load power
Example: With R6 = 5k, VUV = 6.7V and setting VIN at 16V;
R5 = 5k (16V – 6.7V)/6.7V = 6.9k
The resistor divider should be connected directly to the

adapter output as shown, not to the VCC pin to prevent
battery drain with no adapter voltage. If the UV pin is not
used, connect it to the adapter output (not VCC) and
connect a resistor no greater than 5k to ground. Floating
the pin will cause reverse battery current to increase from
10µA to 200µA.

Adapter Current Limiting
(Not Applicable for the LT1505-1)

An important feature of the LT1505 is the ability to
automatically adjust charge current to a level which avoids
overloading the wall adapter. This allows the product to
operate at the same time batteries are being charged
without complex load management algorithms. Addition­ally, batteries will automatically be charged at the maximum
possible rate of which the adapter is capable.

11

LT1505

U

WUU

APPLICATIONS INFORMATION

This is accomplished by sensing total adapter output
current and adjusting charge current downward if a preset
adapter current limit is exceeded. True analog control is
used, with closed loop feedback ensuring that adapter load
current remains within limits. Amplifier CL1 in Figure 2
senses the voltage across RS4, connected between the
CLP and CLN pins. When this voltage exceeds 92mV, the
amplifier will override programmed charge current to limit
adapter current to 92mV/RS4. A lowpass filter formed by
500Ω and 1µF is required to eliminate switching noise. If
the current limit is not used, then the R7 /C1 filter and the
COMP1 (R1/C7) compensation networks are not needed,
and both CLP and CLN pins should be connected to VCC.

Charge Current Programming

The basic formula for charge current is (see Block
Diagram):

I

BAT

where R

R

= I

PROG

is the total resistance from PROG pin to ground.

PROG

S2

()

R

S1

2.465V

=

()()

R

PROG

R

S2

R

S1

RS2 = RS3 =

(I

BAT

)(R

PROG

)(RS1)

2.465V

(4A)(5k)(0.025)

= = 200Ω

2.465V

Charge current can also be programmed by pulse width
modulating I

with a switch Q1 to R

PROG

at a frequency

PROG

higher than a few kHz (Figure 3). Charge current will be
proportional to the duty cycle of the switch with full current
at 100% duty cycle.

When a microprocessor DAC output is used to control
charge current, it must be capable of sinking current at a
compliance up to 2.5V if connected directly to the PROG
pin.

Lithium-Ion Charging

The 4A Lithium Battery Charger (Figure 1) charges lithium­ion batteries at a constant 4A until battery voltage reaches
the preset value. The charger will then automatically go
into a constant-voltage mode with current decreasing to
near zero over time as the battery reaches full charge.

For the sense amplifier CA1 biasing purpose, RS3 should
have the same value as RS2 and SPIN should be connected
directly to the sense resistor (RS1) as shown in the Block
Diagram.

For example, 4A charging current is needed. For low power
dissipation on R

and enough signal to drive the amplifier

S1

CA1, let RS1 = 100mV/4A = 0.025Ω. This limits RS1 power
to 0.4W. Let R

Figure 3. PWM Current Programming

PROG

5V
0V

I

= (DC)(4A)

BAT

PWM

= 5k, then:

LT1505

R

4.7k

Q1
VN2222

PROG

PROG

C

PROG

1µF

1505 F03

Preset Battery Voltage Settings

The LT1505 provides four preset battery voltages: 12.3V,

12.6V, 16.4V and 16.8V. See the Pin Functions section for
pin setting voltage selection. An internal switch connects
the resistor dividers to the battery sense pin, BAT2. When
shutting down the LT1505 by removing adaptor power or
by pulling the SHDN pin low, the resistor dividers will be
disconnected and will not drain the battery. The BAT2 pin
should be connected to the battery when any of the preset
battery voltages are used.

External Battery Voltage Setting Resistors

When an external divider is used for other battery voltages,
BAT2 should be grounded. Pins 4.1V, 4.2V and 3CELL
should be left floating. To minimize battery drain when the
charger is off, current through the R3/R4 divider (Figure 4)
is set at 15µA . The input current to the VFB pin is 3nA and
the error can be neglected.

12

LT1505

U

WUU

APPLICATIONS INFORMATION

With divider current set at 15µA, R4 = 2.465/15µA = 162k
and,

R3

R4 V 2.465

()

=

−

()

BAT

2.465

=

390k

Li-Ion batteries typically require float voltage accuracy of
1% to 2%. Accuracy of the LT1505 VFB voltage is ±0.5%
at 25°C and ±1% over the full temperature range. This
leads to the possibility that very accurate (0.1%) resistors
might be needed for R3 and R4. Actually, the temperature
of the LT1505 will rarely exceed 50°C in float mode
because charging currents have tapered off to a low level,
so 0.25% resistors will normally provide the required level
of overall accuracy.

LT1505

V

FB

Figure 4. External Resistor Divider

Lithium-Ion Charging Completion

Some battery manufacturers recommend termination of
constant-voltage float mode after charge current has
dropped below a specified level (typically around 20% of
the full current) and a further time-out period of 30
minutes to 90 minutes has elapsed. Check with manufac­turers for details. The LT1505 provides a signal at the
FLAG pin when charging is in voltage mode and current is
reduced to 20% of full current, assuming full charge
current is programmed to have 100mV across the current
sense resistor (V

). The comparator E6 in the Block

RS1

Diagram compares the charge current sample I
output current IVA voltage amplifier VA. When the charge
current drops to 20% of full current, I

0.25 IVA and the open-collector output V
and can be used to start an external timer. When this
feature is used, a capacitor of at least 0.1µF is required at
the CAP pin to filter out the switching noise and a pull-up

162k 8.4 2.465

=

−

()

2.465

R3
390k

0.25%
R4

162k

0.25%

+

V

8.4V

1505 F04

will be equal to

PROG

FLAG

BAT

to the

PROG

will go low

resistor is also needed at the FLAG pin. If this feature is not
used, C6 is not needed.

Very Low Dropout Operation

The LT1505 can charge the battery even when VCC goes
as low as 0.5V above the combined voltages of the
battery and the drops on the sense resistor as well as
parasitic wiring. This low VCC sometimes requires a duty
factor greater then 99% and TGATE stays on for many
switching cycles. While TGATE stays on, the voltage
V

across the capacitor C2 drops down because

BOOST

TGATE control circuits require 2mA DC current. C2 needs
to be recharged before V

drops too low to keep the

BOOST

topside switch on. A unique design allows the LT1505 to
operate under these conditions; the comparator A2 moni­tors V

and when it drops from 8.9V to 6.9V, TGATE

BOOST

will be turned off for about 0.2µs to recharge C2. Note that
the LT1505 gets started the same way when power turns
on and there is no initial V

BOOST

.

It is important to use 0.56µF or greater value for C2 to hold
V

up for a sufficient amount of time.

BOOST

When minimum operating VCC is less than 2.5V above the
battery voltage, D3 and C4 (see Figure 1) are also needed
to bootstrap V

BOOSTC

higher than VCC to bias the current
amplifier CA1. They are not needed if VCC is at least 2.5V
higher than V
replaced with a diode if VIN is at least 3V higher than V

. The PFET M3 is optional and can be

BAT

BAT

.
The gate control pin INFET turns on M3 when VIN gets up
above the undervoltage lockout level set by R5 and R6 and
is clamped internally to 8V below VCC. In sleep mode when
VIN is removed, INFET will clamp M3 VSG to 0.2V.

Shutdown

When adapter power is removed, VCC will drift down and
be held by the body diode of the topside NFET switch. As
soon as VCC goes down to 0.2V above V

, the LT1505 will

BAT

go into sleep mode drawing only 10µA from the battery.
There are two ways to stop switching: pulling the SHDN

pin low or pulling the VC pin low. Pulling the SHDN pin low
will also turn off V
VC pin low will only stop switching and V

and CA1 input currents. Pulling the

GBIAS

stays high.

GBIAS

Make sure there is a pull-up resistor on the SHDN pin even

13

LT1505

R2

5.49k

R1

49.3k

PROG

C

PROG

1µF

Q1

LT1505

1505 F07

U

WUU

APPLICATIONS INFORMATION

if the SHDN pin is not used, otherwise internal pull-down
current will keep the SHDN pin low and switching off when
power turns on.

Each TGATE and BGATE pin has a 50k pull-down resistor
to keep the external power FETs off when shut down or
power is off.

Note that maximum operating VCC is 24V. For short
transients the LT1505 can be operated as high as 27V. For
VCC higher than 24V it is preferred to use the VC pin to shut
down. If the SHDN pin has to be used to shut down at V
higher than 24V, the Figure 5 pull-up circuit must be used
to slow down the V

ramp-up rate when the SHDN pin

GBIAS

is released. Otherwise, high surge current charging the
bypass capacitor might damage the LT1505. For VCC less
than 24V, only a 100k resistor and no capacitor is needed
at SHDN pin to VIN for pull-up.

Synchronization

CC

24V ≤ VCC < 27V

LT1505

PULSE WIDTH > 200ns

V

IN

SHDN

Figure 5

5V TO 20V

5k

VN2222

Figure 6

3M

OPEN DRAIN

3.3µF

1505 F05

LT1505

SYNC

1505 F06

The LT1505 can be synchronized to a frequency range
from 240kHz to 280kHz. With a 200ns one-shot timer on
chip, the LT1505 provides flexibility on the synchronizing
pulse width. Sync pulse threshold is about 1.2V (Figure 6).

Nickel-Cadmium and Nickel-Metal-Hydride Charging

The circuit in the 4A Lithium Battery Charger (Figure 1) can
be modified to charge NiCd or NiMH batteries. For
example, 2-level charging is needed; 2A when Q1 is on,
and 200mA when Q1 is off (Figure 7).

For 2A full current, the current sense resistor (RS1) should
be increased to 0.05Ω so that enough signal (10mV) will
be across RS1 at 0.2A trickle charge to keep charging
current accurate.

For a 2-level charger, R1 and R2 are found from:

2.465 4000

()()

R1

=

I

LOW HI LOW

R2

2.465 4000

()()

=

−

II

All battery chargers with fast charge rates require some
means to detect full charge state in the battery to terminate
the high charge current. NiCd batteries are typically charged
at high current until temperature rise or battery voltage
decrease is detected as an indication of near full charge.

Figure 7. 2-Level Charging

The charge current is then reduced to a much lower value
and maintained as a constant trickle charge. An interme­diate “top off” current may be used for a fixed time period
to reduce 100% charge time.

NiMH batteries are similar in chemistry to NiCd but have
two differences related to charging. First, the inflection
characteristic in battery voltage as full charge is ap­proached is not nearly as pronounced. This makes it
more difficult to use –∆V as an indicator of full charge,
and an increase in temperature is more often used with
a temperature sensor in the battery pack. Secondly,
constant trickle charge may not be recommended.

14

LT1505

1505 F09

SHDN

LT1505

D5
1N4148

100k

V

BAT

V

IN

U

WUU

APPLICATIONS INFORMATION

Instead, a moderate level of current is used on a pulse
basis (≈1% to 5% duty cycle) with the time-averaged
value substituting for a constant low trickle. Please
contact the Linear Technology Applications department
about charge termination circuits.

If overvoltage protection is needed, R3 and R4 in Figure 4
should be calculated according to the procedure described
in the Lithium-Ion Charging section. The VFB pin should be
grounded if not used.

Charger Crowbar Protection

If the VIN connector of Figure 1 can be instantaneously
shorted (crowbarred) to ground, then a small P-channel FET
M4 should be used to quickly turn off the input
P-channel FET M3 (see Figure 8), otherwise, high reverse
surge current might damage M3. M3 can also be replaced
by a diode if dropout voltage and heat dissipation are not
problems.

R

V

IN

M3

Figure 8. VIN Crowbar Protection

Figure 9. V

BAT

S4

M4
TPO610

INFET

Crowbar Protection

LT1505

1505 F08

V

CC

Note that the LT1505 will operate even when V
grounded. If V

of Figure 1 charger gets shorted to

BAT

BAT

is

ground very quickly (crowbarred) from a high battery
voltage, slow loop response may allow charge current to
build up and damage the topside N-channel FET M1. A
small diode D5 (see Figure 9) from the SHDN pin to V

BAT

will shut down switching and protect the charger.
Note that M4 and/or D5 are needed only if the charger

system can be potentially crowbarred.

Layout Considerations

Switch rise and fall times are under 20ns for maximum
efficiency. To prevent radiation, the power MOSFETs, the
SW pin and input bypass capacitor leads should be kept as
short as possible. A Schottky diode (D4 in Figure 1) rated

for at least 1A is necessary to clamp the SW pin and should
be placed close to the low side MOSFET. A ground plane
should be used under the switching circuitry to prevent
interplane coupling and to act as a thermal spreading path.
Note that the inductor is probably the most heat dissipat­ing device in the charging system. The resistance on a 4A,
15µH inductor, can be 0.03Ω . With DC and AC losses, the
power dissipation can go as high as 0.8W. Expanded
traces should be used for the inductor leads for low
thermal resistance.

The fast switching high current ground path including the
MOSFETs, D4 and input bypass capacitor should be kept
very short. Another smaller input bypass (1µF ceramic)
should be placed very close the chip. The demo board
DC219 should be used for layout reference.

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.

15

LT1505

PACKAGE DESCRIPTION

0.205 – 0.212**
(5.20 – 5.38)

U

Dimensions in inches (millimeters) unless otherwise noted.

G Package

28-Lead Plastic SSOP (0.209)

(LTC DWG # 05-08-1640)

0.397 – 0.407*

(10.07 – 10.33)

2526 22 21 20 19 181716 1523242728

0.301 – 0.311
(7.65 – 7.90)

12345678 9 10 11 12 1413

0.068 – 0.078
(1.73 – 1.99)

° – 8°

0

0.005 – 0.009
(0.13 – 0.22)

*

DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE

**

DIMENSIONS DO NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE

0.022 – 0.037
(0.55 – 0.95)

0.0256
(0.65)

BSC

0.010 – 0.015
(0.25 – 0.38)

0.002 – 0.008
(0.05 – 0.21)

G28 SSOP 0694

RELATED PARTS

PART NUMBER DESCRIPTION COMMENTS

LTC®1325 Microprocessor-Controlled Battery Management System Can Charge, Discharge and Gas Gauge NiCd and Lead-Acid

Batteries with Software Charging Profiles
LT1372/LT1377 1.5A, 500kHz/1MHz Step-Up Switching Regulators High Frequency, Small Inductor, High Efficiency Switchers, SO-8
LT1376 1.5A, 500kHz Step-Down Switching Regulator High Frequency, Small Inductor, High Efficiency Switcher, SO-8
LT1510 Constant-Voltage/Constant-Current Battery Charger Up to 1.5A Charge Current, Small SO-8 Footprint
LT1511 3A Constant-Voltage/Constant-Current Battery Charger Charges Lithium, NiCd and NiMH Batteries, 28-Lead SO Package
LT1512 SEPIC CC/CV Battery Charger VIN Can Be Higher or Lower Than Battery Voltage, 2A Internal Switch
LT1513 SEPIC CC/CV Battery Charger VIN Can Be Higher or Lower Than Battery Voltage, 3A Internal Switch
LTC1759 SMBus Controlled Smart Battery Charger LT1505 Charger Functionality with SMBus Control
LT1769 2A Constant-Voltage/Constant-Current Battery Charger Charges Lithium, NiCd and NiMH Batteries, 28-Lead SSOP

16

Linear T echnology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

[phone] ● FAX: [phone]

●

www.linear-tech.com

1505fa LT/TP 0400 2K REV A • PRINTED IN USA

 LINEAR TECHNOLOGY CORPORATION 1999