LINEAR TECHNOLOGY LTC4081 Technical data

LTC4081

500mA Li-Ion Charger

with NTC Input and

FEATURES

Battery Charger:

■

Constant-Current/Constant-Voltage Operation

with Thermal Feedback to Maximize Charge Rate
Without Risk of Overheating

■

Internal 4.5 Hour Safety Timer for Termination

■

Charge Current Programmable Up to 500mA with

5% Accuracy

■

NTC Thermistor Input for Temperature Qualifi ed

Charging

■

C/10 Charge Current Detection Output

■

5μA Supply Current in Shutdown Mode

Switching Regulator:

■

High Effi ciency Synchronous Buck Converter

■

300mA Output Current (Constant-Frequency Mode)

■

2.7V to 4.5V Input Range (Powered from BAT Pin)

■

0.8V to V

■

MODE Pin Selects Fixed (2.25MHz) Constant-Frequency

PWM Mode or Low I

■

2μA BAT Current in Shutdown Mode

■

10-lead, low profi le (0.75 mm) 3mm × 3mm DFN

Output Range

BAT

(23μA) Burst Mode® Operation

CC

package

U

APPLICATIO S

■

Wireless Headsets

■

Bluetooth Applications

■

Portable MP3 Players

■

Multifunction Wristwatches

300mA Synchronous Buck

U

DESCRIPTIO

The LTC4081 is a complete constant-current/constant­voltage linear battery charger for a single-cell 4.2V
lithium-ion/polymer battery with an integrated 300mA
synchronous buck converter. A 3mm × 3mm DFN pack­age and low external component count make the LTC4081
especially suitable for portable applications. Furthermore,
the LTC4081 is specifi cally designed to work within USB
power specifi cations.

⎯C⎯H⎯R⎯

The
dropped to ten percent of its programmed value (C/10).
An internal 4.5 hour timer terminates the charge cycle.
The full-featured LTC4081 battery charger also includes
trickle charge, automatic recharge, soft-start (to limit inrush
current) and an NTC thermistor input used to monitor
battery temperature.

The LTC4081 integrates a synchronous buck converter
that is powered from the BAT pin. It has an adjustable
output voltage and can deliver up to 300mA of load cur­rent. The buck converter also features low-current high­effi ciency Burst Mode operation that can be selected by
the MODE pin.

The LTC4081 is available in a 10-lead, low profi le (0.75
mm) 3mm × 3mm DFN package.

, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation. All other
trademarks are the property of their respective owners. Protected by U.S. Patents,
including 6522118.

G pin indicates when charge current has

TYPICAL APPLICATIO

Li-Ion Battery Charger with 1.8V Buck Regulator

510Ω

V

CC

(3.75V

TO 5.5V)

100k

4.7μF

100k

V

CC

EN_BUCK

NTC

EN_CHRG

MODE

T

LTC4081

GND

CHRG

BAT

SW

FB

PROG

1OμH

806Ω

U

10pF

500mA

1M

806k

4081 TA01a

4.7μF

V

OUT

(1.8V/300mA)

4.7μF

+

4.2V
Li-Ion/
POLYMER
BATTERY

Buck Effi ciency vs Load Current

(V

= 1.8V)

OUT

100

EFFICIENCY

80

(Burst)

EFFICIENCY

60

40

EFFICIENCY (%)

20

0

0.01

(PWM)

0.1 10 1001 1000
LOAD CURRENT (mA)

POWER LOSS
(Burst)

POWER
LOSS
(PWM)

V

= 3.8V

BAT

= 1.8V

V

OUT

L = 10μH
C = 4.7μF

1000

100

10

1

0.1

0.01

4081 TA01b

POWER LOSS (mW)

4081f

1

LTC4081

WW

W

U

ABSOLUTE AXI U RATI GS

(Note 1)

VCC, t < 1ms and Duty Cycle < 1% .............. – 0.3V to 7V

Steady State ......................................... – 0.3V to 6V

V

CC

⎯C⎯H⎯R⎯

BAT,

⎯E⎯N⎯_⎯C⎯H⎯R⎯

MODE, EN_BUCK .......................... – 0.3V to V

G .................................................. – 0.3V to 6V

G, PROG, NTC ...................– 0.3V to VCC + 0.3V

+ 0.3V

BAT

FB ............................................................... – 0.3V to 2V

PIN CONFIGURATION

TOP VIEW

BAT

1

V

2

CC

EN_CHRG

PROG

NTC

10-LEAD (3mm × 3mm) PLASTIC DFN

= 110°C, θJA = 43°C/W (NOTE 3)

T

EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB

JMAX

3
4

5

DD PACKAGE

11

10

9
8
7
6

SW
EN_BUCK
MODE
FB
CHRG

BAT Short-Circuit Duration ............................ Continuous

BAT Pin Current ...................................................800mA

PROG Pin Current ....................................................2mA

Junction Temperature .......................................... .125°C

Operating Temperature Range (Note 2) .. – 40°C to 85°C

Storage Temperature Range .................. – 65°C to 125°C

ORDER INFORMATION

LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE

LTC4081EDD#PBF LTC4081EDD#TRPBF LDBX 10-Lead (3mm × 3mm) DFN 0°C to 70°C

Consult LTC Marketing for parts specifi ed with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based fi nish parts.

For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifi cations, go to: http://www.linear.com/tapeandreel/

The ● denotes specifi cations which apply over the full operating tempera-

ELECTRICAL CHARACTERISTICS

ture range, otherwise specifi cations are at TA = 25°C, VCC = 5V, V
(Note 2)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V

CC

V

BAT

I

CC

I

CC_SD

Battery Charger Supply Voltage (Note 4)

Input Voltage for the Switching
Regulator

Quiescent Supply Current (Charger On,
Switching Regulator Off)

Supply Current in Shutdown (Both
Battery Charger and Switching
Regulator Off)

(Note 5)

V

= 4.5V (Forces I

BAT

V

EN_BUCK

V

⎯E⎯N⎯_⎯C⎯H⎯R⎯

V

⎯E⎯N⎯_⎯C⎯H⎯R⎯

V

(4V)

BAT

= 0

= 5V, V

G

= 4V, V

G

= 3.8V, V

BAT

EN_BUCK
EN_BUCK

and I

BAT

= 0, VCC > V

= 0, V

⎯E⎯N⎯_⎯C⎯H⎯R⎯

PROG

CC

= 0V, V

G

= 0),

BAT

(3.5V) <

= 0V, V

NTC

●

●

●

●

EN_BUCK

3.75 5 5.5 V

2.7 3.8 4.5 V

= V

BAT

110 300 μA

5
2

, V

MODE

10 μA

= 0V.

μA

2

4081f

LTC4081

The ● denotes specifi cations which apply over the full operating tempera-

ELECTRICAL CHARACTERISTICS

ture range, otherwise specifi cations are at TA = 25°C, VCC = 5V, V
(Note 2)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

I

BAT_SD

Battery Charger

V

FLOAT

I

BAT

V

UVLO_CHRG

V

PROG

V

ASD

t

SS_CHRG

I

TRKL

V

TRKL

V

TRHYS

ΔV

RECHRG

ΔV

UVCL1,

ΔV

UVCL2

t

TIMER

I

C/10

T

LIM

R

ON_CHRG

f

BADBAT

D

BADBAT

I

NTC

V

COLD

V

HOT

V

DIS

f

NTC

D

NTC

Battery Current in Shutdown (Both
Battery Charger and Switching
Regulator Off)

V

Regulated Output Voltage I

BAT

Current Mode Charge Current R

VCC Undervoltage Lockout Voltage VCC Rising

PROG Pin Servo Voltage 0.8k ≤ R

Automatic Shutdown Threshold Voltage (VCC – V

Battery Charger Soft-Start Time 180 μs

Trickle Charge Current V

Trickle Charge Threshold Voltage V

Trickle Charge Threshold Voltage
Hysteresis

Recharge Battery Threshold Voltage V

(VCC – V

) Undervoltage Current

BAT

Limit Threshold Voltage

Charge Termination Timer

Recharge Time

Low-Battery Charge Time V

End of Charge Indication Current Level R

Junction Temperature in Constant­Temperature Mode

Power FET On-Resistance (Between

and BAT)

V

CC

Defective Battery Detection ⎯C⎯H⎯R⎯G Pulse
Frequency

Defective Battery Detection ⎯C⎯H⎯R⎯G Pulse
Frequency Duty Ratio

NTC Pin Current V

Cold Temperature Fault Threshold
Voltage

Hot Temperature Fault Threshold
Voltage

NTC Disable Threshold Voltage Falling Threshold; VCC = 5V

Fault Temperature ⎯C⎯H⎯R⎯G Pulse
Frequency

Fault Temperature ⎯C⎯H⎯R⎯G Pulse
Frequency Duty Ratio

V

⎯E⎯

⎯N⎯_⎯C⎯H⎯R⎯

G

V

⎯E⎯

⎯N⎯_⎯C⎯H⎯R⎯

G

V

(4V)

BAT

= 2mA

BAT

I

= 2mA, 4.3V < VCC < 5.5V

BAT

= 4k; Current Mode; V

PROG

R

= 0.8k; Current Mode; V

PROG

V

Falling

CC

PROG

BAT

(V

– V

CC

BAT

= 2V, R

BAT

Rising

BAT

– V

FLOAT

I

= 0.9 I

BAT

I

= 0.1 I

BAT

= 2.5V

BAT

= 2k (Note 6)

PROG

I

= 350mA, VCC = 4V 700 mΩ

BAT

V

= 2V 2 Hz

BAT

V

= 2V 75 %

BAT

= 2.5V 1 μA

NTC

Rising Voltage Threshold
Hysteresis

Falling Voltage Threshold
Hysteresis

Hysteresis

= 3.8V, V

BAT

= 5V, V

EN_BUCK

= 4V, V

EN_BUCK

≤ 4k

), VCC Low to High
), VCC High to Low

= 0.8k

PROG

⎯E⎯N⎯_⎯C⎯H⎯R⎯

= 0, V
= 0, V

> V

CC

(3.5V) <

CC

EN_BUCK

EN_BUCK

= 0V, V

G

BAT

= 0

= 0

NTC

●

= 0V, V

EN_BUCK

0.6

= V

BAT

2

4.179

4.158

●

●

90

475

●

●

3.5

2.8

●

●

0.98 1.0 1.02 V

60
15

35 50 65 mA

●

2.75 2.9 3.05 V

4.2

4.2

100
500

3.6

3.0

82
32

, V

MODE

5μA

4.221

4.242

110
525

3.7

3.2

100

45

100 150 350 mV

, 0°C < TA < 85°C 70 100 130 mV

BAT

CHG
CHG

180

90

●

3 4.5 6 hrs

●

1.5 2.25 3 hrs

●

0.75 1.125 1.5 hrs

●

0.085 0.1 0.115 mA/mA

300
130

115 °C

0.76 • V

CC

0.015 • V

0.017 • V

0.35 • V

CC

CC

CC

82
50

2Hz

25 %

= 0V.

μA

mA
mA

mV
mV

mV
mV

mV
mV

V
V

V
V

V
V

V
V

4081f

3

LTC4081

The ● denotes specifi cations which apply over the full operating tempera-

ELECTRICAL CHARACTERISTICS

ture range, otherwise specifi cations are at T
(Note 2)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

Buck Converter

V

FB

I

FB

f

OSC

I

BAT_NL_CF

I

BAT_NL_BM

I

BAT_SLP

V

UVLO_BUCK

R

ON_P

R

ON_N

I

LIM_P

I

LIM_N

I

ZERO_CF

I

PEAK

I

ZERO_BM

t

SS_BUCK

Logic

V

IH

V

IL

V

OL

I

IH

I

IL

R

⎯E⎯N⎯_⎯C⎯H⎯R⎯

G

I

⎯C⎯H⎯R⎯

G

Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.

Note 2: The LTC4081 is guaranteed to meet performance specifi cations
from 0°C to 85°C. Specifi cations over the –40°C to 85°C 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 ground plane will result in a thermal resistance much higher than
43°C/W.

FB Servo Voltage

FB Pin Input Current V

Switching Frequency

No-Load Battery Current (Continuous
Frequency Mode)

No-Load Battery Current (Burst Mode
Operation)

Battery Current in SLEEP Mode V

Buck Undervoltage Lockout Voltage V

PMOS Switch On-Resistance 0.95

NMOS Switch On-Resistance 0.85

PMOS Switch Current Limit

NMOS Switch Current Limit 700 mA

NMOS Zero Current in Normal Mode 15 mA

Peak Current in Burst Mode Operation MODE = V

Zero Current in Burst Mode Operation MODE = V

Buck Soft-Start Time From the Rising Edge of EN_BUCK to 90%

Input High Voltage

Input Low Voltage

Output Low Voltage (⎯C⎯H⎯R⎯G) I

Input Current High EN_BUCK, MODE Pins at 5.5V, V

Input Current Low

⎯E⎯N⎯_⎯C⎯H⎯R⎯

G Pin Input Resistance V

⎯⎯C⎯H⎯R⎯

G Pin Leakage Current V

= 25°C, VCC = 5V, V

A

= 0.85V –50 50 nA

FB

No-Load for Regulator, V
L = 10μH, C = 4.7μF

No-Load for Regulator, V
MODE = V

⎯E⎯N⎯_⎯C⎯H⎯R⎯

G

> Regulation Voltage

V

OUT

Rising

BAT

Falling

V

BAT

of Buck Regulated Output

⎯E⎯N⎯_⎯C⎯H⎯R⎯

G, EN_BUCK, MODE Pin Low to High

⎯E⎯N⎯_⎯C⎯H⎯R⎯

G, EN_BUCK, MODE Pin High to Low

= 5mA

SINK

⎯E⎯N⎯_⎯C⎯H⎯R⎯

G, EN_BUCK, MODE Pins at GND

⎯E⎯N⎯_⎯C⎯H⎯R⎯

G

= 4.5V, V

BAT

= 3.8V, V

BAT

⎯E⎯N⎯_⎯C⎯H⎯R⎯

, L = 10μH, C = 4.7μF

BAT

⎯E⎯N⎯_⎯C⎯H⎯R⎯

= 5V, MODE = V

BAT

BAT

= 5V

= 5V

⎯C⎯H⎯R⎯

G

Note 4: Although the LTC4081 charger functions properly at 3.75V, full
charge current requires an input voltage greater than the desired fi nal
battery voltage per ΔV

Note 5: The 2.8V maximum buck undervoltage lockout (V
threshold must fi rst be exceeded before the minimum V
applies.

Note 6: I
with indicated PROG resistor.

⎯E⎯N⎯_⎯C⎯H⎯R⎯

BAT

= 0V, V

G

= 5V,

G

= 5V,

G

,

= 0V, V

NTC

●

●

EN_BUCK

0.78 0.80 0.82 V

1.8 2.25 2.75 MHz

= V

BAT

1.9 mA

23 μA

●

10 15 20 μA

●

2.6

●

2.4

375 520 700 mA

2.7

2.5

, V

MODE

2.8

2.6

50 100 150 mA

20 35 50 mA

400 μs

●

●

0.4 V

●

UVCL1

●

–1 1 μA

●

–1 1 μA

1 1.45 3.3 MΩ

●

specifi cation.

= 5V

BAT

is expressed as a fraction of measured full charge current

C/10

60 105 mV

1.2 V

1μA

UVLO_BUCK

specifi cation

BAT

= 0V.

Ω

Ω

) exit

V
V

4

4081f

TYPICAL PERFORMANCE CHARACTERISTICS

(TA = 25°C, VCC = 5V, V
specifi ed)

LTC4081

= 3.8V, unless otherwise

BAT

Battery Regulation (Float) Voltage
vs Charge Current

4.21
R

= 2k

PROG

4.20

4.19

4.18

4.17

4.16

FLOAT VOLTAGE (V)

4.15

4.14

4.13

0

50 100

CHARGE CURRENT (mA)

150

Charge Current vs Temperature
with Thermal Regulation
(Constant-Current Mode)

250

VCC = 6V

= 3V

V

BAT

= 2k

R

PROG

200

150

100

CHARGE CURRENT (mA)

50

0

–50

THERMAL CONTROL
LOOP IN OPERATION

0–25 50

25 75

TEMPERATURE (°C)

⎯E⎯N⎯_⎯C⎯H⎯R⎯

MODE Pin Threshold Voltage
vs Temperature

0.95

0.90

0.85

0.80

0.75

0.70

0.65

THRESHOLD VOLTAGE (V)

0.60

0.55

0.50
–50

200 250

4081 G01

125

100

4081 G04

G, EN_BUCK and

RISING

–10

–30

10 90

TEMPERATURE (°

Battery Regulation (Float) Voltage
vs Temperature

4.210

4.205

4.200

4.195

4.190

4.185

4.180

FLOAT VOLTAGE (V)

4.175

4.170

4.165

4.160
–30 –10 30

–50

10

TEMPERATURE (°C)

PROG Pin Voltage
vs Charge Current

1.0
R

= 2k

PROG

0.8

0.6

(V)

PROG

V

0.4

0.2

0

25

FALLING

30

0

50 70

C)

75

100

CHARGE CURRENT (mA)

4081 G07

50 70 90

12550

150

PULLDOWN RESISTANCE (MΩ)

Battery Regulation (Float) Voltage
vs VCC Supply Voltage

4.25

4.20

4.15

4.10

4.05

4.00

FLOAT VOLTAGE (V)

3.95

3.90

3.85
4

4081 G02

Charger FET On-Resistance
vs Temperature

0.9
VCC = 4V

I

0.8

BAT

0.7

0.6

(Ω)

0.5

0.4

DS(ON)

R

0.3

0.2

0.1

0

175

200

4081 G05

⎯E⎯N⎯_⎯C⎯H⎯R⎯

–50

G Pin Pulldown

Resistance vs Temperature

1.7

1.6

1.5

1.4

1.3

1.2

1.1

1.0
–50

–10

–30

TEMPERATURE (°C)

10 90

30

4.5 5
VCC SUPPLY VOLTAGE (V)

= 350mA

–30 –10 30

10

TEMPERATURE (°C)

50 70

4081 G08

5.5

4081 G03

50 70 90

4081 G06

6

4081f

5

LTC4081

TYPICAL PERFORMANCE CHARACTERISTICS

(TA = 25°C, VCC = 5V, V
specifi ed)

⎯C⎯H⎯R⎯

G Pin Output

Low Voltage vs Temperature

80

I

= 5mA

CHRG

70

60

50

40

30

VOLTAGE (mV)

20

10

Normalized Charge Termination
Time vs Temperature

1.05

1.00

0.95

0.90

NORMALIZED TIMER PERIOD

0.85

Buck Oscillator Frequency
vs Battery Voltage

2.28

2.27

2.26

2.25

2.24

FREQUENCY (MHz)

2.23

= 3.8V, unless otherwise

BAT

0

–50

–30

–10

10 90

TEMPERATURE (°

Buck Oscillator Frequency
vs Temperature

2.4

V

= 3.8V

BAT

2.3

2.2

2.1

2.0

FREQUENCY (MHz)

1.9

1.8
–60

–20 20

–40 0

TEMPERATURE (°C)

Buck Output Voltage
vs Battery Voltage

1.810
I

= 1mA

OUT

SET FOR 1.8V

V

OUT

1.805

1.800

1.795

1.790

BUCK OUTPUT VOLTAGE (V)

1.785

30

V

BAT

50 70

C)

V

= 4.5V

BAT

= 2.7V

60

40

Burst Mode
OPERATION

PWM MODE

2.22

2.5

Buck Effi ciency vs Load Current
(V

OUT

100

EFFICIENCY

80

POWER LOSS (mW)

(BURST)

60

40

EFFICIENCY (%)

20

0

0.01

3.0 3.5 4.5
BATTERY VOLTAGE (V)

4.0

4081 G11

= 1.5V)

EFFICIENCY
(PWM)

POWER LOSS
(BURST)

0.1 10 1001 1000
LOAD CURRENT (mA)

POWER
LOSS
(PWM)

V

= 3.8V

BAT

= 1.5V

V

OUT

L = 10μH
C = 4.7μF

4081 G13a

1000

100

POWER LOSS (mW)

10

1

0.1

0.01

4081 G09

0.80
–50

–30

–10

10 90

30

50 70

TEMPERATURE (°C)

4081 G10

Buck Effi ciency vs Load Current
(V

= 1.8V)

OUT

100

EFFICIENCY

80

(BURST)

60

40

EFFICIENCY (%)

20

100

80

4081 G12

0

0.01

EFFICIENCY
(PWM)

POWER LOSS
(BURST)

V

BAT

V

OUT

L = 10μH
C = 4.7μF

0.1 10 1001 1000
LOAD CURRENT (mA)

POWER
LOSS
(PWM)

= 3.8V
= 1.8V

4081 G13

1000

100

10

1

0.1

0.01

No-Load Buck Input Current
Buck Output Voltage
vs Temperature

1.810
I

= 1mA

OUT

SET FOR 1.8V

V

OUT

1.805

1.800

1.795

1.790

BUCK OUTPUT VOLTAGE (V)

1.785

Burst Mode
OPERATION

PWM MODE

(Burst Mode Operation)
vs Battery Voltage

35

I

= 1mA

OUT

= 1.8V

V

OUT

30

L = 10μH

25

20

15

10

BUCK INPUT CURRENT (μA)

5

6

1.780

2.5

3.0 3.5 4.0 4.5
BATTERY VOLTAGE (V)

4081 G14

1.780
–50

–30 –10

30 70 90

10 50

TEMPERATURE (˚C)

4081 G15

0

2.5

3.0

3.5

BATTERY VOLTAGE (V)

4.0

4.5

4081 G16

4081f

TYPICAL PERFORMANCE CHARACTERISTICS

(TA = 25°C, VCC = 5V, V
specifi ed)

No-Load Buck Input Current
(Burst Mode Operation)
vs Temperature

35

L = 10μH
C = 4.7μF

30

= 1.8V

V

OUT

25

20

15

10

NO LOAD INPUT CURRENT (μA)

5

V

= 4.2V

BAT

V

= 3.8V

BAT

V

= 2.7V

BAT

Buck Main Switch (PMOS)
On-Resistance vs Battery Voltage

1.2

1.0

0.8

0.6

0.4

ON-RESISTANCE (Ω)

0.2

Buck Main Switch (PMOS)
On-Resistance vs Temperature

1.2

1.0

0.8

0.6

0.4

ON-RESISTANCE (Ω)

0.2

LTC4081

= 3.8V, unless otherwise

BAT

0

–50 10 50

–30 –10

TEMPERATURE (˚C)

30 70 90

Buck Synchronous Switch (NMOS)
On-Resistance vs Battery Voltage

1.2

1.0

0.8

0.6

0.4

ON-RESISTANCE (Ω)

0.2

0

2.5

Maximum Output Current
(PWM Mode) vs Battery Voltage

500

L = 10μH

400

300

200

MAXIMUM OUTPUT CURRENT (mA)

100

2.7 4.23 3.6

4081 G18

3.5

3.0
BATTERY VOLTAGE (V)

V

OUT

3.3 3.9 4.5

BATTERY VOLTAGE (V)

4.0

SET FOR 1.8V

0

2.5

4.5 5.0

4081 G21

4081 G23

3.5

3.0
BATTERY VOLTAGE (V)

4.5 5.0

4.0

4081 G19

Buck Synchronous Switch (NMOS)
On-Resistance vs Temperature

1.2

1.0

0.8

0.6

0.4

ON-RESISTANCE (Ω)

0.2

0

–50 10 50

–30 –10

Maximum Output Current (Burst
Mode Operation) vs Battery Voltage

80

L = 10μH

70

60

50

40

30

20

MAXIMUM OUTPUT CURRENT (mA)

10

0

2.7 4.23 3.63.3 3.9 4.5
BATTERY VOLTAGE (V)

0

–50 10 50

–30 –10

TEMPERATURE (°C)

30 70 90

TEMPERATURE (°C)

V

SET FOR 1.8V

OUT

30 70 90

4081 G20

4081 G22

4081 G24

4081f

7

LTC4081

TYPICAL PERFORMANCE CHARACTERISTICS

(TA = 25°C, VCC = 5V, V
specifi ed)

= 3.8V, unless otherwise

BAT

V

OUT

20mV/DIV

AC COUPLED

I

LOAD

250mA/DIV

0mA

Output Voltage Transient
Step Response (PWM Mode)

50μs/DIV

1V/DIV

V

EN_BUCK

5V/DIV

V

OUT

Buck V
(I

0V

0V

LOAD

Soft-Start

OUT

= 50mA)

4081 G25

200μs/DIV

V

OUT

50mV/DIV

AC COUPLED

V

MODE

5V/DIV

Output Voltage Waveform
when Switching Between Burst
and PWM Mode (I

0V

50μs/DIV

4081 G28

LOAD

200mV/DIV

= 10mA)

V

PROG

4081 G27

Charger V

0V

V

OUT

20mV/DIV

AC COUPLED

I

LOAD

50mA/DIV

0mA

PROG

50μs/DIV

Output Voltage Transient
Step Response (Burst Mode
Operation)

50μs/DIV

Soft-Start

4081 G29

4081 G26

8

4081f