LTC1980_1_技术文档

LTC1980

Combination Battery

Charger and DC/DC Converter

U

FEATURES

DESCRIPTIO

The LTC^®1980 integrates PWM power control for charg-

ing a battery and converting the battery voltage to a

regulated output or simultaneously charging the battery

whilepoweringasystemloadfromanunregulatedACwall

adapter. Combining these features into a single IC pro-

duces a smaller area and lower cost solution compared to

presentlyavailablemulti-ICsolutions.TheLTC1980shares

the discrete components for both the battery charger and

theDC/DCconverterthusminimizingsizeandcostrelative

to dual controller solutions. Both the battery charger and

DC/DC converter use a current mode flyback topology for

high efficiency and excellent transient response. Optional

BurstModeoperationandpower-downmodeallowpower

density, efficiency and output ripple to be tailored to the

application.

■

Single Controller IC Includes Battery Charger

Plus DC/DC Converter

■

Wall Adapter Voltage May be Above or Below

Battery Voltage

■

LDO Controller Allows Simultaneous Charging

and Regulating from Wall Adapter Input

■

Standalone Li-Ion Battery Charger Including Charge

Termination, Overvoltage Protection, Shorted-Cell

Detection and Battery Recharge

■

Selectable 4.1V, 4.2V, 8.2V and 8.4V Float Voltages

Simple NiMH and NiCd Battery Charger

Pin Programmable Regulator Burst Mode^®Operation

and Shutdown for High Efficiency

High Efficiency Current Mode 300kHz PWM

Reduced Component Architecture

Undervoltage Protection and Soft-Start Ensures

Start-Up with Current Limited Wall Adapter

Small 24-Pin SSOP Package

■

The LTC1980 provides a complete Li-Ion battery charger

with charge termination timer, preset Li-Ion battery volt-

ages, overvoltage and undervoltage protection, and user-

programmableconstant-currentcharging.Automaticbat-

tery recharging, shorted-cell detection, and open-drain

C/10 and wall plug detect outputs are also provided. User

programming allows NiMH and NiCd battery chemistries

to be charged as well.

■

U

APPLICATIO S

■

Digital Cameras

■

Handheld Computers

■

Personal Digital Assistants

1W to 10W Uninterruptable Power Supplies

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

Burst Mode is a registered trademark of Linear Technology Corporation.

Patents Pending.

■

U

TYPICAL APPLICATIO

Li-Ion Charger and DC/DC Converter Using One IC

3.3V Regulator Efficiency vs Load Current

POWER FLOW

90

CHARGING

BATTERY

OPERATION

UNREGULATED

85

80

75

70

65

60

WALL ADAPTER

Li-Ion

BATTERY

•

INPUT (3V TO 10V)

SYSTEM

POWER

BAT-FET

REG-FET

•

LDO/

SWITCH

V

A

FIGURE 5

= 3.6V

3.3V

1.8V

1.5V

BAT

= 25°C

SYSTEM LOAD

T

DC/DC

CONVERTERS

10

100

1000

LTC1980

LOAD CURRENT (mA)

1980 TA01

1980 G04

1980f

1

LTC1980

W W

U W

U

ABSOLUTE AXI U RATI GS

PACKAGE/ORDER I FOR ATIO

(Note 1)

V_REGto GND ............................................. –0.5V to 12V

V_BATto GND ............................................. –0.5V to 12V

PROG, I_SENSE.............................................. –0.5V to 5V

PROGT, REGFB, V_C, BATT1, BATT2

TIMER, SS ............................................ –0.5V to V_BIAS2

LDOFB, LDODRV .................................... –0.5V to V_REG

WA, V_BIAS1, REG....................................... –0.5V to 12V

MODE ................................................... –0.5V to V_BIAS1

V_BIAS2......................................................... –0.5V to 5V

OVP ............................................................ –0.5V to 5V

PGND to GND .................................... Connect Together

Operating Ambient Temperature Range

ORDER PART

NUMBER

TOP VIEW

PROG

PROGT

REGFB

1

2

3

4

5

6

7

8

9

SS

24

23

22

21

20

19

18

17

16

15

14

13

OVP

CAOUT

LTC1980EGN

V

C

I

SENSE

LDOFB

GND

LDODRV

V

BIAS2

V

REG

BAT

WA

TIMER

MODE

REG

BATT1

BATT2 10

RGTDR 11

PGND 12

BGTDR

V

BIAS1

(Note 2) ................................................. –40°C to 85°C

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

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

GN PACKAGE

24-LEAD NARROW PLASTIC SSOP

T_JMAX= 125°C, θ_JA= 85°C/W

Consult LTC Marketing for parts specified with wider operating temperature ranges.

ELECTRICAL CHARACTERISTICS

The ● denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at T_A= 25°C. V_BAT= 2.4V, V_REG= 5V, V_BATunloaded.

SYMBOL

PARAMETER

CONDITIONS

MIN

2.85

TYP

MAX

10

UNITS

V

Positive Supply Voltage, V

Feedback Voltage

V

BAT

REG

BAT

2.85

10

REG

REGFB Tied to V

●

1.194

1.225 1.256

0.75

V

FB

C

Voltage on PROGT Pin

Burst Mode Operation

Supply Current, Quiescent, V

PROGT Tied to V

V

PROGT

BURST

C

I

Regulator Mode, REGFB = 1.5V

mA

REG

I

Supply Current, Quiescent, V

Regulator Mode, REGFB = 0V

Mode = 0V

2

4.3

15

mA

µA

V

HIGH

Supply Current in Shutdown Mode, V

SHDN

REG

V

Positive-Going Undervoltage Lockout Voltage

Undervoltage Lockout Hysteresis

From Either V

or V

2.45

2.7

100

10

2.85

UVL

BAT

REG

mV

µA

V

UVHYS

I

Soft-Start Ramp Current

BATT1 = 0, BATT2 = 0, Charger Mode

BATT1 = 0, BATT2 = 0

SS

V

Output Float Voltage in Constant Voltage Mode

●

4.059

4.158

8.118

8.316

1.207

4.1

4.2

8.2

8.4

4.141

4.242

8.282

8.484

FLOAT0

FLOAT1

FLOAT2

FLOAT3

FLOAT4

BATT1 = 1, BATT2 = 0

V

BATT1 = 0, BATT2 = 1 (Note 3)

BATT1 = 1, BATT2 = 1 (Note 3)

V

BATT1 = Open, BATT2 = Don’t Care

Measured from OVP Input

1.225 1.243

V

Recharge Threshold, Delta Voltage with Respect

to Float Voltage

BATT2 = 0, BATT1 = 0 or 1

200

400

mV

RCHG0

Recharge Threshold, Delta Voltage with Respect

to Float Voltage

BATT2 = 1, BATT1 = 0 or 1

RCHG1

1980f

2

LTC1980

ELECTRICAL CHARACTERISTICS

The ● denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at T_A= 25°C. V_BAT= 2.4V, V_REG= 5V, V_BATunloaded.

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

V

Recharge Threshold, Delta Voltage with Respect

to Float Voltage, Measured at OVP

BATT 1 = Open

60

mV

RCHG2

V

Charger Shorted Cell Threshold

BATT2 = 0

2.55

5.2

2.7

5.4

1.0

350

2.8

V

LT0

LT1

Charger Shorted Cell Threshold

BATT2 = 1

5.65

V

I

Input Bias Current, Low Dropout Regulator

Transconductance, Low Dropout Regulator

Output Low Voltage, Low Dropout Regulator

Output High Voltage, Low Dropout Regulator

Low Dropout Regulator Output Current, Source/Sink

Error Amplifier Open-Loop Voltage Gain

Error Amplifier Input Bias Current

Measured at LDOFB Pin

Measured from LDOFB to LDODRV

µA

BLDO

g

µmhos

mldo

V

0.1

V

OLLDO

OHLDO

OUTLDO

V

– 0.1

REG

I

±20

µA

dB

µA

V

A

From REGFB to V

SS = Open

60

VOL

BEA

C

I

–0.1

0

0.1

0.5

2

V

Error Amplifier Output Low Voltage

OLEA

OHEA

OUT

Error Amplifier Output High Voltage

1.4

V

I

Error Amplifier Output Source Current

Error Amplifier Output Sink Current

0.5

–1.2

mA

g

Float Voltage Error Amplifier Transconductance

Measured from OVP to SS,

Charger Mode, BATT1 = Open

65

µmhos

mflt

I

Float Voltage Error Amplifier Input Current

(Measured at OVP Input)

–0.1

–6

0.1

6

µA

BFLT

V

Current Amplifier Offset Voltage

mV

µA

OS1

VCA

I

Input Bias Current, I

Input

–100

2.44

BIS

SENSE

A

Current Amplifier Voltage Gain

Measured from I

CAOUT Pin

to

2.3

2.55

V/V

SENSE

R

PROG Pin On Resistance

PROG Pin Leakage Current

Switching Frequency

400

100

300

10

Ω

nA

kHz

ns

kHz

µA

Ω

PROG

S

I

f

●

260

340

t , t

r

Driver Output Transition Times

Driver Output Break Times

Timer Frequency

C = 15pF

L

f

t

f

I

V

= V = 10V

REG

100

4.5

–4

BREAK

TIMER

TIMER1

TIMER2

BAT

C = 1000pF

TIMER Pin Source Current

TIMER Pin Sink Current

REG On Resistance

4

R

REG

68

I

REG Pull-Down Current

REG Leakage Current

2

5

9

µA

nA

V

REGPD

REGLK

60

V

REG Logic Threshold

0.3

1.3

VTHREG

IL1

Digital Input Low Voltage,

Negative-Going, Wall Adapter (WA)

V

= 5V

1.185

1.221 1.247

1.226 1.257

100

V

REG

V

Digital Input High Voltage,

Positive-Going, Wall Adapter (WA)

1.195

V

IH1

V

Digital Input Low Voltage, BATT1

Digital Input High Voltage, BATT1

mV

V

IL2

IH2

V

BIAS2

–100

1980f

3

LTC1980

ELECTRICAL CHARACTERISTICS

The ● denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at T_A= 25°C.V_BAT= 2.4V, V_REG= 5V, V_BATunloaded.

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

V

Digital Input Pull-Up Voltage, BATT1

Digital Input Low Voltage, BATT2

Digital Input High Voltage, BATT2

Digital Input Current, WA

BATT1 Input Floating

1.6

P2

0.3

V

IL3

IH3

2

V

I

–5

5

10

1

µA

I1

Digital Input Current, BATT1

Digital Input Current, BATT2

–10

–1

I2

I3

Note 1: Absolute Maximum Ratings are those values beyond which the life

of a device may be impaired.

temperature range are assured by design, characterization and correlation

with statistical process controls.

Note 2: The LTC1980E is guaranteed to meet performance specifications

from 0°C to 70°C. Specifications over the –40°C to 85°C operating

Note 3: T = 0°C to 70°C.

A

U W

TYPICAL PERFOR A CE CHARACTERISTICS

Feedback Reference Voltage

vs Temperature

Switching Frequency Variance

vs Temperature

Regulator Load Regulation

1.5

1.0

0

–0.2

–0.4

–0.6

–0.8

–1.0

–1.2

1.2240

1.2235

1.2230

1.2225

1.2220

1.2215

1.2210

1.2205

V

A

= 4.2V

BAT

REG

≅ 3.3V

T

= 25°C

FIGURE 5

0.5

0

–0.5

–1.0

–1.5

–40

–15

10

35

60

85

–40

–15

10

35

60

85

0

100

200

300

400

500

TEMPERATURE (°C)

LOAD CURRENT (mA)

1980 G02

1980 G03

1980 G01

3.3V Regulator Efficiency

vs Load Current

5V Regulator Efficiency

vs Load Current

Regulator Load Step Response

90

85

80

75

70

65

60

90

85

80

75

70

65

60

V

REG

50mV/DIV

I

L

500mA/DIV

V

T

= 3.6V

BAT

A

1980 G06

V

= 3.6V

100µs/DIV

BAT

REG

= 25°C

V

A

FIGURE 5

= 3.6V

BAT

= 25°C

≅ 3.3V

R8 = 309k

FIGURE 5

T

I

= 100mA TO 500mA

= 25°C

L

T

A

FIGURE 5

10

100

1000

10

100

1000

LOAD CURRENT (mA)

1980 G04

1980 G05

1980f

4

LTC1980

U W

TYPICAL PERFOR A CE CHARACTERISTICS

Typical BGTDR and RGTDR

Waveforms

Typical I_SENSEWaveforms,

Regulator

Typical Operation with Burst

Mode Operation Disabled

V

REG

BGTDR

1V/DIV

50mV/DIV

I

SENSE

20mV/DIV

PIN 21

FIGURE 5

I

SENSE

RGTDR

1V/DIV

50mV/DIV

1980 G07

1980 G08

1980 G09

V

T

= 3.6V

= 3.3V

1µs/DIV

V

I

= 3.6V

= 3.3V

1µs/DIV

V

I

= 3.6V

1µs/DIV

BAT

REG

A

BAT

REG

L

BAT

REG

L

≅ 3.3V

= 25°C

= 500mA

I

= 500mA

T

= 25°C

MODE = V

= 25°C

L

A

BIAS1

FIGURE 5

T

A

FIGURE 5

Regulator Output Transient

Response—Wall Adapter “Hot

Plugged”

Regulator Output Transient

Response—Wall Adapter Removal

Burst Mode Circuit Operation

V

REG

V

50mV/DIV

V

REG

1V/DIV

REG

1V/DIV

V

BGTDR

2V/DIV

LDO

V

LDO

0.5V/DIV

0.1V/DIV

1980 G11

1980 G10

1980 G12

V

I

= 3.6V

= 3.3V

500µs/DIV

V

I

= 3.6V

= 3.3V

200µs/DIV

V

I

= 3.6V

= 3.3V

500µs/DIV

BAT

REG

LDO

BAT

REG

L

BAT

REG

LDO

= 3.1V

= 10mA

= 3.1V

= 200mA

WALL ADAPTER

= 25°C

T

= 25°C

= 200mA

LDO

A

LDO

V

T

= 6V TO 0V

FIGURE 5

V

T

= 0V TO 6V

WALL ADAPTER

= 25°C

A

FIGURE 5

Typical C_TIMERWaveform

Mode Pin Input Current vs V_IN

1.5

1.0

V

T

= 2.4V

= 5V

BAT

REG

= 25°C

A

0.5

TIMER

100mV/DIV

PIN 17

0

–0.5

–1.0

–1.5

1980 G14

C

A

= 0.24µF 5ms/DIV

TIMER

T

= 25°C

0

1.0

1.5

2.0

2.5

3.0

0.5

MODE PIN V (V)

IN

1980 G13

1980f

5

LTC1980

U

PI FU CTIO S

PROG (Pin 1): Charge Current Ratio Programming Pin.

Programsthefullchargecurrentwhenthechargerisinthe

constant current mode. A resistor placed between the

PROG pin and the PROGT pin (Pin 2) determines the

charge current. The PROG pin connects to an open drain

MOSFET which turns on for full current and is off when

trickle charging.

V_REG(Pin 7): Connection Point to the DC/DC Converter

Side of the Combo Charger/Converter Circuit.

WA (Pin 8): Wall Adapter Comparator Input. An external

resistor divider from the wall adapter output to WA to

ground sets the threshold which determines if charging

can occur. If the wall adapter is below this threshold, the

LTC1980 assumes the wall adapter is not present and the

charger shuts down. Wall adapter sense threshold is set

higher than the DC/DC converter output voltage to insure

correct operation.

PROGT (Pin 2): Trickle Charge Programming Pin. Pro-

grams the trickle charge current for a deeply discharged

battery. Two resistors are used, one between the PROGT

pin and CA_OUT(Pin 22) and another from PROGT to

ground. A capacitor between the PROGT pin and V_C(Pin

4) provides compensation for the constant current feed-

back loop.

BATT1 (Pin 9): Logic Input Pin for Selecting

Preprogrammed Li-Ion Charge Voltage. See Truth Table

logic settings.

BATT2 (Pin 10): Logic Input Pin for Selecting

Preprogrammed Li-Ion Charge Voltage. The following

combinations of BATT1 and BATT2 select the correct Li-

Ion charge voltage. See Truth Table.

REGFB (Pin 3): DC/DC Converter Feedback Pin. This pin is

usedtoprogramtheDC/DCconverteroutputvoltagewhen

the LTC1980 is in the DC/DC (regulator) converter mode.

AnexternalresistordividerfromV_REGtoREGFBtoground

programstheoutputvoltage. Thevirtualreferencevoltage

(V_REF) on this pin is 1.225V. A series RC from the REGFB

pin to V_C(Pin 4) provides pole-zero compensation for the

regulator outer loop.

BATT2

BATT1

FLOAT VOLTAGE

0

4.1V

0

1

4.2V

1

0

8.2V

8.4V

1

Open

V_C(Pin 4): Control Signal of the Inner Loop of the Current

Mode PWM. A common current mode loop is used by the

batterychargerandvoltageregulatorfunctions. Minimum

duty factor (measured on BGTDR (Pin 14) in regulator

mode and RGTDR (Pin 11) in charger mode) occurs at

approximately 1V. Duty factor increases as V_Cincreases.

This part includes slope compensation, so there is some

variation in V_Cfor minimum and maximum duty factor as

V_REGor V_BATis varied.

Don’t Care

Externally Set Via OVP

Logic 1 = V

(Pin 19), Logic 0 = GND

BIAS2

RGTDR (Pin 11): DC/DC Converter (Regulator) Side Gate

Drive Pin. This pin provides gate drive to the external

MOSFET (REG-FET) that connects to V_REGvia the trans-

former.

PGND (Pin 12): Power Ground. Refer to the Applications

Information section for proper use of ground and power

ground connections.

LDOFB (Pin 5): Low Dropout Regulator Feedback Pin.

This pin is used to program the low dropout linear regula-

tor output voltage. An external resistor divider from the

outputoftheLDOregulator(drainoftheexternalMOSFET)

to LDOFB to ground programs the output voltage. The

virtual reference voltage on this pin is 1.225V.

V_BIAS1(Pin 13): Internally Generated Power Bus. Bypass

thispinwitha1µForlargerceramiccapacitor(orotherlow

ESR capacitor) to PGND (Pin 12). Do not connect any load

to this pin.

BGTDR (Pin 14): DC/DC Converter (Battery) Side Gate

Drive Pin. This pin provides gate drive to the external

MOSFET (BAT-FET) that connects to V_BATvia the trans-

former.

LDODRV (Pin 6): Low Dropout Error Amplifier Output.

This pin drives the gate of an external PMOS pass transis-

tor. This pin is pulled up to V_REG(shutting off the pass

transistor)ifMODE(Pin16)isgroundedorifundervoltage

occurs.

1980f

6

LTC1980

U

PI FU CTIO S

REG(Pin15):BidirectionalRegulatorModeControlPin. A

pull-up resistor is required between this pin and V_BIAS2

This pin is open when charging normally, has a weak pull-

down (approximately 5µA) when conditioning the battery

and a strong pull-down when in regulator mode. Pulling

this pin low forces the IC into regulator mode.

I_SENSE(Pin 21): Current Sense Input Pin. Connects inter-

nally to a current amplifier and zero current comparator.

This pin should Kelvin-connect to the current sense resis-

tor (R_SENSE) .

.

CAOUT (Pin 22): Current Amplifier Output. A program

resistor connects between this pin and PROGT (Pin 2) to

set the charge current (in constant-current mode).

MODE (Pin 16): Selects different operating modes in both

charger and DC/DC converter configurations. Also en-

ables and disables Burst Mode operation. See Mode Pin

Operation table in Application section.

OVP (Pin 23): Overvoltage Protection. This pin connects

to the tap on an optional external voltage divider con-

nected across the battery. This allows nonstandard float

voltages to be used for the battery charger. Overvoltage,

restart and undervoltage thresholds will also be affected

by the external voltage division ratio. To use this pin,

BATT1 (Pin 9) must float.

TIMER (Pin 17): A timing capacitor on this pin determines

the normal charge time for charge termination.

C(µF) = 0.25 • Time (Hours)

V

_BAT(Pin18): Thispinconnectstothepositiveterminalof

SS (Pin 24): Soft-Start. A capacitor between this pin and

ground sets the battery charge ramp rate. Battery charge

currentisverylowthemomentaftertheconverterswitches

fromDC/DCconverter(regulator)modetobatterycharger

mode then ramps up to final battery charge current from

there.Thisinsuresthatthewalladapterisnotloadeddown

with a large inrush current that could prevent correct

battery charger operation.

the battery and the battery side of the power converter.

V_BIAS2(Pin 19): Internally Generated Voltage. Bypass this

pin with a 1µF or larger ceramic capacitor (or other low

ESR capacitor). Do not connect any load to this pin.

GND (Pin 20): Signal Ground. This pin should Kelvin-

connect to the current sense resistor (R_SENSE).

The same capacitor, which sets the soft-start ramp rate,

also sets the compensation for the battery float voltage

control loop.

1980f

7

LTC1980

W

BLOCK DIAGRA

LDOFB

5

V

LDODRV

6

CAOUT

22

BIAS1

13

REF_UVL

I

21

SENSE

V

REF

REFERENCE

+

–

+

I = O

COMP

–

GM

V

BAT 18

V

REF

MAX

V

+

–

REF

UVL

V

REG

–

+

–

+

DD

V

REG

7

V

REF

V

19

SR_EN

BIAS2

DIS

L

H

DUMP

XFMR

V

M

REF

MODE 16

MODE

S

R

H = BURST MODE OPERATION OFF

OPEN = BURST MODE OPERATION ON

L = DISABLE

RGTDR

BGTDR

11

14

12

OSC

Q

RAMP

+

–

V

4

REG

V

PWM

COMP

C

AC

V

BAT

PGND

PROGT

REGFB

2

3

AC

SLEEP

V

+

–

REF

EA

WAKE

+

–

BATT1

9

BURST

V

+

REF

CONDITION BATTERY

OVP 23

–

10

BATT2

V

+

REF

RECHARGE

START

TIMEOUT

TIMER

SHORT CYCLE

–

17 TIMER

V

REF

+

–

8

WA

5µA

1

PROG

15

REG

V

+

–

REF

GM

20

GND

REG

24

1980 BD

SS

1980f

8

LTC1980

U

OPERATIO

The LTC1980 is an IC designed to provide a regulated

voltage to a system load from an unregulated or regulated

wall adapter, or from a battery and also charge a battery,

therebyprovidinganuninterruptablepowersourceforthe

system. When the wall adapter is present it provides

power to the system load and, if needed, a portion of the

power can be used to simultaneously charge the battery.

If the wall adapter is removed, the LTC1980 uses the

battery as a power source to continue providing a regu-

lated output voltage to power the system.

(Figure 1). The unique bidirectional power converter to-

pology (Figure 2) accounts for much of the area savings.

A transformer based design allows the wall adapter volt-

age to be less than or greater than the battery voltage.

The LTC1980 includes a 300kHz DC/DC PWM converter

thatoperatesintwomodes.Thefirstmodeiswhenthewall

adapter is present and the LTC1980 is used to charge the

battery using a constant-current/constant-voltage charge

scheme. The second mode is when the wall adapter is

removed and the battery powers the LTC1980 and the

DC/DC converter generates a regulated output voltage.

Combining these two functions into a single IC reduces

circuit area compared to presently available solutions

Existing Methods

CHARGE

TERMINATION

Using the LTC1980

BATTERY

CHARGER

FROM

WALL ADAPTER

FROM WALL ADAPTER

LTC1980-BASED

POWER DESIGN

TO SYSTEM LOAD

DC/DC CONVERTERS

POWER ROUTING

LOW DROPOUT

TO SYSTEM LOAD

DC/DC CONVERTERS

1980 F01

REGULATOR

PWM

REGULATOR

Figure 1. Portable Power Systems

WALL

ADAPTER

T1

•

T1

•

Li-Ion

BATTERY

Li-Ion

BATTERY

REG-FET

BAT-FET

REG-FET

•

SYSTEM LOAD

DC/DC

CONVERTERS

SYSTEM LOAD

DC/DC

CONVERTERS

R

S

I

SENSE

LTC1980

1980 F02a

(a) Battery Charger Mode

(b) DC/DC Converter Mode (Wall Adapter Removed)

Figure 2. LTC1980 Bidirectional Power Conversion

1980f

9

LTC1980

U

OPERATIO

Lithium-Ion Battery Charger Operation

will maintain the programmed preset float voltage across

the battery until the timer terminates the charge cycle.

During trickle charging, if the battery voltage remains

below 2.7V for 1/4 of the total programmed charge time,

the battery may be defective and the charge cycle ends.

Also, if a battery open circuit is detected, the charge cycle

ends immediately. The charger can be shut down by

pulling the REG pin low, although the timer will continue

until it times out.

With the wall adapter power applied, the LTC1980 oper-

ates as a constant-current/constant-voltage PWM battery

charger, with a portion of the adapter current used for

charging and the rest flowing to the system load through

an optional low dropout regulator.

A charge cycle begins when the voltage at V_REGexceeds

the undervoltage lockout threshold level and the IC is

enabled via the MODE pin. If the battery has been deeply

discharged and the battery voltage is less than 2.7V, the

charger will begin with the programmed trickle charge

current.

Power Converter Operation from Battery

WhentheACadapterisremoved,theLTC1980operatesas

a DC/DC PWM converter using the battery for input power

to provide a regulated output voltage for the system load.

The LTC1980 is a current mode switcher. This means that

the switch duty cycle is directly controlled by switch

current rather than by output voltage or current. Battery

charger operation will be described for the simplified

diagram(Figure3). Atthestartoftheoscillatorcycle, latch

U9 is set causing M2 to turn on. When switch current

reaches a predetermined level M2 turns off and M1 turns

on. This level is set by the control voltage at the output of

error amplifier U10.

When the battery exceeds 2.7V, the charger begins the

constant-current portion of the charge cycle with the

charge current equal to the programmed level. As the

battery accepts charge, the voltage increases. When the

battery voltage reaches the recharge threshold, the pro-

grammable timer begins. Constant-current charging con-

tinuesuntilthebatteryapproachestheprogrammedcharge

voltage of 4.1V or 4.2V/cell at which time the charge

current will begin to drop, signaling the beginning of the

constant-voltage portion of the charge cycle. The charger

U1 VOLTAGE

SELECTION

V

BAT

REG

T1

WALL

ADAPTER

+

C2

B1

C1

SN1 SNUBBER

SN2 SNUBBER

R1

R2

NETWORK

–

+

U2

TO SYSTEM

LOAD

BDRIVE

RDRIVE

U4

DRIVERS

M1 M2

+

–

C6

R12

R13

DIRECTION

SENSE

V

REF

CURRENT

TYPICAL

U7

AMPLIFIER

WAVEFORM

OSC

R5

S

R

–

+

Q

U9

+

–

+

U6

–

U5

ZC

R4

U8

–

R6

PWM

C3

C4

SW1

R7

–

+

R9

SW3

R8

SW2

U10

R10

R11

–

EA

U12

+

C5

U11

REFERENCE

V

REF

1980 F03

Figure 3. Simplified Diagram—Power Converter

1980f

10

LTC1980

U

OPERATIO

TransformercurrentissensedacrossR_S,gainedupviaU6

and sampled through switch SW1. The current in R7 is a

scaled-downreplicaofthebatterychargingcurrentpulses

from the transformer. During battery charging, switch

SW2isinthedownpositionconnectingR7, R8, R9andC4

to the inverting input of amplifier U10 forming an integra-

tor which closes the outer loop of the converter and

establishes constant current charging. U12 is a g_mampli-

fierthatclampsU10asthebatteryfloatvoltageisreached.

R10andR11setthefloatvoltageandC5compensatesthis

loop and provides a soft-start function.

DC/DC Converter Operation

When the LTC1980 is operating as a DC/DC converter, M1

turns on at the start of the oscillator cycle. When trans-

former current reaches a predetermined level set by U10’s

outputvoltage,M1turnsoffandM2turnson.SW2isinthe

up position forming an integrator with zero, which com-

pares the output voltage (via R1 and R2 to reference U11

establishing the output voltage.

W U U

U

APPLICATIO S I FOR ATIO

Setting Battery Charge Current

where A_V= 2.44 and V_REF= 1.225V. The suggested value

for R7 is 10k.

Referring to the simplified schematic in Figure 4, the

averagecurrentthroughR7mustequalthecurrentthrough

R_TRKLwith switch SW3 open. This leads to the equation

for setting the trickle charge current:

Setting the Float Voltage

Pin selectable 4.1V, 4.2V, 8.2V, and 8.4V Li-Ion float

voltages are available. Other float voltages may be set via

external resistors. The following combinations of logic

inputs BATT1 and BATT2 determine the float voltage.

V_REF•R7

I_TRICKLE•R_S•A_V

R_TRKL

=

BATT2

BATT1

FLOAT VOLTAGE

Normal charge current is set via the parallel combination

of R_TRKLand R_CHRGwhich leads to the following equation

for R_CHRG

0

1

4.1V

0

4.2V

1

0

8.2V

8.4V

1

V_REF•R7

R_CHRG

=

Don’t Care

Open

Externally Set via OVP

I_NORMAL– I_TRICKLE•R_S•A_V

(

)

where logic 0 = GND and logic 1 = V

(Pin 19)

BIAS2

C4

V

REF

+

–

1.225V

I

V

C

SENSE

R7

21

+

U10

4

SW1

PROGT

10k

U6

= 2.44

I

R

22

CAOUT

2

S

A

–

V

20

GND

R

CHRG

TRKL

PROG

1

SW3

1980 F04

20

Figure 4. Battery Charger Current Control Loop

1980f

11

LTC1980

W U U

U

APPLICATIO S I FOR ATIO

An external resistor divider (Figure 3) can be used to

program other float voltages. Resistor values are found

using the following equation:

where V_IH1= 1.226V, suggested value for R7 is 100k. Use

1% resistors.

MODE Pin Operation

R10 = R11 • (V_FLOAT– V_REF)/V_REF

The following truth table describes MODE pin operation.

Burst Mode operation is disabled during battery charging

to reduce broadband noise inherent in Burst Mode opera-

tion. (Refer to the LT1307 data sheet for details).

where V_REF= 1.225V. The suggested value for R11 is

100k. Use 1% or better resistors.

Setting DC/DC Converter Output Voltage

POWER FLOW

Battery Charger

DC/DC converter

MODE PIN

OPERATING MODE

Disabled

From Figure 5, select the following resistors based on

0

output voltage V_REG

:

Open

Enabled Continuous

Disabled

R8 = R14 • (V_REG– V_REF)/V_REF

1

whereV_REF=1.225V,suggestedvalueforR14is100k, 1%.

0

Open

Enabled Burst Mode Operation

Enabled Continuous

LDO Operation

1

Logic 1 = V

(Pin 13) Logic 0 = GND

The LTC1980 provides an uninterrupted power supply for

the system load. When a wall adapter is connected and

operating, power is taken from the wall adapter to charge

the batteries and supply power to the system. In applica-

tions where an unregulated wall adapter is used but a

regulated voltage is needed by the system, an external P-

channel MOSFET pass transistor may be added to the

LTC1980 to create a low dropout linear regulator.

BIAS1

The MODE pin should be decoupled with 200pF to ground

when left open.

Snubber Design

The values given in the applications schematics have been

found to work quite well for most applications. Care

should be taken in selecting other values for your applica-

tionsinceefficiencymaybeimpactedbyapoorchoice.For

a detailed look at snubber design, Application Note 19 is

very helpful.

From Figure 5, select the following resistors based on the

output voltage V_LDO

:

R5 = R6 • (V_LDO– V_REF)/V_REF

whereV_REF=1.225V, suggestedvalueforR6is100k, 1%.

Frequency Compensation

This is the voltage that will be seen when operating from

a higher voltage wall adapter. When operating from the

batteries (as a regulator), the load will see either this

voltage or the voltage set by the PWM regulator, which-

ever is less, minus any drops in the pass transistor.

Load step testing can be used to empirically determine

compensation. Application Note 25 provides information

on the technique. To adjust the compensation for the DC/

DC converter, adjust C12 and R13 (in Figure 5). Battery

charger current loop compensation is set by C11 and

battery charger float voltage compensation is set by C8.

Placing a large-valued capacitor from the drain of this

MOSFET to ground creates output compensation.

Component Selection Basics

Wall Adapter Comparator Threshold

The application circuits work well for most 1- and 2-cell

Li-Ion, 0.5Ato1Aoutputcurrentdesigns. Thenextsection

highlights the component selection process. More infor-

mation is available in Application Note 19.

From Figure 5, select the following resistors based on the

wall adapter comparator threshold V_WATH

:

R15 = R7(V_WATH– V_IH1)/V_IH1

1980f

12

LTC1980

U

W

U U

APPLICATIO S I FOR ATIO

Current Sense Resistor

the transformer which can reduce the leakage inductance,

reducetheneedforaggressivesnubberdesignandforthis

reason improve efficiency.

Voltage drop in the current sense resistor should be

limited to approximately ±100mV with respect to ground

at max load currents in all modes. This value strikes a

reasonable balance between providing an adequate low

current signal, while keeping the losses from this resistor

low. Forapplicationswheretheinputsandoutputvoltages

may be low, a somewhat lower drop can be used (in order

to reduce conduction losses slightly).

Avoid transformer saturation under all operating condi-

tions and combinations (usually the biggest problems

occur at high output currents and extreme duty cycles.

Also check these conditions for battery charging and

regulation modes.

Finally, in low voltage applications, select a transformer

withlowwindingresistance.Thiswillimproveefficiencyat

heavier loads.

The LTC1980 has several features, such as leading-edge

blanking, whichmakeapplicationofthisparteasiertouse.

However for best charge current accuracy, the current

sense resistor should be Kelvin sensed.

Capacitors

Check the RMS current rating on your capacitors on both

sides of your circuit. Low ESR and ESL is recommended

for lowest ripple. OS-CON capacitors (from Sanyo) work

very well in this application.

MOSFETs

The LTC1980 uses low side MOSFET switches. There are

twoveryimportantadvantages.First,N-channelMOSFETs

are used—this generally means that efficiency will be

higher than a comparable on-resistance P-channel device

(because less gate charge is required). Second, low V_T

(‘logic-level’) MOSFETs with relatively low absolute maxi-

mum V_GSratings can be used, even in higher voltage

applications. Refer to Application Note 19 for information

on determining MOSFET voltage and current ratings.

Diodes

In low voltage applications, Schottky diodes should be

placedinparallelwiththedrainandsourceoftheMOSFETs

in the PWM supply. This prevents body diode turn on and

improves efficiency by eliminating loss from reverse re-

covery in these diodes. It also reduces conduction loss

during the RGTDR/BGTDR break interval.

Transformer

The LTC1980 can operate to voltages as low as 2.8V.

Suitable Schottky diodes include the ZHCS1000 (V_F=

420mV at I_F= 1A) and SL22/23 (V_F= 440mV at I_F= 2A) for

most 500mA to 1A output current applications.

Turns ratio affects the duty factor of the power converter

which impacts current and voltage stress on the power

MOSFETs, input and output capacitor RMS currents and

transformer utilization (size vs power). Using a 50% duty

factor under nominal operating conditions usually gives

reasonable results. For a 50% duty factor, the turns ratio

is:

Vendor List

VENDOR

COMPONENTS

Transformers

TELEPHONE

BH Electronics

952-894-9590

561-752-5000

Coiltronics/Cooper Electronic

Fairchild Semiconductor

N = V_REG/V_BAT

MOSFETs

Schottky Rectifiers

800-341-0392

NshouldbecalculatedforthedesignoperatingasaDC/DC

converter and as a battery charger. The final turns ratio

should be chosen so that it is approximately equal to the

average of the two calculated values for N. In addition

choose a turns ratio which can be made from the ratio of

small integers. This allows bifilar windings to be used in

Vishay (General Semiconductor) MOSFETs

Schottky Rectifiers

631-847-3000

Sanyo

OS-CON Capacitors 408-749-9714

Sumida Electric USA

Vishay (Siliconix)

Transformers

MOSFETs

847-956-0666

408-988-8000

1980f

13

LTC1980

U

TYPICAL APPLICATIO

D1*

IN5819

BH511-1014

V

3.3V

V

DC

OUT

REG

BAT

WALL

ADAPTER

AC

IN

4.1V

+

C1 5.1Ω

68µF

5.1Ω

C4

68µF

Li-Ion

BATTERY

OPTIONAL

PASS TRANSISTOR

FOR LDO FDC636P

1nF

V

3.1V

LDO

1/2 FDC6401N

SYSTEM LOAD

DC/DC

CONVERTERS

V

C6

470µF

OUT

50mΩ

SENSE

R5

154k

R

R6

100k

14

12

20

GND

21

11

RGTDR

7

6

5

8

WA

R15

300k

BGTDR PGND

I

V

LDODRV LDQFB

SENSE

REG

18

23

3

15

16

9

REG

MODE

BATT1

BATT2

V

OVP

REGFB

CAOUT

BAT

R7

100k

LTC1980

200pF

22

10

R8

169k

PROG

PROGT

2

V

TIMER

17

SS

24

V

C

4

BIAS1

13

BIAS2

19

1

R10

110k

C9

1µF

C7

0.27µF

C11

1nF

R9

10k

R12

100k

R14

100k

C8

0.1µF

C10

1µF

C12

82pF

*OPTIONAL DIODE FOR

SHORTED WALL ADAPTER

TERMINAL PROTECTION

R11

1M

R13

806k

1980 F05

Figure 5. 4.1V/1A Li-Ion Battery Charger and 3.3V DC/DC Converter

1980f

14

LTC1980

U

PACKAGE DESCRIPTIO

GN Package

24-Lead Plastic SSOP (Narrow .150 Inch)

(Reference LTC DWG # 05-08-1641)

.337 – .344*

(8.560 – 8.738)

.033

(0.838)

REF

24 23 22 21 20 19 18 17 16 15 14 13

.045 ±.005

.229 – .244

.150 – .157**

(5.817 – 6.198)

(3.810 – 3.988)

.254 MIN

.150 – .165

1

2

3

4

5

6

7

8

9 10 11 12

.0165 ±.0015

.0250 TYP

RECOMMENDED SOLDER PAD LAYOUT

.015 ± .004

(0.38 ± 0.10)

.053 – .068

(1.351 – 1.727)

× 45°

.004 – .0098

(0.102 – 0.249)

.007 – .0098

(0.178 – 0.249)

0° – 8° TYP

.016 – .050

(0.406 – 1.270)

.008 – .012

(0.203 – 0.305)

.0250

(0.635)

BSC

NOTE:

1. CONTROLLING DIMENSION: INCHES

INCHES

2. DIMENSIONS ARE IN

(MILLIMETERS)

GN24 (SSOP) 0502

3. DRAWING NOT TO SCALE

*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH

SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE

**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD

FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE

1980f

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 represen-

tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.

15

LTC1980

RELATED PARTS

PART NUMBER

DESCRIPTION

COMMENTS

LT1170/LT1171/LT1172 5A/3A/1.25A Flyback Regulators

Isolated Flyback Mode

LT1571

200kHz/500kHz Switching Battery Charger

Up to 1.5A Charge Current; Preset and Adjustable Battery Voltages

LTC1729

LTC1731

Lithium-Ion Battery Charger Termination Controllers Time or Charge Current Termination, Preconditioning 8-Lead MSOP

Lithium-Ion Linear Battery Charger Controller

Simple Charger uses External FET, Features Preset Voltages, C/10

Charger Detection and Programmable Timer

LTC1732

Lithium-Ion Linear Battery Charger Controller

Simple Charger uses External FET, Features Preset Voltages, C/10

Charger Detection and Programmable Timer, Input Power Good Indication

LTC1733

LTC1734

LTC1734L

LTC1760

LTC1960

Monolithic Lithium-Ion Linear Battery Charger

Lithium-Ion Linear Battery Charger in ThinSOT^TM

Lithium-Ion Linear Battery Charger Controller

Standalone Charger with Programmable Timer, Up to 1.5A Charge Current

Simple ThinSOT Charger, No Blocking Diode, No Sense Resistor Needed

50mA to 180mA, No Blocking Diode, No Sense Resistor Needed

Dual Battery Charger/Selector with SMBus Interface Complete SMBus Charger/Selector for Two Smart Batteries

Dual Battery Charger/Selector with SPI

Complete Dual-Battery Charger/Selector System, Easy Interface with

Microcontroller, Extends Run Time by 10%, reduces Charge Time by 50%

LTC4002

Wide V Range Li-Ion Battery Charger

1-, 2-Cell Batteries, Switch Mode Charger, Up to µA Charge Current,

IN

4.7V ≤ V ≤ 22V

IN

LTC4007

LTC4050

4A Standalone Multiple Cell Li-Ion Battery Charger

Lithium-Ion Linear Battery Charger Controller

6V ≤ V ≤ 28V, 3- or 4-Cell, Up to 96% Efficiency

IN

Simple Charger uses External FET, Thermistor Input for

Battery Temperature Sensing

LTC4052

LTC4411

LTC4412

Lithium-Ion Linear Battery Pulse Charger

2.6A Low Loss Ideal Diode in ThinSOT

Ideal Diode or PowerPath^TM

Fully Integrated, Standalone Pulse Charger, Minimal Heat Dissipation,

Overcurrent Protection

Very Low Loss Replacement for Power Supply ORing Diodes,

2.6V to 5.5V Supply Voltage, ThinSOTPackage

Very Low Loss Replacement for Power Supply ORing Diodes,

Enternal Pass Element, 3V to 28V Supply Voltage,ThinSOTPackage

ThinSOT and PowerPath are trademarks of Linear Technology Corporation.

1980f

LT/TP 0604 1K • PRINTED IN USA

LinearTechnology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

16

●

(408) 432-1900 FAX: (408) 434-0507 www.linear.com


型号：	LTC1980_1
厂家：	Linear
描述：	Combination Battery Charger and DC/DC Converter 组合电池充电器和DC / DC转换器转换器电池
文件：	总16页 (文件大小：235K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

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