TOKO TK11850LTL Datasheet

TK11850L

I

S

EXT

V

IN

V

OUT

GND

7

C

X

8

EN

V

FB

+

-

+

-

BAND GAP REFERENCE

OSC

C

X

CLK

0.86 V

0.3 V

CLK

S

R

Q

V

REF

0.525 V

ERROR

COMP

IS COMP

0.1 V

WHITE LED DRIVER

FEATURES

n Very High Speed Adjustable OSC (Max 800 kHz) n Very Wide Operating Voltage Range (2.3 V to 10 V) n Low Loss Detector (Low Reference Voltage:

V

= 0.5 V)

REF

n Operates with Toko D31FU Miniature Coil (Current

Limited by Input Current Sensor)

n Internal Switching Transistor n Internal Diode n Active High On / Off Control n Available Intensity Control Using EN Pin with PWM

Signal

n Very Small SOT23L-8 Surface Mount Package

DESCRIPTION

The TK11850L is a pulse skipping step-up DC-DC converter IC designed for White LED driver applications with the following built in: a very high current switching transistor (400 mA peak), an inductor current limit detector, low voltage reference (Vref = 0.5 V), high speed oscillator, an error comparator, a rectifier diode (for small power output) and an ON/OFF control. The IC works with a very wide operating supply range (2.3 V to 10 V) and the adjustable output voltage can be set as high as 20 V. The device is in the ON state when the EN pin is pulled to a high level. Using the very small TK11850L and a few external components, battery powered systems with LCD displays such as digital cameras and cellular phones can be effectively backlit with white LEDs. The white LEDs are connected in series and driven at a constant current resulting in uniform brightness and high efficiency. This IC has an oscillator, which allows the designer to set the operating frequency by an external capacitor with the output controlled by pulse skipping. The reference voltage is a very low 0.5 V, achieving high efficiency operation with the constant current output. A small coil can be used because the inductor current limit detector circuit limits the peak current (caused by an input

APPLICATIONS

n LED Backlighting and Frontlighting n LED Flashlights n Step-up DC-DC Converters

voltage increase or the inrush current as start-up) that flows through the coil. The ON /OFF control is built-in and the circuit current can be decreased when the EN pin is low (standby mode). The white LEDs can be dimmed by applying a PWM signal to the EN (ON/OFF control) pin. With this method, the white LED brightness is still controlled by constant current resulting in constant chromaticity.

The TK11850L is available in the SOT23L-8 surface mount package.

TK11850

V

IN

I

S

EXT

V

OUT

BLOCK DIAGRAM

8EN

C

7

X

GND

V

FB

ORDERING INFORMATION

May 2001 TOKO, Inc. Page 1

TK11850L

Tape/Reel Code

TAPE/REEL CODE

TL: Tape Left

TK11850L

ABSOLUTE MAXIMUM RATINGS

Supply Voltage........................................................ 20 V

Switching Voltage .................................................... 20 V

Operating Voltage Range ............................... 2.3 to 10 V

Power Dissipation (Note 1) ................................. 400 mW

Storage Temperature Range .....................-55 to +150 °C

TK11850 ELECTRICAL CHARACTERISTICS

Test Conditions: VIN = 3 V, V

LOBMYSRETEMARAPSNOITIDNOCTSETNIMPYTXAMSTINU

=VEN = VIN, V

IS

)NIP

C(NOITCESROTALLICSO

X

= Open, VFB = GND, CX = 100 pF, TA = 25 °C, unless otherwise specified.

EXT

Operating Temperature Range.....................-30 to +85 °C

Switching Peak Current....................................... 400 mA

Diode Current ........................................................ 10 mA

Maximum Frequency ...................................... ~ 800 kHz

I

GHC

I

SID

I/

I

SID

V V V

CSO

V

TIMIL

I

nIsI

C

X

C

X

GHC

C

)HGIH(XC

X

C

)WOL(XC

X

C

X

oitaRtnerruC

egatloV

I

S

tnerruCgnigrahCV

tnerruCgnigrahcsiDV

XC

egrahcsiDdnaegrahC

+egatloVdlohserhTV

-egatloVdlohserhTV

XC

V1.0=612203 V0.1=539456

2.2

Ita

0= mA018068019Vm

GHC

Ita

0= mA062003043Vm

SID

egatloVnoitallicsO)-htV(-)+htV(025065006Vm

)NIP

I(NOITCESROTARAPMOCGNITIMILTNERRUC

S

esneStimiLtnerruC

V

tnerruCsaiBniPV

V=

TIMIL

V=

NI

V-

NI

SI

V3=50151

SI

277728Vm

mA mA

mA

)NIPTXE(NOITCESHCTIWSTUPTUO

V

taS,WS

I

ffO,WS

rotsisnarTtuptuO

egatloVnoitarutaS

ffOrotsisnarTtuptuO

tnerruCegakaeL

V

XC

V

BF

I,V0=

WS

V,V1=

TXE

Am002=2.04.0V

V02=10.02

mA

V(NOITCESROTARAPMOCKCABDEEF

V

FER

I

nIBF

Note 1: Power dissipation is 400 mW when mounted. Derate at 3.2 mW / °C for operation above 25 °C.

V

BF

egatloVecnerefeR505.0525.0545.0V

tnerruCtuptuOniPV

)NIP

BF

V4.0=2-3.0-

Page 2 May 2001 TOKO, Inc.

mA

TK11850 ELECTRICAL CHARACTERISTICS (CONT)

Test Conditions: VIN = 3 V, VIS =VEN = VIN, V

LOBMYSRETEMARAPSNOITIDNOCTSETNIMPYTXAMSTINU

)NIPNE(NOITCESNWODTUHS

= Open, VFB = GND, CX = 100 pF, TA = 25 °C, unless otherwise specified.

EXT

TK11850L

V V

I

V

V I I

)HGIH(NE

)WOL(NE

nINE

F

NI

)WOL(NI

)HGIH(NI

)ffO(CC

)nO(CC

V(NOITCES

NI

egatloVdrawroFI

)NIP

+egatloVdlohserhTNEedoMnO2V

-egatloVdlohserhTNEedoMnwodtuhS6.0V

tnerruCsaiBniPNEV

V-NIPTXE(NOITCESEDOID

)NIP

TUO

V=

NI

D

V3=258

NE

Am01=57.0V

mA

potSegatloVwoL7.10.23.2V

potStuptuOegatloVhgiH115.2141V

tnerruCylppuSnwodtuhSV

tnerruCylppuStnecseiuQV

v0=10.01

NE

V1=15.12Am

BF

mA

eulaVecnerefeR

I

η

ycneiciffE

DAOL

V

NI

V,Am02=

TUO

)2etoN(V6.3=

,V5.61=

87%

Note 2: This value is different depending on the components used, circuit conditions, etc. Thus, this is reference data only. Refer to Reference data test circuit.

May 2001 TOKO, Inc. Page 3

TK11850L

TEST CIRCUIT

I

CC

V

IN

V

IN

I

IS

I

EXT

I

VOUT

IN

V

IS

V

EXT

V

OUT

V

V V

10 µF

I

S

EXT

V

OUT

EN

C

GND

V

FB

X

8

7

100 pF

V

EN

V

CX

V

FB

I

EN

I

DIS

I

CHG

I

FB

REFERENCE DATA TEST CIRCUIT

I

C 47µ

LOAD

20 mA

OUT

I

CC

3.6 V

R

SC

0.22Ω

V

IN

V

C 47µ

IN

V

8

EN

IN

C

X

56 pF

I

TK11850L

C

L

15µ

V

S

OUT

7

GND

X

EXT

V

FB

D

620k

20k

V

2200p

L = 15 mH D52LC (A914BYW - 150M) Toko D - SB07 - 03C Sanyo

OUT

Page 4 May 2001 TOKO, Inc.

TYPICAL PERFORMANCE CHARACTERISTICS

SUPPLY CURRENT (mA)

10

SUPPLY CURRENT vs.

EN VOLTAGE

EN VOLTAGE (V)

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

9

8 7 6 5 4

3

2 1 0

-20 °C 25 °C

85 °C

VIN = 3 V

VIS = V

IN

VFB = 0 V

CX = 100 pF

TA = 25 °C, unless otherwise specified.

TK11850L

OSC PERIOD vs. C

CAPACITANCE

12

11

10

9

VIN = 3 V VIS = VEN = V

IN

8

7 6 5 4

OSC PERIOD (µS)

3 2 1 0

0 100 200 300

CX CAPACITANCE (pF)

SWITCHING CURRENT vs.

SWITCH SATURATION VOLTAGE

500

400

300

200

100

VIN = 3 V VIS = VEN = V VFB = 0 V VCX = 0 V

IN

SWITCHING CURRENT (mA)

0

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

SWITCH SATURATION

VOLTAGE (V)

X

-20 °C 25 °C

85 °C

OSC FREQUENCY vs.

TEMPERATURE

300 280

VIN = 3 V V VIN = 10 V

260

240

220

VIS = VEN =V CX = 100 pF

200

OSC FREQUENCY (kHz)

180

-30 -10 10 30 50 70 90

IN

TEMPERATURE (°C)

INDUCTOR CURRENT-LIMIT SENSE

VOLTAGE vs. SUPPLY VOLTAGE

100

90 80 70 60

50 40 30 20

SENSE VOLTAGE (mV)

INDUCTOR CURRENT-LIMIT

10

0

2 4 6 8 10 12

SUPPLY VOLTAGE (V)

IN = 5 V

V

limit

VEN = V

-20 °C 25 °C

85 °C

= VIS - V

IN

MAXIMUM DUTY CYCLE vs.

OSC FREQUENCY

80

VIN = 3 V VIS = V

EN = VIN

VFB = 0 V

75

70

MAXIMUM DUTY CYCLE (%)

65

10 100 1000

OSC FREQUENCY (kHz)

IS INPUT BIAS CURRENT

vs. IS VOLTAGE

100

90

80

-20 °C 25 °C

85 °C

70

IN

60 50 40 30 20

INPUT BIAS CURRENT (µA)

10

S

I

0

0 2 4 6 8 10 12 14 16 18 20

VIN = VEN = V VFB = 1 V

IS

IS VOLTAGE (V)

REFERENCE VOLTAGE vs.

SUPPLY VOLTAGE

530

528

526 524 522 520 518

REFERENCE VOLTAGE (mV)

516

0 2 4 6 8 10

SUPPLY VOLTAGE (V)

May 2001 TOKO, Inc. Page 5

VIS = VEN = V

REFERENCE VOLTAGE vs.

TEMPERATURE

530

528

VIN = 3 V VIS = VEN = V

IN

526

IN

524 522

520 518

REFERENCE VOLTAGE (mV)

516

-30 -10 10 30 50 70 90 TEMPERATURE (°C)

TOKO TK11850LTL Datasheet

Specifications and Main Features

Frequently Asked Questions

User Manual