Zetex (Now Diodes) ZXSC300 Schematic [ru]

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ZXSC300

SINGLE OR MULTI CELL LED DRIVER SOLUTION

DESCRIPTION

The ZXSC300 is a single or multi cell LED driver designed for applications where step-up voltage conversion from very low input voltages is required. These applications mainly operate from single 1.5V or

1.2V battery cells. The circuit generates constant current pulses that are ideal for driving single or multiple LED’s over a wide range of operating voltages.

The ZXSC300 is a PFM controller IC that drives an external Zetex switching transistor with a very low saturation resistance. These transistors are the best switching devices available for this type of switching conversion enabling high efficiency conversion with input voltages below 1 volt. The drive output of the ZXSC controller generates a dynamic drive signal for the switching transistor.

The circuit can start up under full load and operates down to an input voltage of 0.8 volts. The solution configuration ensures optimum efficiency over a wide range of load currents, several circuit configurations are possible depending on battery life versus brightness considerations.

The ZXSC300 is offered in the SOT23-5 package which, when combined with a SOT23 switching transistor, generates a high efficiency small size circuit solution. The IC and discrete combination offers the ultimate cost vs performance solution for single cell LED driving applications.

FEATURES

APPLICATIONS

94% efficiency

LED flashlights and torches

Minimum operating input voltage 0.8V

LED backlights

Fixed output current

White LED driving

Low saturation voltage switching transistor

Multiple LED driving

SOT23-5 package

Solar Equipment

TYPICAL APPLICATION CIRCUIT

ORDERING INFORMATION

 

 

L1

 

DEVICE

Reel

Tapewidth

Quantity

VBATT

 

 

 

 

per reel

 

100µH

 

ZXSC300E5TA

7”

8mm

3,000

 

U1

Q1

 

 

 

 

 

Vcc

FMMT617

DEVICE MARKING C300

 

 

LED1

 

 

Vdrive

Package SOT23-5

 

 

 

 

WHITE LED

 

 

 

 

Isense

 

 

 

 

 

 

Gnd

 

 

 

 

 

 

ZXSC300

R1

 

 

 

 

 

 

0.33R

 

 

 

 

ISSUE 3 - NOVEMBER 2006

1

ZXSC300

ABSOLUTE MAXIMUM RATING

Supply Voltage

-0.3 to 10V

Operating Temperature

-40 to 85°C

Maximum Voltage Other Pins -0.3 to VCC+0.3V

Storage Temperature

-55 to 150°C

Power Dissipation

450mW

 

 

ELECTRICAL CHARACTERISTICS: Test conditions unless otherwise stated: VCC=1.5V, TAMB=25°C

SYMBOL

PARAMETER

CONDITIONS

MIN.

TYP.

MAX.

UNITS

 

 

 

 

 

 

 

η

Efficiency1

 

 

 

94

%

VCC

Recommended

 

0.8

 

8

V

 

supply voltage range

 

 

 

 

 

 

 

 

 

 

 

 

VCC(min)

Minimum startup

IDRIVE=-600µA, VDRIVE=0.7V

 

0.8

0.92

V

 

and operating

IDRIVE=-600µA, VDRIVE=0.7V,

 

0.9

 

 

 

voltage

 

 

 

 

TAMB=-10°C3

 

 

 

 

IQ

Quiescent current2

 

 

0.2

 

mA

IVDRIVE

Base drive current

VDRIVE = 0.7V, VISENSE = 0V

1.5

 

3.6

mA

ICC

Supply current3

VDRIVE = 0.7V, VISENSE = 0V

2

 

4

mA

VVDRIVE(high)

High level drive

VISENSE = 0V, IVDRIVE =-0.5mA

VCC-0.3

 

VCC

V

 

voltage

 

 

 

 

 

 

 

 

 

 

 

 

VVDRIVE(low)

Low level drive

VISENSE = 50mV, IVDRIVE = 5mA

0

 

0.2

V

 

voltage

 

 

 

 

 

 

 

 

 

 

 

 

VISENSE

Output current

 

14

19

24

mV

(threshold)

reference voltage

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

TCVISENSE

ISENSE

 

 

0.4

 

%/°C

 

voltage temp co.2

 

 

 

 

 

IISENSE

ISENSE input current

VISENSE = 0V

0

-30

-65

µA

TDRV

Discharge pulse width

 

1.2

1.7

3.2

µs

OPERATING CONDITIONS

SYMBOL

PARAMETER

CONDITIONS

MIN.

TYP.

MAX.

UNITS

 

 

 

 

 

 

 

FOSC

Recommended operating frequency4

 

 

 

200

kHz

 

 

 

 

 

 

 

1Application dependent, see reference designs.

2These parameters guaranteed by design and characterisation

3Total supply current =IQ + IVDRIVE, see typical characteristics

4Operating frequency is application circuit dependent. See applications section.

ISSUE 3 - NOVEMBER 2006

2

ZXSC300

FMMT617

For the circuits described in the applications section, Zetex FMMT617 is the recommended pass transistor. The following indicates outline data for the transistor, more detailed information can be found in the Zetex surface mount data book or at www.zetex.com

ELECTRICAL CHARACTERISTICS (at TA = 25°C unless otherwise stated).

PARAMETER

SYMBOL

MIN.

TYP.

MAX.

UNIT

CONDITIONS

 

 

 

 

 

 

 

Collector-Emitter

VCE(sat)

 

8

14

mV

IC=0.1A, IB=10mA*

Saturation Voltage

 

 

70

100

mV

IC=1A, IB=10mA*

 

 

 

150

200

mV

IC=3A, IB=40mA*

Collector-Emitter

V(BR)CEO

15

18

 

V

IC=10mA*

Breakdown Voltage

 

 

 

 

 

 

 

 

 

 

 

 

 

*Measured under pulsed conditions. Pulse width=300 s. Duty cycle 2%

ZHCS1000

For the circuits described in the applications section Zetex ZHCS1000 is the recommended Schottky diode. The following indicates outline data for the diode, more detailed information is available at www.zetex.com

ELECTRICAL CHARACTERISTICS (at Tamb = 25°C unless otherwise stated).

PARAMETER

SYMBOL

MIN.

TYP.

MAX.

UNIT

CONDITIONS

 

 

 

 

 

 

 

Forward Voltage

VF

 

 

400

mV

IF=500mA

 

 

 

 

500

mV

IF=1A

Reverse Current

IR

 

50

100

A

VR=30V

 

 

 

 

 

 

 

Reverse Recovery

trr

 

12

 

ns

Switched from IF = 500mA

Time

 

 

 

 

 

to IR = 500mA. Measured

 

 

 

 

 

 

at IR=50mA

*Measured under pulsed conditions. Pulse width=300 s. Duty cycle 2%

ISSUE 3 - NOVEMBER 2006

3

ZXSC300

TYPICAL CHARACTERISTICS

ISSUE 3 - NOVEMBER 2006

4

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