Zetex ZXSC310E5 Datasheet

LED DRIVER SOLUTION FOR LCD BACKLIGHTING

DEVICE DESCRIPTION

ZXSC310

The ZXSC310 is a single or multi cell LED driver
designed for LCD backlighting applications. The input
voltage range of the device is between 0.8V and 8V.
This means the ZXSC310 is compatible with single
NiMH, NiCd or Alkaline cells, as well as multi-cell or
LiIon batteries.

The device features a shutdown control, resulting in a
standby current less than 5µA, and an output capable
of driving serial or parallel LED’s. The circuit generates
constant power output, which are ideal for driving
single ormultiple LED’s overa wide rangeof operating
voltages. These features make the device ideal for
driving LED’sparticularly in LCDbacklight applications
for Digital Still cameras and PDA’s.

FEATURES

· 94% efficiency

· Minimum operating input voltage 0.8V

· Maximum operating input voltage 8V

· Standby current less than 5µA

· Programmable output current

· Series or parallel LED configuration

· Low saturation voltage switching transistor

·

SOT23-5 package

APPLICATIONS

·

LCD backlights:

Digital still camera
PDA
Mobile phone

·

LED flashlights and torches

·

White LED driving

·

Multiple LED driving

The ZXSC310 is a PFM DC-DC 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 conversion
enabling high efficiency conversion with low input
voltages. The drive output of the ZXSC310 LED driver
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 optimumefficiency over a wider
range of load currents; several circuit configurations
are possible depending on battery life versus
brightness considerations.

The ZXSC310is offered in the SOT23-5package 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 LED backlight
applications.

TYPICAL APPLICATIONS CIRCUIT

V

= 3.3V / 5V

IN

V

CC

V

DRIVE

S

TDN

I

SENSE

Gnd

ORDERING INFORMATION

DEVICE REEL

SIZE

ZXSC310E5 180mm 8mm 3000

TAPE

WIDTH

QUANTITY

PER REEL

DEVICE MARKINGS

·

C310

PROVISIONAL ISSUE A - SEPTEMBER 2001

1

ZXSC310

ABSOLUTE MAXIMUM RATINGS:

Supply Voltage -0.3 to 10V
Maximum Voltage other pins -0.3 to V
Power Dissipation 450mW
Operating Temperature -40 to 85 °C
Storage Temperature -55 to 125°C

ELECTRICAL CHARACTERISTICS:

Test conditions unless otherwise stated: VCC=1.5V, T

Symbol Parameter Conditions Min Typ Max Units

␩ Efficiency
V

CC

V

CC(min)

I

Q

I

VDRIVE

I

CC

Recommended supply
voltage range

Minimum startup and
operating voltage

Quiescent current

Base drive current V
Supply current

1

I

=-600µA,V

DRIVE

=-600µA, V

I

DRIVE

T

=-10°C3

2

3

AMB

V

EN =VCC

0V (standby)

V

EN =

DRIVE

V

DRIVE

(enabled)

= 0.7V, V

= 0.7V, V

+0.3V

CC

=25 C

AMB

0.8 8 V

DRIVE

DRIVE

=0.7V

=0.7V,

0.8

0.9

0.2
45mAµA

= 0V 1.5 3.5 mA

ISENSE

=0V 2 4 mA

ISENSE

94 %

0.92 V

V

VDRIVE(high)

V

VDRIVE(low)

V

EN(high)

V

EN(low)

I

EN

V

ISENSE

(threshold)

T

CVISENSE

I

ISENSE

ELECTRICAL CHARACTERISTICS: AC PARAMETERS
Test conditions unless otherwise stated: VCC=1.5V, T

Symbol

T

DRV

F

OSC

1 Application dependent, see reference designs
2 These parameters guaranteed by Design
3 Total supply current =I
4 Operating frequency is application circuit dependent. See applications section.

High level drive voltage V

Low level drive voltage V

ISENSE

ISENSE

=0V,I

VDRIVE

= 50mV, I

=-0.5mA V

= 5mA 0 0.2 V

VDRIVE

Device enabled 0.7 V
Device in standby mode 0.15 V
Enable input current -1 1 µA
Output current reference

voltage

I

voltage temp co.

SENSE

I

input current V

SENSE

2

= 0V 0 -30 -65 µA

ISENSE

2

=0 to 70 C

AMB

Parameter Conditions Min Typ Max Units

Discharge Pulse Width 1.2 1.7 3.2 µs

Recommended operating

frequency

+ I

Q

4

, see typical characteristics

VDRIVE

PROVISIONAL ISSUE A - SEPTEMBER 2001

CC

V

CC

-0.3

14 19 24 mV

0.4 %/°C

200 kHz

V

2

ZXSC310

FMMT618

For the circuits described in the applications section
Zetex FMMT618 is the recommended pass transistor.

ELECTRICAL CHARACTERISTICS:
Test conditions unless otherwise stated: T

Symbol Parameter Conditions Min Typ Max Units

V

CE(sat)

V

(BR)CEO

5

Measured under pulse conditions. Pulse width=300µs. Duty cycle ⱕ2%

Collector-Emitter
Saturation Voltage

Collector-Emitter
Breakdown Voltage

5

5

IC=0.1A, IB=10mA
I

C

I

C

IC=10mA 20 27 V

ZHCS1000

The following indicates outline data for the device,
more detailed information can be found in the Zetex
surface mount products data book or on Zetex Web
page: www.zetex.com

=25 C

AMB

8
=1A, IB=10mA
=2.5A, IB=50mA

70

130

15
150
200

mV

For the maximum brightness circuit described in the
applications section Zetex ZHCS1000 is the
recommended Schottky diode.

The following indicates outline data for the ZHCS,
more detailed information can be found on Zetex Web
page: www.zetex.com

ELECTRICAL CHARACTERISTICS:
Test conditions unless otherwise stated: T

Symbol Parameter Conditions Min Typ Max Units

V

F

t

rr

I

R

Part

Number

BAT54 30 200 0.6 500 30 250 25 10 SOT23-6
ZHCS2000 40 2000 20 500 2000 1000 30 60 SOT23
ZHCS1000 40 1000 12 500 1000 100 30 25 SOT23

ZHCS750 40 750 12 540 750 100 30 25 SOT23
ZHCS500 40 500 6.75 550 500 40 30 20 SOT23
ZHCS400 40 400 6.75 500 400 40 30 20 SOT323

Forward voltage IF= 500mA

I

F

Reverse Recovery Time Switched from IF=500mA to

I

R

Measured at I

Reverse Current VR= 30V 50 100 µA

V

I

R

I

F

FSM

VFat IRat Capacitance

Max.VMax.mAMax.AMax.mVI

mA

AMB

=1A

=500mA.

Max.␮AV

F

=25 C

=50mA

R

R

V

= 25V, f = 1MHz

at V

R

Typ.

pF

400
500

12 ns

Package

SOT23

mV

PROVISIONAL ISSUE A - SEPTEMBER 2001

3

ZXSC310

TYPICAL CHARACTERISTICS

PROVISIONAL ISSUE A - SEPTEMBER 2001

4

DEVICE DESCRIPTION

ZXSC310

The ZXSC310 is PFM, controller IC which, when
combined witha high performance external transistor,
enables the production of a high efficiency boost
converter for LED driving applications. A block
diagram is shown for the ZXSC310 below.

The on chip comparator forces the driver circuit and
therefore the external switching transistor off if the
voltage at I
circuit and divider set this threshold.

The voltage at I
resistor connected in series with the emitter of the
switching transistor. A monostable following the
output ofthe comparator forcesthe turn-off timeof the
output stage to be typically 1.7us. This ensures that
there is sufficient time to discharge the inductor coil
before the next on period.

exceeds 19mV. An internal reference

SENSE

is taken from a current sense

SENSE

V

CC

I
2

With every on pulse the switching transistor is kept on
until the voltage across the current-sense resistor
exceeds thethreshold ofthe I
length, and therefore the switching frequency, is
determined by the programmed peakcurrent,theinput
voltage and the inputtooutputvoltagedifferential. See
applications section for details.

The driver circuit supplies the external switching
transistor with a fixed drive current. To maximise
efficiency the external transistor switched quickly,
typically being forced off within 30ns.

Drive

input. Theon-pulse

SENSE

S

TDN

R1

V

RE

R2

G

N

D

ZXSC310 Block Diagram

PROVISIONAL ISSUE A - SEPTEMBER 2001

I

5

V

DRIVE

I

SENSE