Diodes ZXLD1322 User Manual

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ZXLD1322

BUCK/BOOST MODE DC-DC CONVERTER FOR LED DRIVING WITH 700mA OUTPUT AND CURRENT

CONTROL

Description

The ZXLD1322 is an inductive DC-DC converter, with an internal switch, designed for driving single or multiple LEDs in
series up to a total of 700mA output current. Applications cover input v oltages ranging from 2.5V to 15V. Depe nding upon
supply voltage and external components, this can provide up to 12W of output power. The device em ploys a variable 'on'
and 'off' time control scheme with adjustable peak switch current limiting and operates i n Buck/Boost mode, offering higher
power efficiency and lower system cost than conventional PFM buck/boost circuitry. The device includes the DC-DC
converter, a high-side current monitor and an NPN switching transistor to provide an integrated solution offering small PCB
size, competitive cost/performance, high power efficiency of DC-DC conversion and maximum L ED brightness/reliability.
More importantly, it retains design flexibility to add customer specific features. T he feedback control circuitry inside the
ZXLD1322 provides excellent load and current regul ation, resulting in very stable LED current over the useful life of the
battery and over the full operating temperature range. The LED curre nt can b e adjusted from 100 % down to 10% of t he set
value by applying a dc voltage to the ADJ pin and do wn to 1% b y appl ying a PWM sign al. An on-c hip LE D protecti on cir cuit
also allows output current to be reduced linearly above a predet erm ine d thresho ld temper ature using a n ext ernal thermi stor
at the TADJ pin. External resistors set nominal average LE D current a nd coil pe ak current indep endently. The dev ice can
be shut down by applying a continuous low level dc voltage to the ADJ pin.

Features

• 2.5V to 15V Input Voltage Range

• Up to 700mA output current

• Typical efficiency

• User-defined thermal control of LED

• output current using external thermistor

• High output current stability over input

• voltage and temperature

• 12A typical standby current

• LED current adjustable from 100%

• down to 2%

• Adjustable Soft-Start

• Capable of driving 3 LEDs in series

#

>80%

Applications

• High power LED flashlights

• LED back-up lighting

• General LED lighting

Typical Application Circuit

Pin Assignments

DFN4030-14 with Exposed Pad

0.50mm pitch

1.5W @ T

DFN4030-14 Package(Bottom View)

45° chamfer denote Pin 1

(Top View)

4mm x 3mm

= 70°C

A

Notes: #. Using standard external components as specified under electrical characteristics. Efficiency is dependent upon external component types and
values. Higher efficiency is possible with alternative coils.

ZXLD1322

Document number: DS32166 Rev. 3 - 2

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ZXLD1322

Block Diagram

ZXLD1322

Document number: DS32166 Rev. 3 - 2

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ZXLD1322

Pin Description

Name Pin # Description

Adjust input

• Leave floating, or connect to V

• Drive with dc voltage. (50mV<V

ADJ 1

of set value. (DC brightness control mode)

• Drive with low frequency (200Hz) PWM control signal to gate output ‘on’ and ‘off’ at
the PWM frequency. (PWM brightness control mode)

• Drive with low level dc voltage (V

Bias pin for setting base current of internal switch transistor

• Short pin to ground to define maximum base drive current for output switch

BIAS 2

(Maximum output current condition)

• Connect resistor (R

) from this pin to ground to reduce base drive current

BIAS

(Reduced output current condition)

CFB 3

Control input/output for feedback control loop

• Connect 10nF capacitor from this pin to ground to provide loop compensation

N/C 4 Not connected internally (Open circuit)

Switch peak current sense pin

ISENSE 5

EMITTER1 6

EMITTER2 7
COLLECTOR2 8
COLLECTOR1 9

• Connect resistor (R

SWPEAK

)=0.05/RS

(I

Switch emitters (Connect both pins to top of RSENSE to sense emitter current)
Switch Collectors (Connect both pins to lower side of coil)

) from this pin to ground to define peak switch current

SENSE

N/C 10 Internally connected - Do not connect to external circuitry

Input supply to high side current monitor

M_VIN 11

VIN 12

• Connect output voltage (whichever is higher)

• Connect resistor (R
current of 0.1/R

) from this pin to to VIN to define nominal average output (LED)

M

M

Input supply voltage and load side input of high side current monitor.
Connect to sensing resistor RM.
Temperature Adjust input for LED thermal compensation

• Connect thermistor/resistor network to this pin to reduce output current above a

TADJ 13

preset temperature threshold.

• Connect to V

to disable thermal compensation function

REF

(see section on temperature control for details)

VREF 14 Internal 0.5V reference voltage output

Exposed Pad 15 Connect to ground (0V)

ZXLD1322

Document number: DS32166 Rev. 3 - 2

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to set 100% output current.

REF

< V

ADJ

ADJ

) to adjust output current from 10% to 100%

REF

<28mV) to turn off device (Standby mode)

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ZXLD1322

Absolute Maximum Ratings (Voltages to GND Unless Otherwise Stated)

Symbol Parameter Rating Units

TOP
TST

TJ

P

TOT

DC-DC Converter

Supply Voltage (VIN) -0.3V to +15V

High-Side Current Monitor

Monitor Supply Voltage (M_VIN) -0.3V to +15V
Continuous Sense Voltage
(M_V

Switching NPN Transistor

Symbol Parameter Rating Units

V

CBO

V

CEO

ICM

IC

These are stress ratings only. Operation outside the absolute maximum ratings may cause device failure. Operation at the absolute maximum ratings for
extended periods may reduce device reliability.

Thermal Resistance

Junction to ambient (R

DFN4030-14 26.3°C/W

ZXLD1322

Document number: DS32166 Rev. 3 - 2

Operating Temperature -40 to 125 °C
Storage Temperature -55 to 150 °C
Junction Temperature -40 to 150 °C

Package Power Dissipation

DFN14 with Exposed Pad: 4mm x 3mm, 0.5mm Pitch

ADJ
CFB

I

-0.3V to The lower of (+5.0V) or (VIN + 0.3V)

SENSE

T

-0.3V to The lower of (+5.0V) or (VIN + 0.3V)

ADJ

BIAS

– M_LOAD)

IN

Collector-Base Voltage 18 V
Collector-Emitter Voltage 18 V

Peak Pulse Current

Continuous Collector Current

-0.3V to The lower of (+5.0V) or (V

-0.3V to The lower of (+5.0V) or (V

-0.3V to The lower of (+5.0V) or (V

-0.3V to +5V

Nominal Value

)

θJC

(Pulsed Width = 300µs. Duty Cycle<=2%)

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+ 0.3V)

IN

+ 0.3V)

IN

+ 0.3V)

IN

1.5 at T

=70°C

AMB

3

2 A

W

A

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ZXLD1322

Electrical Characteristics (Test conditions: V

= 4V, T

IN

= 25°C unless otherwise stated

AMB

DC-DC Converter Supply Parameters

Symbol Parameter Condition Min. Typ. Max. Unit

VIN
V

IN(Start)

VUV-

VUV+

Iq Quiescent Current
I

STBY

V

REF

T

CO(REF)

Notes: (a) Production testing of the device is performed at 25°C. Functional operation of the device and parameters specified from -40°C to +125°C are

guaranteed by design, characterization and process control.

(b) Between 1.2V and 2.2V the device will run in the Low Voltage Startup Mode (for details refer to section "Low Voltage Operation")

Supply Voltage Normal Operation 2.5 15 V
Supply voltage for start-up(b) Start-up mode 1.2 2.4 V

Under-voltage detection threshold
normal operation to start-up mode

Under-voltage detection threshold
start-up mode to normal operation

VIN falling 1.8 V

VIN rising 2.2 V
Measured into V

ADJ pin floating.

IN

Excluding switch base current).

Standby Current
Internal Reference Voltage

Internal Reference Temperature
Coefficient

Measured into VIN. ADJ pin grounded
ADJ pin floating

2.5V<V

<15V

IN

DC-DC Converter Input Parameters

Symbol Parameter Condition Min. Typ. Max. Unit

V

SENSE

V

SENSE

(SU)

I

SENSE

CFB
V

ADJ

V

ADJ(th)

T

CO

(V

)

ADJ

R

ADJ

V

ADJ

(CLMP)

Peak switch current sense voltage
Peak switch current sense voltage in

start-up mode
Sense input current

Control loop compensation capacitor 10
External DC control voltage applied to

ADJ pin to adjust output current
Switching threshold of ADJ pin Standby state to normal operation 26 28 30 mV

Temperature coefficient of V
Internal resistor between V

ADJ
Clamp voltage on ADJ pin 100A injected into ADJ pin 575 mV

ADJ(th)

REF

and

Measured on I

SENSE

pin CFB pin

at 0V
Measured on I

SENSE

pin. Start-up

mode VIN = 1.2V
Measured into I

SENSE

with pin at

0V. CFB pin at 0V

DC brightness control mode 50 500 mV

+0.3 %/K

V

<550mV

ADJ

DC-DC Converter Output Parameters

Symbol Parameter Condition Min. Typ. Max. Unit

Toff(100) Discharge pulse width 100% Output current 0.7 1.2 1.7 µs
Toff(10) Discharge pulse width 10% Output current 4 8 12 µs

f

LXMAX

fSU

Maximum operating frequency 600 KHz
Switching frequency in start-up mode VIN = 1.2V 50 KHz

ZXLD1322

Document number: DS32166 Rev. 3 - 2

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(a)

)

1.5 mA
12 20 µA

480 500 520 mV

50 ppm/K

45 55 65 mV

10.5 mV

-15 -7 -1 µA

100 k

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ZXLD1322

Switching NPN Transistor

Symbol Parameter Condition Min. Typ. Max. Unit

ISW
I

BON(max)

Average continuous switch current
Maximum base current into switch

transistor from internal drive circuit
Base current into switch transistor

I

BON

using external resistor (R

BASE

BIAS pin to ground

V

(BR)CE

V

CE(sat)

hFE
C

OBO

Collector-Emitter breakdown voltage
Collector-Emitter saturation voltage

Static forward current transfer ratio

Output capacitance
t(on) Turn-on time
t(off) Turn-off time

High-Side Current Monitor

Symbol Parameter Condition Min. Typ. Max. Unit

V

M_VIN

V

MON

I_

M_VIN

TCO

(MON)

Supply voltage 2.5 18 V
Sense voltage
Input current Measured into M_VIN pin 0.08 1 µA

Temperature coefficient

BW Bandwidth

Gm

ACC

Tran conductance

/VMON

I

OUT

Accuracy

Reference Current Monitor

Symbol Parameter Condition Min. Typ. Max. Unit

V

ADJ

TCO

(MON)

Adjust Voltage 0 500 mV

Temperature coefficient

BW Bandwidth

Gm
ACC

Notes: (c) Measured under pulse conditions.

Tran conductance

/V

I

OUT

ADJ

Accuracy

(d) This current is measured via the collectors and emitters of the switch with these connected to ground (0V)
(e) Measured under pulse conditions. Peak Current = I

ZXLD1322

Document number: DS32166 Rev. 3 - 2

(c)

2 A

30 50 70 mA

10 mA

15 V

50

120
209

116

mV

64 pF
30 ns
28 ns

0 100 200 mV

370
150

350

2.5

ppm/K

KHz
Mhz

) from

(d)

2V<VIN<18V BIAS pin at 0V

R

= 1680

BIAS

IC = 10mA
IC = 0.1A, IB = 10mA
I

= 2A, IB = 50mA

C

IC = 200mA, V
IC = 2A, V
V

CB

CE

= 10V,f = 1MHz
Ic = 0 to IC = 2A V
IC = 2A to Ic < 100A

=V

V
V
V
V

(VIN)

MON
MON
MON
MON

– V

=10mV
=100mV
=10mV
=100mV

M_VIN

CE

= 2V

(e)

= 2V

= 10V

IN

1 mA/V
RM = 0.1

= 100mV

V

MON

= 50mV

V

ADJ

V

= 500mV

ADJ

= 50mV

V

ADJ

V

= 500mV

ADJ

-3 3 %

160
200

275

3

ppm/K

KHz

Mhz
200 µA/V
V

= 500mV

ADJ

C

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-3 3 %

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