PT4115 Datasheet. Www.s Manuals.com. Pt4115e R2.9 Powtech

User Manual: Datasheets PT4115, PT4115B89E, PT4115B89E-B, PT4115BSOH, PT4115BSOH-B.

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PT4115
30V, 1.2A Step-down High Brightness
LED Driver with 5000:1 Dimming
GENERAL DESCRIPTION

FEATURES

The PT4115 is a continuous conduction mode inductive
step-down converter, designed for driving single or
multiple series connected LED efficiently from a
voltage source higher than the total LED chain voltage.
The device operates from an input supply between 6V
and 30V and provides an externally adjustable output
current of up to 1.2A. Depending upon the supply
voltage and external components, the PT4115can
provide more than 30 watts of output power.
The PT4115 includes the power switch and a high-side
output current sensing circuit, which uses an external
resistor to set the nominal average output current, and a
dedicated DIM input accepts either a DC voltage or a
wide range of pulsed dimming. Applying a voltage of
0.3V or lower to the DIM pin turns the output off and
switches the device into a low current standby state.
The PT4115 is available in SOT89-5 and ESOP8
packages.















Simple low parts count
Wide input voltage range: 6V to 30V
Up to 1.2A output current
Single pin on/off and brightness control using DC
voltage or PWM
Up to 1MHz switching frequency
Typical 5% output current accuracy
Inherent open-circuit LED protection
High efficiency (up to 97%)
High-Side Current Sense
Hysteretic Control: No Compensation
Adjustable Constant LED Current
ESOP8 package for large output power application
RoHS compliant

APPLICATIONS








Low voltage halogen replacement LEDs
Automotive lighting
Low voltage industrial lighting
LED back-up lighting
Illuminated signs
SELV lighting
LCD TV backlighting

ORDERING INFORMATION
PACKAGE

TEMPERATURE
RANGE

SOT89-5

-40 oC to 85 oC

ESOP8

-40 oC to 85 oC

ORDERING PART
NUMBER
PT4115B89E:A type
PT4115B89E-B:B type

TRANSPORT
MEDIA
Tape and Reel
1000 units

PT4115BSOH:A type
PT4115BSOH-B:B type

Tape and Reel
2500 units

MARKING
PT4115
xxxxxX
PT4115
xxxxxX

Note:
xxxxxX
Assembly Factory Code
Lot Number

TYPICAL APPLICATION CIRCUIT
VIN

RS

DC6-30V

LED
3W

0.13Ω

L
68uH

D

CIN
AC12-18V

100uF
VIN

DIM

CSN

SW

PT4115
GND

China Resources Powtech (Shanghai) Limited
PT4115_DS Rev EN_2.9

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Page 1

PT4115
30V, 1.2A Step-down High Brightness
LED Driver with 5000:1 Dimming
PIN ASSIGNMENT

1

VIN

2

SW

3

NC

4

PT4115

CSN

8

DIM

7

GNDA

6

GNDP

5

NC

ESOP8

PIN DESCRIPTIONS
PIN No.

PIN
NAMES

1

SW

2

GND

3

DIM

4

CSN

Current sense input

5

VIN

Input Supply Pin. Must be locally bypassed.

-

Exposed

ESOP8 4,5

DESCRIPTION
Switch Output. SW is the drain of the internal N-Ch MOSFET switch.
Signal and power ground. Connect directly to ground plane.
Logic level dimming input. Drive DIM low to turn off the current regulator.
Drive DIM high to enable the current regulator.

PAD

NC

Internally connected to GND. Mount on board for lower thermal resistance.
No connection

ABSOLUTE MAXIMUM RATINGS (note1)
SYMBOL

ITEMS

VALUE

UNIT

VIN

Supply Voltage

-0.3~45

V

SW

Drain of the internal power switch

-0.3~45

V

CSN

Current sense input (Respect to VIN)

+0.3~(-6.0)

V

DIM

Logic level dimming input

-0.3~6

V

Switch output current

1.5

A

Power Dissipation (Note 2)

1.5

W

ISW
PDMAX
PTR

θJA

Thermal Resistance, SOT89-5
θJA

45

o

40

o

C /W

PTR

Thermal Resistance, ESOP8

TJ

Operation Junction Temperature Range

-40 to 150

o

Storage Temperature

-55 to 150

o

TSTG

ESD Susceptibility (Note 3)
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PT4115_DS Rev EN_2.9

2
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C /W
C
C

kV
Page 2

PT4115
30V, 1.2A Step-down High Brightness
LED Driver with 5000:1 Dimming
RECOMMENDED OPERATING RANGE
SYMBOL

ITEMS

VIN

VDD Supply Voltage

TOPT

Operating Temperature

VALUE

UNIT

6 ~ 30

V
o

-40 to +85

C

Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Recommended
Operating Range indicates conditions for which the device is functional, but do not guarantee specific performance
limits. Electrical Characteristics state DC and AC electrical specifications under particular test conditions which
guarantee specific performance limits. This assumes that the device is within the Operating Range. Specifications are
not guaranteed for parameters where no limit is given, however, the typical value is a good indication of device
performance.
Note 2: The maximum power dissipation must be derated at elevated temperatures and is dictated by TJMAX, θJA,
and the ambient temperature TA. The maximum allowable power dissipation is PDMAX = (TJMAX - TA)/ θJA or the
number given in Absolute Maximum Ratings, whichever is lower.
Note 3: Human body model, 100pF discharged through a 1.5kΩ resistor.

ELECTRICAL CHARACTERISTICS (Note 4, 5)
The following specifications apply for VIN=12V, TA=25 oC, unless specified otherwise.
SYMBOL
VIN
VUVLO
VUVLO, HYS
FSW

ITEMS

CONDITIONS

Input Voltage

Min.

Typ.

6

Max.

UNIT

30

V

Under voltage lock out

VIN falling

5.1

V

UVLO hysterisis

VIN rising

500

mV

Max. Switching Frequency

1

MHz

Current Sense
Mean current sense

VCSN
VCSN_hys
ICSN

threshold voltage

VIN-VCSN

A type

95

98

101

mV

B

99

102

105

mV

type

Sense threshold hysteresis
CSN Pin Input Current

±15

%

VIN-VCSN=50mV

8

µA

VDIM<0.3V

95

µA

DIM floating

5

V

Operating Current
IOFF

Quiescent

supply current

with output off

DIM Input
VDIM

Internal supply voltage

VDIM_H

DIM input voltage High

VDIM_L

DIM input voltage Low

VDIM_DC

DC brightness control

fDIM

Max. DIM Frequency
Duty cycle range of low

DPWM_LF

frequency dimming

2.5
0.5
fOSC=500kHz
fDIM =100Hz

0.02%

Brightness control range

China Resources Powtech (Shanghai) Limited
PT4115_DS Rev EN_2.9

V
0.3

V

2.5

V

50

kHz

1
5000:1

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PT4115
30V, 1.2A Step-down High Brightness
LED Driver with 5000:1 Dimming
ELECTRICAL CHARACTERISTICS (Continued) (Note 4, 5)
SYMBOL

ITEMS

CONDITIONS

Min.

Typ.

Max.

UNIT

DIM Input
DPWM_HF

Duty

cycle

range

of

high

frequency dimming

fDIM =20KHz

4%

Brightness control range
RDIM

25:1

DIM pull up resistor to Internal
supply voltage

IDIM_L

1

200

KΩ
uA

DIM input leakage low

VDIM = 0

25

SW On Resistance

VIN=12V

0.6

VIN=24V

0.4

Output Switch
RSW
ISWmean
ILEAK

Continuous SW Current
SW Leakage Current

0.5

Ω
1.2

A

5

µA

Thermal Shutdown
TSD

Thermal Shutdown Threshold

160

℃

TSD-hys

Thermal Shutdown hysteresis

20

℃

Note 4: Typical parameters are measured at 25˚C and represent the parametric norm.
Note 5:

Datasheet min/max specification limits are guaranteed by design, test, or statistical analysis.

SIMPLIFIED BLOCK DIAGRAM

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PT4115_DS Rev EN_2.9

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Page 4

PT4115
30V, 1.2A Step-down High Brightness
LED Driver with 5000:1 Dimming
OPERATION DESCRIPTION
The device, in conjunction with the coil (L1) and

(VDIM) to adjust the output current to a value below the

current sense resistor (RS), forms a self oscillating

nominal average value defined by RS. The DC voltage

continuous-mode buck converter.

is valid from 0.5V to 2.5V. When the dc voltage is

When input voltage VIN is first applied, the initial
current in L1 and RS is zero and there is no output from
the current sense circuit. Under this condition, the
output of CS comparator is high. This turns on an
internal switch and switches the SW pin low, causing
current to flow from VIN to ground, via RS, L1 and the

higher than 2.5V, the output current keeps constant.
The LED current also can be adjusted by a resistor
connected to the DIM pin. An internal pull-up resistor
(typical 200KΩ) is connected to a 5V internal regulator.
The voltage of DIM pin is divided by the internal and
external resistor.

LED(s). The current rises at a rate determined by VIN

The DIM pin is pulled up to the internal regulator (5V)

and L1 to produce a voltage ramp (VCSN) across RS.

by a 200KΩ resistor. It can be floated at normal

When (VIN-VCSN) > 115mV, the output of CS

working. When a voltage applied to DIM falls below

comparator switches low and the switch turns off. The

the threshold (0.3V nom.), the output switch is turned

current flowing on the RS decreases at another rate.

off. The internal regulator and voltage reference remain

When (VIN-VCSN) < 85mV, the switch turns on again

powered during shutdown to provide the reference for

and the mean current on the LED is determined by

the shutdown circuit. Quiescent supply current during

( 85+2115 mV ) / RS = 100mV / RS .

shutdown is nominally 95uA and switch leakage is

The high-side current-sensing scheme and on-board

Additionally, to ensure the reliability, the PT4115 is

current-setting circuitry minimize the number of

built with a thermal shutdown (TSD) protection and a

external components while delivering LED current with

thermal pad. The TSD protests the IC from over

±5% accuracy, using a 1% sense resistor.

temperature (160℃). Also the thermal pad enhances

The PT4115 allow dimming with a PWM signal at the

power dissipation. As a result, the PT4115 can handle a

DIM input. A logic level below 0.3V at DIM forces

large amount of current safely.

below 5uA.

PT4115 to turn off the LED and the logic level at DIM
must be at least 2.5V to turn on the full LED current.
The frequency of PWM dimming ranges from 100Hz to
more than 20 kHz.
The DIM pin can be driven by an external DC voltage

China Resources Powtech (Shanghai) Limited
PT4115_DS Rev EN_2.9

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Page 5

PT4115
30V, 1.2A Step-down High Brightness
LED Driver with 5000:1 Dimming
TYPICAL PERFORMANCE CHARACTERISTICS

Efficiency1,3 and 7 LEDs

100%

L=47uH
Rs=0.13ohm
7LEDs

Efficiency

95%
90%

3 LEDs

85%
80%
75%

1LED

8

10 12 14 16 18 20 22 24 26 28 30

Supply Voltage Vin(V)

Vdim vs Supply Voltage

5.5
5.4
5.3

Vdim(V)

5.2
5.1
5.0
4.9
4.8
4.7
4.6
4.5

5

10

15

20

25

30

Supply Voltage Vin(V)
Vdim vs Temperature

5.30

Vdim(V)

5.25
5.20
5.15
5.10
5.05
5.00

-40 -20

0

20

40

60

80 100 120

Temperature(Deg C)

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Page 6

PT4115
30V, 1.2A Step-down High Brightness
LED Driver with 5000:1 Dimming
Rsw vs Supply Voltage

1.0

Rsw (ohm)

0.9
0.8
0.7
0.6
0.5
0.4
0.3

5

15

25

35

Supply Voltage Vin(V)

Supply Current vs Supply Voltage

250

Iin (uA)

200
150
100
50
0

0

5

10

15

20

25

30

Supply Voltage Vin(V)

LED Current vs Vdim

800

LED current (mA)

700

R=0.13ohm

600
500
400
300
R=0.33ohm

200
100
0
0

1

2

3

4

Dim Pin Voltage (V)

China Resources Powtech (Shanghai) Limited
PT4115_DS Rev EN_2.9

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Page 7

5

PT4115
30V, 1.2A Step-down High Brightness
LED Driver with 5000:1 Dimming
Output Current L=27uH Rcs=0.0825ohm

Output Current Deviation

Output Current

1.22
1.20
1.18

4LEDs

1.16
1.14
7LEDs

6LEDs
1LED
2LEDs

1.12
1.10

5

5LEDs
3LEDs

10

15

20

25

Output Current L=27uH Rcs=0.0825ohm

3%

1.24

2%
1%
0%
-1%
-3%
-4%
-5%
-6%

1LED
5LEDs

-7%
-8%

30

4LEDs

-2%

2LEDs

5

3LEDs

10

15

Supply Voltage(V)

2LEDs

Duty Cycle

80%
70%

4LEDs

5LEDs

6LEDs

7LEDs

1LED

50%
40%
30%
20%
10%

900
800
700
600
500
400

10

15

20

25

4LEDs

300

7LEDs

30

5

10

Output Current L=47uH Rcs=0.13ohm
Output Current Deviation

Output Current(mA)

780
770
760
750
740

7LEDs

710

4LEDs

2LEDs

720

5LEDs

6LEDs

3LEDs

10

15

20

PT4115_DS Rev EN_2.9

30

2%
0%

25

30

7LEDs

-2%
1LED

-4%

4LEDs 5LEDs 6LEDs

2LEDs
3LEDs

5

10

15

20

25

30

Supply Voltage(V)

Supply Voltage Vin(V)

China Resources Powtech (Shanghai) Limited

25

4%

-6%
5

20

Output Current L=47uH Rcs=0.13ohm

6%

790

730 1LED

15

Supply Voltage Vin(V)

Supply Voltage Vin(V)
800

5LEDs 6LEDs

200 1LED
2LEDs 3LEDs
100
0

5

30

Switching Frequency L=27uH R=0.0825ohm

60%

0%

25

1000

Switching Frequency(kHZ)

3LEDs

90%

20

Supply Voltge(V)

Duty Cycle L=27uH R=0.0825ohm

100%

6LEDs 7LEDs

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Page 8

PT4115
30V, 1.2A Step-down High Brightness
LED Driver with 5000:1 Dimming
Duty Cycle L=47uH Rcs=0.13ohm
3LEDs

90%

5LEDs

Switch Frequency L=47uH Rcs=0.13ohm
900

6LEDs

Switch Frequency(kHz)

100%

7LEDs

4LEDs

Duty Cycle

80% 2LEDs
70%
60%
50%
40%
30%

1LED

20%
10%

800
700
600
500
400

1LED
4LEDs

300

5LEDs

2LEDs

200

6LEDs

3LEDs

100
7LEDs

0%

8

0

10 12 14 16 18 20 22 24 26 28 30

8

10

12

Supply Voltage Vin(V)

14

16

18

20

22

24

26

28

30

Supply Voltage Vin(V)
Output Current L=100uH Rcs=0.33ohm
Output Current Deviation

8%
6%
4%
2%
0%
-2%
1LED

-4%
-6%

2LEDs
4LEDs

3LEDs

5

10

15

5LEDs

20

6LEDs

7LEDs

25

30

Supply Voltage
Duty Cycle L=100uH R=0.33ohm
80%

3LEDs

Duty Cycle

70%

5LEDs
4LEDs

6LEDs

1000

7LEDs

Switch Frequency(kHz)

90%

2LEDs

60%
50%

1LED

40%
30%
20%
10%
0%

5

10

15

20

25

Supply Voltage Vin(V)

China Resources Powtech (Shanghai) Limited
PT4115_DS Rev EN_2.9

30

Switch Frequency L=100uH R=0.33ohm

900
800
700
600
500

2LEDs

4LEDs

400
300

7LEDs

3LEDs

1LED

200

5LEDs 6LEDs

100
0

5

10

15

20

25

30

Supply Voltage Vin(V)

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PT4115
30V, 1.2A Step-down High Brightness
LED Driver with 5000:1 Dimming

China Resources Powtech (Shanghai) Limited
PT4115_DS Rev EN_2.9

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Page 10

PT4115
30V, 1.2A Step-down High Brightness
LED Driver with 5000:1 Dimming
APPLICATION NOTES
Setting nominal average output current with
external resistor RS
The nominal average output current in the LED(s) is
determined by the value of the external current sense
resistor (RS) connected between VIN and CSN and is
given by:

I OUT  0.1 / Rs

( Rs  0.082)

This equation is valid when DIM pin is float or applied
with a voltage higher than 2.5V (must be less than 5V).
Actually, RS sets the maximum average current which
can be adjusted to a less one by dimming.

cycle PWM can be applied to the DIM pin, as shown
below, to adjust the output current to a value below the
nominal average value set by resistor RS:

I OUT 

0.1  D
Rs

(0  D  100%,2.5V  V pulse  5V )

I OUT 

V pulse  0.1  D
2.5  Rs

(0  D  100%,0.5V  V pulse  2.5V )

Output current adjustment by external DC control
voltage
The DIM pin can be driven by an external dc voltage
(VDIM), as shown, to adjust the output current to a
value below the nominal average value defined by RS.

RS

VIN
0.13Ω

LED
3W
L
68uH

D

RS

VIN
0.13Ω

LED
3W

VIN

L
68uH

D

DIM

CSN

SW

PT4115
GND

VIN

DIM

CSN

SW

PT4115
GND

The average output current is given by:

I OUT 

0.1  VDIM
(0.5V  VDIM  2.5V )
2.5  Rs

Note that 100% brightness setting corresponds to:

(2.5V  VDIM  5V )
Output current adjustment by PWM control
A Pulse Width Modulated (PWM) signal with duty

China Resources Powtech (Shanghai) Limited
PT4115_DS Rev EN_2.9

PWM dimming provides reduced brightness by
modulating the LED’s forward current between 0% and
100%. The LED brightness is controlled by adjusting
the relative ratios of the on time to the off time. A 25%
brightness level is achieved by turning the LED on at
full current for 25% of one cycle. To ensure this
switching process between on and off state is invisible
by human eyes, the switching frequency must be
greater than 100 Hz. Above 100 Hz, the human eyes
average the on and off times, seeing only an effective
brightness that is proportional to the LED’s on-time
duty cycle. The advantage of PWM dimming is that the
forward current is always constant, therefore the LED
color does not vary with brightness as it does with
analog dimming. Pulsing the current provides precise
brightness control while preserving the color purity.
The dimming frequency of PT4115 can be as high as 20
kHz.

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PT4115
30V, 1.2A Step-down High Brightness
LED Driver with 5000:1 Dimming
Shutdown mode
Taking the DIM pin to a voltage below 0.3V will turn
off the output and the supply current will fall to a low
standby level of 95μA nominal.
Soft-start
An external capacitor from the DIM pin to ground will
provide additional soft-start delay, by increasing the
time taken for the voltage on this pin to rise to the
turn-on threshold and by slowing down the rate of rise
of the control voltage at the input of the comparator.
Adding capacitance increases this delay by
approximately 0.8ms/nF.
Inherent open-circuit LED protection
If the connection to the LED(s) is open-circuited, the
coil is isolated from the SW pin of the chip, so the
device and LED will not be damaged.

lower efficiency. Higher values of inductance also
result in a smaller change in output current over the
supply voltage range. (See graphs). The inductor should
be mounted as close to the device as possible with low
resistance connections to the SW and VIN pins.
The chosen coil should have a saturation current higher
than the peak output current and a continuous current
rating above the required mean output current.
Following table gives the guideline on inductor
selection:
Load current Inductor
Saturation current
Iout>1A

27-47uH

0.8A
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