Diodes PAM2861 User Manual

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PAM2861

1A LED DRIVER WITH INTERNAL SWITCH

Description

The PAM2861 is a continuous mode inductive step-down converter, designed for driving single or multiple series connected LEDs efficiently from a voltage source higher than the LED voltage. The device operates from an input supply between 6V and 40V and provides an externally adjustable output current of up to 1A. Depending upon supply voltage and external components, this can provide up to 30 watts of output power.

The PAM2861 includes the output switch and a high-side output current sensing circuit, which uses an external resistor to set the nominal average output current.

Output current can be adjusted below the set value, by applying an external control signal to the VSET pin.

The VSET pin will accept either a DC voltage or a PWM waveform.

The soft-start time can be increased using an external capacitor from the VSET pin to ground. Applying a voltage of 0.2V or lower to the VSET pin turns the output off and switches the device into a low current standby state.

Features

 Simple Low Parts Count  Internal 40V NDMOS Switch  1A Output Current  Single Pin On/Off and Brightness Control Using DC Voltage or

PWM

 Soft-Start  High Efficiency (up to 97%)  Wide Input Voltage Range: 6V to 40V  Output Shutdown  Open LED Protection  Short LED Protection  Up to 1MHz Switching Frequency  Inherent Open-Circuit LED Protection  Typical 5% Output Current Accuracy  Pb-free TSOT25 and SOT89-5 Packages

Pin Assignments

Top View

TSOT25

Applications

 Low voltage halogen replacement LEDs  Low voltage industrial lighting  LED back-side lighting  Illuminated signs

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Typical Applications Circuit

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PAM2861

Pin Descriptions

Number

1 LX 2 GND

3 VSET

4 ISENSE 5 VIN

Name

Function

Drain of NDMOS switch. Ground (0V)

• Multi-function On/Off and brightness control pin:

• Leave floating for normal operation.

• Drive to voltage below 0.2V to turn off output current

• Drive with DC voltage (0.3V < VSET< 2.5V) to adjust output current from 12% to 100% of I

• Drive with PWM signal from open-collector or open-drain transistor, to adjust output current. Adjustment range 1% to 100% of I

• Connect a capacitor from this pin to ground to increase soft-start time. (Default soft-start time = 0.1ms. Additional soft-start time is approx.1.5ms/1nF)

Connect resistor RS from this pin to VIN to define nominal average output current

nom = 0.1/Rs

I

OUT

Input voltage (6V to 40V). Decouple to ground with 10F or higher X7R ceramic capacitor close to device.

nom for f < 500Hz

OUT

nom

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Functional Block Diagram

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PAM2861

Absolute Maximum Ratings (@T

These are stress ratings only and functional operation is not implied. Exposure to absolute maximum ratings for prolonged time periods may affect device reliability. All voltages are with respect to ground.

Parameter Rating Unit

Input Voltage Range -0.3 to +40 LX, I VSET Pin Voltage -0.3 to +6.0 Maximum Junction Temperature 170 Storage Temperature -65 to +170

Soldering Temperature 300, 5sec

SENSE

Pin Voltage

Recommended Operating Conditions (@T

Parameter Rating Unit

Input Voltage Range 6 to 40 V Ambient Temperature Range -40 to +85 °C Junction Temperature Range -40 to +150

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= +25°C, unless otherwise specified.)

A

-0.3 to +40

= +25°C, unless otherwise specified.)

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V

°C

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PAM2861

Thermal Information

Parameter Package Symbol Max Unit

Thermal Resistance (Junction to Ambient)

Thermal Resistance (Junction to Case)

TSOT25

SOT89-5 160

TSOT25

SOT89-5 45



JA



JC

Electrical Characteristics (@T

= +25°C, VIN = 16V, unless otherwise specified.)

A

Parameter Symbol Test Conditions Min Typ Max Units

Input Voltage Output Current Shutdown Current

Quiescent Current without Switching Mean Current Sense Threshold Voltage Sense Threshold Hysteresis

ISENSE Pin Input Current VSET Range on VSET Pin DC Voltage on VSET Pin to Enable DC Voltage on VSET Pin to Disable

LX Switch On Resistance LX Switch Leakage Current Soft Start Time

Operating Frequency Recommended Minimum Switch ON Time

Recommended Maximum Switch Frequency

V

IN

I

LED

I

SD

I

VSET Pin Floating, VIN = 16V

Q

V

SENSE

V

SENSE_HYS

I

SENSE

V

EN

V

EN(ON)

V

EN(OFF)

@ILX = 100mA

R

LX

I

LX(LEAK)

VIN = 16V, CEN = 1nF

T

SS

F

LX

T

ON_REC

F

LX(MAX)

= 0.3

R

S

RS = 0.1 VSET Pin Grouded 20 40 µA

Measured on I Respect to V

±13 %

V

SENSE

IN

= VIN -0.1

For DC Dimming 0.3 2.5 V

VEN Rising

VEN Falling

5 µA

= 16V, VO = 9.6V (3 LEDs)

V

I

L = 47µF, I = 0.25A (I For 4% Accuracy 500 Ns

1.0 MHz Max Duty Circle 98 % Recommended Duty Cycle Range Internal Comparator Propagation Delay Over Temperature Protection Temp Protection Hysteresis Current Limit

Note: 1. Parameters are not tested at production, but guaranteed by design. V

T

PD

T

OTP_HYS

I

XL(MAX)

D

LX

(Note 1) T

OTP

25 75 % 45 ns 150 °C 40 °C Peak Inductor Current 1.5 A

: level A: 95mV to 100mV; level B: 100mV to 105mV.

SENSE

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SENSE

250

130

Pin with

= 1A)

LED

°C/W

6 40 V

333 mA 1 A

0.6 mA

95 100 105 mV

8 µA

0.25 V

0.2 V

0.3 

1.5 ms 233 kHz

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