A Product Line of
Diodes Incorporated
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.
Pin Assignments
Top View
TSOT25
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
Applications
Low voltage halogen replacement LEDs
Low voltage industrial lighting
LED back-side lighting
Illuminated signs
PAM2861
Document number: DSxxxxx Rev. 1 - 1
1 of 12
www.diodes.com
July 2013
© Diodes Incorporated
A Product Line of
Diodes Incorporated
PAM2861
Typical Applications Circuit
Pin Descriptions
Pin
Number
1
2
Pin
Name
LX
GND
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
OUT
nom
• Drive with PWM signal from open-collector or open-drain transistor, to adjust output current. Adjustment range
1% to 100% of I
OUT
nom for f < 500Hz
• 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
I
OUT
nom = 0.1/Rs
Input voltage (6V to 40V). Decouple to ground with 10μF or higher X7R ceramic capacitor close to device.
3
VSET
4
5
ISENSE
VIN
PAM2861
Document number: DSxxxxx Rev. 1 - 1
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July 2013
© Diodes Incorporated
A Product Line of
Diodes Incorporated
PAM2861
Functional Block Diagram
Absolute Maximum Ratings
(@T
A
= +25°C, unless otherwise specified.)
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
Input Voltage Range
LX, I
SENSE
Pin Voltage
VSET Pin Voltage
Maximum Junction Temperature
Storage Temperature
Soldering Temperature
Rating
-0.3 to +40
-0.3 to +40
-0.3 to +6.0
170
-65 to +170
300, 5sec
Unit
V
°C
Recommended Operating Conditions
(@T
A
= +25°C, unless otherwise specified.)
Parameter
Input Voltage Range
Ambient Temperature Range
Junction Temperature Range
Rating
6 to 40
-40 to +85
-40 to +150
Unit
V
°C
PAM2861
Document number: DSxxxxx Rev. 1 - 1
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July 2013
© Diodes Incorporated
A Product Line of
Diodes Incorporated
PAM2861
Thermal Information
Parameter
Thermal Resistance (Junction to Ambient)
Thermal Resistance (Junction to Case)
Package
TSOT25
SOT89-5
TSOT25
SOT89-5
Symbol
θ
JA
θ
JC
Max
250
160
130
45
Unit
°C/W
Electrical Characteristics
(@T
A
= +25°C, V
IN
= 16V, unless otherwise specified.)
Parameter
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
Max Duty Circle
Recommended Duty Cycle Range
Internal Comparator Propagation Delay
Over Temperature Protection
Temp Protection Hysteresis
Current Limit
Note:
Symbol
V
IN
I
LED
I
SD
I
Q
V
SENSE
V
SENSE_HYS
I
SENSE
V
EN
V
EN(ON)
V
EN(OFF)
R
LX
I
LX(LEAK)
T
SS
F
LX
T
ON_REC
F
LX(MAX)
Test Conditions
R
S
= 0.3Ω
R
S
= 0.1Ω
VSET Pin Grouded
VSET Pin Floating, V
IN
= 16V
Measured on I
SENSE
Pin with
Respect to V
IN
V
SENSE
= V
IN
-0.1
For DC Dimming
V
EN
Rising
V
EN
Falling
@I
LX
= 100mA
V
IN
= 16V, C
EN
= 1nF
V
I
= 16V, V
O
= 9.6V (3 LEDs)
L = 47µF,
ΔI
= 0.25A (I
LED
= 1A)
For 4% Accuracy
Min
6
Typ
333
1
20
0.6
Max
40
Units
V
mA
A
40
µA
mA
95
100
±13
8
105
mV
%
µA
0.3
0.25
0.2
0.3
2.5
V
V
V
Ω
5
1.5
233
500
1.0
98
25
45
150
40
Peak Inductor Current
1.5
75
µA
ms
kHz
Ns
MHz
%
%
ns
°C
°C
A
D
LX
T
PD
(Note 1)
T
OTP
T
OTP_HYS
I
XL(MAX)
1. Parameters are not tested at production, but guaranteed by design. V
SENSE
: level A: 95mV to 100mV; level B: 100mV to 105mV.
PAM2861
Document number: DSxxxxx Rev. 1 - 1
4 of 12
www.diodes.com
July 2013
© Diodes Incorporated
A Product Line of
Diodes Incorporated
PAM2861
Typical Performance Characteristics
(@T
A
= +25°C, V
IN
= 16V, unless otherwise specified.)
PAM2861
Document number: DSxxxxx Rev. 1 - 1
5 of 12
www.diodes.com
July 2013
© Diodes Incorporated
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