UM1360 EVB User’s Guide
UM1360
Evaluation Board
User’s Guide
Version
Date
1.0
2012-11-02
Provider
LB
http://www.union-ic.com
Approve
Note
Initial version.
UM1360 EVB User’s Guide
Table of Contents
1. Board Information
1.1 Schematic
1.2 PCB Layout
1.3 Jumper and Test Point Definition
2. Board Operation
2.1 Power and Load Connection
2.2 LED Current Setting
2.3 Shutdown and Dimming
3. Board Component
3.1 Sense Resistor
3.2 Inductor
4. Temperature Compensation
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UM1360 EVB User’s Guide
1
Board Information
The UM1360 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. UM1360 EVB is an evaluation test platform. The board
can demonstrate the main function of the chip, allowing users to fully experience the
advantages of using the chip. The board also can be used for testing the chip
performance by modifying some peripheral component parameters. The user can
verify the circuit characteristics and parameters with the board to ensure the practical
application of user interests.
1.1 Schematic
1
2
R1
VIN
TP3
0.1R
D1
SS14
D2
SS14
C1
50V/100uF
4
GND
U1
UM1360
LED+
J3
LED
GND
LEDVSET
TP7
C3
100nF
LX
LX
TP8
GND
L1
LX
47uH
Fig 1.1 UM1360 EVB schematic
1.2 PCB Layout
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1
2
C2
1uF
3
D5
SS14
1
D4
SS14
VIN
TP2
D3
SS14
2
DC/AC
VIN
GND
TP1
LX
AC+
AC-
ISENSE
VIN
J2
1
2
LED+
LED+
TP4
5
DC
VSET
J1
R2
NTC
TP5
LED-
LED-
UM1360 EVB User’s Guide
Fig 1.2
Fig 1.3
UM1360 EVB PCB Top Layer
UM1360 EVB PCB Bottom Layer
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UM1360 EVB User’s Guide
1.3 Jumper and Test Point Definition
Jumper
Description
J1
DC Power supply input
J2
AC Power supply input
J3
LED drive output.
Test Point
6V to 40V power supply
Connect to single or multiple
series LEDs
Description
TP1
VIN pin test point
TP3
LED+ test point
TP5
LED- test point
TP7
LX pin test point
TP2,TP4,TP8
Note
Note
Test points
GND points
Tab 1.1 UM1360 EVB Jumper and Test Point Definition
2
Board Operation
When using UM1360 EVB, you need to properly connect an external power supply
and external LED load. Fig 2.1 shows typical switching and LED current operation
waveforms
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UM1360 EVB User’s Guide
Fig 2.1 Typical Switching Operation Waveforms (3 LEDs,100uH,Vin=16V,Rs=0.33Ω)
2.1 Power and Load Connection
Connect DC power supply to J1 or AC power supply to J2. The power supply voltage
range: 6.0V - 40.0V.
When using power supply, you need to confirm current limit setting have enough
allowance. Input power cable should be thicker to reduce the loss of input voltage
when the load current is larger.
Connect external LEDs across pins ‘LED+’ and ‘LED-’. ‘LED+’ is the LEDs’ anode
connection point and ‘LED-’ is the LEDs’ cathode connection point. The number of
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UM1360 EVB User’s Guide
external LEDs that can be connected depends on their operating power and forward
voltage drop. For an external load other than LEDs, the positive terminal of the load
should be connected to test pin ‘LED+’ and the negative terminal of the load should
be connected to test pin ‘LED-’.
2.2 LED Current Setting
For changing the LED current, you need to follow these steps:
1. Remove R1.
2. Calculate and fit a new sense resistor, R1, the value of which is based on the
required LED current without dimming. R1 can be calculated using following
equation :
R1 = 0.1V/IOUT
where
IOUT = the LED current.
R1 = the sense resistor value in ohms.
0.1V is the nominal sense voltage with ‘VSET’ open circuit or set to 2.5V.
2.3 Shutdown and Dimming
The VSET pin is a Multi-function On/Off and brightness control pin:
Leave the VSET pin floating for normal operation.
Driving the VSET pin below 0.2V will shutdown the output current and the supply
current will fall to a low standby level of 20μA nominal. So shorting R2 will make
the chip into shutdown mode.
For DC dimming, the VSET pin may be driven between 0.3V and 2.5V.
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UM1360 EVB User’s Guide
LED Current vs VSET
(Vin=16V,3LEDs,100uH,Rs=0.33Ω)
350
300
ILED(mA)
250
200
150
100
50
0
0
0.5
1
1.5
2
2.5
3
VSET(V)
Fig 2.2 DC Dimming
For PWM dimming, an external open-collector NPN transistor or open-drain
N-channel MOSFET can be used to drive the VSET pin. The PWM frequency should
be low, around 100Hz to 500 Hz.
LED Current vs VSET Duty Cycle
(Vin=16V,3LEDs,100uH,Rs=0.33Ω)
350
300
ILED(mA)
250
200
PWM=100Hz
150
100
50
0
0
10
20
30
40
50
60
Duty Cycle(%)
Fig 2.3 PWM Dimming
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70
80
90
100
UM1360 EVB User’s Guide
3
Component
Board Component
Description
Recommended Part No.
U1
LED Driver Chip
R1
Resistor, 0R1, 1%, 0805
L1
Inductor,47uH, 2A, CDRH
C1
Capacitor, Electrolytic,100uF/50V
C2
Capacitor, Ceramic, 1uF/50V, 0805
C3
Capacitor, Ceramic, 0.1uF/50V, 0805
D1, D2,
D3, D4, D5
UM1360
Schottky diodes,SMT
SS14
Tab 3.1 UM1360 EVB BOM List
3.1 Sense Resistor
In order to ensure accuracy of LED current setting, recommend using 1% precision of
sense resistor.
3.2 Inductor
The system efficiency depends on the sense resistor, supply voltage, switching
inductor and the number of LEDs.
Following table gives the guideline on inductor selection:
Load Current
Inductor
Saturation Current
Iout>1A
27-47uH
1.3-1.5 times of load current
0.8A<Iout≤1A
33-82uH
0.4A<Iout≤0.8A
47-100uH
Iout≤0.4A
68-220uH
Tab 3.2
Recommended Inductor Value List
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UM1360 EVB User’s Guide
4
Temperature Compensation
High luminance LEDs often need to be supplied with a temperature compensated
current in order to maintain stable and reliable operation at all drive levels. The LEDs
are usually mounted remotely from the device. So, for this reason, the temperature
coefficients of the internal circuits for the UM1360 have been optimized to minimize
the change in output current when no compensation is employed. If output current
compensation is required, it is possible to use an external temperature sensing
network - normally using Negative Temperature Coefficient (NTC) thermistors
and/or diodes, mounted very close to the LED(s). The output of the sensing network
can be used to drive the VSET pin in order to reduce output current with increasing
temperature.
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