cd00204076

AN2809
Application note
6-row / 30-mA LED driver with boost converter
for the backlight of LCD panels
Introduction
The LED7706 consists of a high-efficiency monolithic boost converter and six controlled
current generators (rows) specifically designed to supply the LED arrays used in the
backlights of LCD panels. The device can manage an output voltage of up to 36 V (ten white
LEDs per row).
The generators can be externally-programmed to sink up to 30 mA and can be dimmed via
a PWM signal (a 1% dimming duty-cycle at 20 kHz can be managed). The device detects
and manages the open and shorted LED faults and leaves unused rows floating. Basic
protections (output over-voltage, internal MOSFET over-current and thermal shutdown) are
provided.
Figure 1.
February 2009
LED7706 demonstration board
Rev 2
1/22
www.st.com
Contents
AN2809
Contents
1
LED7706 main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1
Boost section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.2
Backlight driver section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2
LED7706 demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3
Component list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4
Components assembly and layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5
I/O interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
6
Recomended equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
7
Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
7.1
SW1 fixed or adjustable switching frequency (FSW pin) . . . . . . . . . . . . . 10
7.2
SW2 fault management mode (MODE pin) . . . . . . . . . . . . . . . . . . . . . . . 11
7.3
SW3 enable function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
8
Test setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
9
Getting started . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
9.1
Quick startup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
9.2
Open and shorted WLEDs fault testing . . . . . . . . . . . . . . . . . . . . . . . . . . 14
9.3
Device synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
9.4
Efficiency measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
10
WLEDs test board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
11
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2/22
AN2809
List of figures
List of figures
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Figure 12.
Figure 13.
Figure 14.
LED7706 demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
LED7706 board schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Top side component placement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Bottom side test points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
SW1 (FSW) setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
SW2 (MODE) setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
LED7706 demonstration board and white LEDs test board assembly . . . . . . . . . . . . . . . . 12
LED7706 board test setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
LED7706 synchronization setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Efficiency measurements setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Efficiency vs DIM duty cycle, VIN=12V, 10 white LEDs in series, IOUT = 120mA . . . . . . . . 17
Efficiency vs DIM duty cycle, VIN=24V, 10 white LEDs in series, IOUT = 120mA . . . . . . . . 17
WLEDs test board. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
WLEDs test board schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3/22
List of tables
AN2809
List of tables
Table 1.
Table 2.
Table 3.
Table 4.
Table 5.
Table 6.
Table 7.
Table 8.
4/22
LED7706 performance summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
LED7706 component list. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
LED7706 demonstration board test points description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Faults management summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Test board jumpers function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Test boards switches functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Test board test-points function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
AN2809
LED7706 - main features
1
LED7706 - main features
1.1
Boost section
1.2
●
4.5- to 36-V input voltage range
●
Internal power MOSFET
●
Internal +5 V LDO for device supply
●
Up to 36-V output voltage
●
Constant frequency peak current-mode control
●
200-kHz to 1-MHz adjustable switching frequency
●
External sync for multi-device application
●
Pulse-skip power-saving mode at light loads
●
Programmable soft-start
●
Programmable OVP protection
●
Single ceramic output capacitor
●
Non-latched thermal shutdown
Backlight driver section
●
Six rows with 30 mA maximum current capability (adjustable)
●
Up to 10 white LEDs per row
●
Row disabling option
●
Less than 500 ns minimum dimming time (1% minimum dimming duty-cycle at 20 kHz
dimming frequency)
●
±2.0% current matching between rows
●
LED failure (open and short circuit) detection
5/22
LED7706 demonstration board
2
AN2809
LED7706 demonstration board
The LED7706 demonstration board has been designed to manage six strings of 8 to 10
white LEDs each.
Table 1 summarizes the board features and Figure 2 shows the schematic of the LED7706
demonstration board. The input voltage range is limited to 32 V because of the 35 V rated
input capacitor. Extended operating input voltage ranges (up to 36 V) can be achieved by
using a 50-V rated MLCC.
Table 1.
LED7706 performance summary
Parameter
Conditions
Value
Minimum input voltage
4.5 V
Maximum input voltage
32 V
Output voltage
VIN<VBOOST<36 V
Output OVP threshold
R1 = 510 kΩ, R2 = 16 kΩ
38 V
Internal MOSFET OCP
R7 = 180 kΩ
3.3 A
FSW pin to AVCC
660 kHz
FSW pin to R5 = 330 kΩ
825 kHz
400 Hz < FDIM < 20 kHz
500 ns
Boost section switching frequency
Minimum dimming on-time
19.6 mA
Output current (each row)
R6=51 kΩ
Output current accuracy
±2.0%
VIN = 12 V, VBOOST = 34 V,
FSW = 660 kHz
Efficiency
Figure 2.
91%
LED7706 board schematic
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6/22
AN2809
Component list
3
Component list
Table 2.
LED7706 component list
Qty Component
Description
Package
Part number
MFR
Value
UMK325BJ106KM-T
Taiyo
Yuden
10µF
GRM31CR71H475KA88B
MURATA
1
C1
Ceramic, 35V, X5R, 20%
SMD 1210
1
C2
Ceramic, 50V, X7R, 20%
SMD 1206
4.7µF
2
C3, C4
Ceramic, 50V, X7R, 20%
SMD 1206
N.M.
1
C5
Ceramic, 25V, X5R, 20%
SMD 0603
Standard
1µF
1
C6
Ceramic, 25V, X5R, 20%
SMD 0603
Standard
100nF
1
C7
Ceramic, 25V, X5R, 20%
SMD 0603
Standard
3.3nF
1
C8
Ceramic, 25V, X5R, 20%
SMD 0603
Standard
4.7nF
1
C9
Ceramic, 25V, X5R, 20%
SMD 0603
Standard
N.M.
1
C10
Ceramic, 25V, X5R, 20%
SMD 0402
Standard
220pF
1
C11
Ceramic, 25V, X5R, 20%
SMD 0603
Standard
4.7nF
1
R1
Chip resistor, 0.1W, 1%
SMD 0603
Standard
510kΩ
1
R2
Chip resistor, 0.1W, 1%
SMD 0603
Standard
16kΩ
1
R3
Chip resistor, 0.1W, 1%
SMD 0603
Standard
2.4kΩ
1
R4
Chip resistor, 0.1W, 1%
SMD 0603
Standard
4.7Ω
1
R5
Chip resistor, 0.1W, 1%
SMD 0603
Standard
330kΩ
1
R6
Chip resistor, 0.1W, 1%
SMD 0603
Standard
51kΩ
1
R7
Chip resistor, 0.1W, 1%
SMD 0603
Standard
180kΩ
1
R8
Chip resistor, 0.1W, 1%
SMD 0603
Standard
680kΩ
2
R9, R10
Chip resistor, 0.1W, 1%
SMD 0603
Standard
100kΩ
1
R11
Chip resistor, 0.1W, 1%
SMD 0603
Standard
1.2kΩ
1
L1
6µ8, 75mH, 2.7A
6x6mm
LPS6235-682MLC
Coilcraft
6.8µH
1
D1
Schottky, 40V, 1A
DO216-AA
STPS1L40M
ST
STPS1L40M
1
D2
Red LED, 3mA
SMD 0603
1
U1
Integrated circuit
QFN4x4
1
J2
PCB pad jumper
1
J8
Header 8
SIL 8
Standard
1
SW1, SW2
Jumper 3
SIL 3
Standard
1
SW3
Pushbutton
6x6mm
Standard
LED7706
FSM4JSMAT
ST
LED7706
TYCO
7/22
Component assembly and layout
4
8/22
Component assembly and layout
Figure 3.
Top side component placement
Figure 4.
Bottom side test points
AN2809
AN2809
5
I/O interface
I/O interface
The LED7706 demonstration board has the following test points.
Table 3.
Description of LED7706 demonstration board test points
Test point
Description
VIN+
Input voltage, positive terminal
VIN-
Input voltage, negative terminal
GND
Reference ground
Row1 to row6
VBOOST
Current generators output
Boost regulator output voltage
DIM
PWM dimming input
EN
Enable input (active high)
SYNC
Synchronization output
FSW
Synchronization input
FAULT
Fault signal, active low
9/22
Recommended equipment
6
7
AN2809
Recommended equipment
●
4.5–32 V, 2 A capable power supply.
●
Digital multimeters.
●
200 MHz oscilloscope.
●
Signal generators for PWM dimming and synchronization clock (optional).
Configuration
The LED7706 demonstration board allows the user to select the desired mode of operation
using the SW1 and SW2 selectors. Refer to the following configuration description. A red
LED is connected to the FAULT pin to easily monitor its status; if this option is not desired,
the monitor LED can be disconnected by opening the J2 jumper.
7.1
SW1 fixed or adjustable switching frequency (FSW pin)
The SW1 selector is used to choose between the fixed switching frequency (660 kHz) and a
user-defined switching frequency in the range of 200 kHz to 1 MHz. When connected in the
lower position, the fixed switching frequency is selected.
If SW1 is in the upper position, the switching frequency is given by:
F SW = 2.5 ⋅ R 5
Figure 5.
SW1 (FSW) setting
!DJUSTABLE3WITCHINGFREQUENCY
&IXED3WITCHING&REQUENCY
DEFAULTPOSITION
!-V
The R5 resistor is set to 330 kΩ (FSW = 825 kHz).
7.2
SW2 fault management mode (MODE pin)
The SW2 selector is used to connect the MODE to AVCC or ground. When the jumper is set
to the upper position, the MODE pin is connected to ground and the corresponding fault
management is summarized in the first column of Table 4.
10/22
AN2809
Configuration
Otherwise, when SW2 is set to the lower position, the MODE pin is connected to AVCC and
the corresponding fault management is summarized in the second column of Table 4.
Figure 6.
SW2 (MODE) setting
02'(SLQWRJURXQG
VHH7DEOHVW FROXPQ
02'(SLQWR$9&&
VHH7DEOHQG FROXPQ
!-V
Table 4.
Fault management summary
Fault
7.3
MODE to GND
MODE to VCC
Internal MOSFET over
current
Fault pin HIGH
Power MOSFET turned OFF
Output overvoltage
FAULT pin LOW
Device turned OFF, latched condition
Thermal shutdown
FAULT pin LOW. Device turned OFF.
Automatic restart after 30°C temperature drop.
LED short circuit
Fault pin LOW
Device turned OFF at first
occurrence, latched condition
(Vth=3.4V)
Fault pin LOW
Faulty row(s) disconnected. Device
keeps on working with the remaining
row(s) (Vth=6V)
Open row(s)
Fault pin LOW
Device turned OFF at first
occurrence, latched condition
FAULT pin HIGH
Faulty row(s) disconnected. Device
keeps on working with the remaining
row(s)
SW3 enable function
The terminals of the switch SW3 are connected on one side to the EN pin and on the other
side to ground. Therefore, when the switch is not pressed, the EN pin is floating, which
implies that the device is working. When the SW3 pin is pressed, the EN pin is connected to
ground. When the SW3 is released, the device re-starts (the soft-start is performed). The
SW3 switch can be activated whenever a new start-up is required or to escape a latched
condition.
11/22
Test setup
8
AN2809
Test setup
A proper WLED array is required as load to correctly evaluate the LED7706. Figure 7 shows
a possible assembly of LED7706 with a WLEDs test board. This demonstration board
includes 60 white LEDs (20 mA), switches, jumpers and test points used to easily perform
the functional tests of the LED7706. Chapter 10 provides a brief description of the test
board and its schematic, which can be used as reference for any customized board.
Figure 7.
LED7706 demonstration board and white LEDs test board assembly
Figure 8 shows the complete test setup.
Figure 8.
LED7706 board test setup
PWM Generator
DIM
GND
+
4.5V – 32V @ 2A
Power Supply
VINA-Meter
VIN+
ROW1
CH1
VBOOST
V-Meter
CH2
Scope
6x10 – 20mA WLEDs
Test Board
12/22
AN2809
9
Getting started
Getting started
The following step-by-step sequences are provided as a guideline to quickly evaluate the
performance of the LED7706 board.
9.1
Quick startup
Note:
Working in a ESD-protected environment is highly recommended. First check all wrist straps
and mat earth connections before handling the LED7706 board.
1.
Connect the power supply to the LED7706 board and insert the A-meter as shown in
Figure 8. Connect a V-meter between VBOOST and ground to monitor the output
voltage.
2.
Connect the proper WLEDs array to the J8 connector or to the row1-row6 and
VBOOST terminals of the LED7706 board.
3.
Set the PWM signal (20 kHz, 5% duty-cycle, 3.3 V CMOS logic levels) on a signal
generator and provide it to the DIM input.
4.
Set SW1 and SW2 to the lower position (fixed frequency and MODE to AVCC). Do not
change jumper settings when the board is switched on.
5.
Set the input voltage to 12 V.
6.
Turn on the PWM generator.
7.
Turn on the VIN supply: the device turns on.
8.
Vary the input voltage in the range 4.5–32 V.
9.
Set the input voltage to 12 V.
10. Vary the dimming duty-cycle from 1 to 100%.
11. Check the shape of the rows’ current at a 1% dimming duty-cycle.
Note:
When measuring the current of row x, an auto-ranging A-meter can trigger the open-row or
shorted-LED fault detection during the automatic scale selection procedure. Disabling the
auto-ranging option on the A-meter is recommended.
13/22
Getting started
9.2
AN2809
Open and shorted WLED fault testing
1.
Set the input voltage to 12 V.
2.
Set the dimming duty-cycle to 20%.
3.
Disconnect the rows in sequence and compare the behavior of the LED7706 to
Table 4.
4.
Restore all row connections and force the EN input to ground.
5.
Release the EN input.
6.
Short one or more WLEDs and compare the behavior of the LED7706 to Table 4.
7.
Press the SW3 push button of the LED7706 board to reset the device.
8.
Turn off the power supply and set the SW2 selector to the upper position (MODE to
ground).
9.
Turn on the power supply and repeat steps 3 to 7.
10. Remove all shorted WLEDs and leave ROW1 and ROW2 floating.
11. Turn on the power supply: the floating rows are ignored.
12. Turn off the PWM generator.
13. Turn off the power supply.
9.3
Device synchronization
1.
Set the PWM dimming signal to 100%.
2.
Remove the jumper from the SW1 selector to leave the FSW pin floating.
3.
Connect an external 600 kHz clock generator (0 to 1 V logic levels, 40% duty-cycle)
between the FSW test point and ground. Refer to Figure 9.
4.
Turn on the PWM generator.
5.
Turn on the power supply: the device remains off until the FSW pin is low.
6.
Turn on the clock generator: the device turns on.
7.
Monitor the SYNC output and verify the synchronization (the SYNC output is a replica
of the FSW signal).
8.
Turn off the PWM generator.
9.
Turn off the clock generator.
10. Turn off the power supply.
14/22
AN2809
Getting started
Figure 9.
LED7706 synchronization setup
600kHz – 40%
Clock Generator
PWM Generator
GND
FSW
SYNC
DIM
VIN4.5V – 32V @ 2A
Power Supply
VIN+
+
VBOOST
CH1
CH2
6x10 – 20mA WLEDs
Test Board
Scope
9.4
Efficiency measurements
Figure 10 shows the set-up used to perform efficiency measurements. The efficiency in this
device is typically defined as the ratio between the power provided to the load (current
flowing through the LEDs multiplied by the voltage across the LEDs) and the total input
power. The power dissipated in the current generators is correctly considered as a power
loss. This method of calculating the efficiency implies that the voltage across the LEDs is the
same for all the strings. However, this is not true. The power delivered to the load should be
calculated as follows.
6
P LOAD =
∑ VSTRINGi ⋅
I STRINGi
i=1
where VSTRING_i is the voltage across the LEDs in row i, whereas ISTRING_i is the current
flowing through row i. In order to ease the measurement, the voltage drop of all the
generators is equalized by connecting them together.
15/22
Getting started
AN2809
In this condition, the power provided to the LEDs is simply calculated as:
P LOAD = V STRING ⋅ I STRING
where VSTRING is the voltage across the parallelized channels, whereas ISTRING is the total
current delivered to the load (the sum of the current of the six channels). Since all the
channels are in parallel (120 mA total current), a single string of 150 mA-rated LEDs is
required as load (Figure 10).
Figure 10. Efficiency measurement setup
PWM Generator
DIM
GND
+
4.5V – 32V @ 2A
Power Supply
VINA-Meter
VIN+
ROW1
VBOOST
V-Meter
V-Meter
A-Meter
10 WLEDs 150mA array
Figure 11 and Figure 12 show two efficiency measurements against the duty-cycle of the
dimming signal at two different input voltages.
16/22
AN2809
Getting started
Figure 11. Efficiency vs DIM duty-cycle, Figure 12. Efficiency vs DIM duty-cycle,
VIN = 12 V, 10 white LEDs in
VIN = 24 V, 10 white LEDs in
series, IOUT = 120 mA
series, IOUT = 120 mA
17/22
WLEDs test board
10
AN2809
WLEDs test board
The WLEDs test board here described mounts sixty vertical white LEDs (size 0603, 20 mA)
arranged in a 6 x 10 matrix. Figure 13 shows an image of the board, whereas Figure 14
provides the schematic which can be used as reference to realize a customized board.
Several jumpers, switches and test points are provided to cover most of the test
configurations.
Figure 13. WLEDs test board
18/22
2
2
2
2
2
1
1
1
1
1
D10
J19
D20
J23
D30
J27
D40
J31
D50
J35
D60
2 1
2 1
2 1
2 1
2 1
2 1
TP10
J10
J11
J12
J13
J14
2
1
J38
D9
J18
D19
J22
D29
J26
D39
J30
D49
J34
D59
TP9
1
2 1
2 1
2 1
2 1
2 1
2 1
1
1
TP21
1
1
1
1
1
1
J15
J39
TP19
TP20
1
J9
1
2
1
D8
J17
D18
J21
D28
J25
D38
J29
D48
J33
D58
J37
2 1
2 1
2 1
2 1
2 1
2 1
TP8
1
1
TP18
D7
J16
D17
J20
D27
J24
D37
J28
D47
J32
D57
J36
2
2
2
2
2
2
TP7
1
1
TP17
D6
D16
D26
D36
D46
D56
TP6
1
D5
D15
D25
D35
TP5
1
D4
D14
D24
D34
D44
TP4
1
1
D45
TP14
1
D54
TP15
1
D55
TP16
J1
D3
D13
D23
D33
D43
D53
J2
3
2
1
TP3
1
1
TP13
1
2
3
D2
D12
D22
D32
D42
D52
TP2
1
1
D1
D11
D21
D31
D41
D51
TP12
TP1
1
1
TP11
J3
J4
J5
J6
J7
1
2
1
2
1
2
1
2
1
2
SW1
SW2
SW DIP-6
SW3
J8
HEADER 8X2
8
7
6
5
4
3
2
1
AM00673v1
9
10
11
12
13
14
15
16
AN2809
WLEDs test board
Figure 14. WLEDs test board schematic
19/22
WLEDs test board
AN2809
Table 5, Table 6 and Table 7 respectively describe the board’s jumper functions, switches
and test-points.
Table 5.
Test board jumper functions
Jumper
Function
Default position
J1
Two-position selector. Used in conjunction with SW1 to simulate
a fault on shorted LEDs on row1. When set to position 1, the D10
LED can be shorted by pressing SW1. When set to position 2,
both D9 and D10 LEDs can be shorted by pressing SW1.
1
J2
Two-position selector. Same function as J1 but related to row6
(D59 and D60 LEDs).
1
PCB tin-drop jumpers, bottom-sided. Used to parallelize the
desired number of rows.
J3 to J7
J8
8-terminal connector. Used to interface the LED7706
demonstration board.
J9
PCB tin-drop jumper, bottom-sided. Used to provide the output
voltage of the boost section of LED7706 to the low-current (D1D60), top-sided WLEDs array.
Shorted
J10 to J15
Two-pin jumpers, top-sided. Used to access the LED strings to
perform row current monitoring and voltage threshold
measurement.
Shorted
J16 to J39
PCB tin-drop jumper, bottom-sided. Used to reduce the number
of active LEDs of each row by shorting unused diodes.
Open
Table 6.
-
Test board switch functions
Switch
Function
Default position
SW1
Used in conjunction with J1 to simulate a shorted LED fault
condition. See J1 function.
Open (released)
SW2
Used in conjunction with J2 to simulate a shorted LED fault
condition. See J2 function.
Open (released)
SW3
DIP switch. Used to individually break ROW1 through row6.
Used to simulate open LED fault or unused (floating) rows.
ON
Table 7.
Test board test-point functions
Test point
Function
TP1 to TP10
PCB test points, top-sided. Used to easily access each LED of ROW1 (D1-D10).
TP11 to TP20
PCB test points, top-sided. Used to easily access each LED of ROW6 (D51-D60).
TP21
20/22
Open
PCB test point, top-sided. Auxiliary access to the output voltage.
AN2809
11
Revision history
Revision history
Table 8.
Document revision history
Date
Revision
Changes
10-Jan-2009
1
Initial release.
11-Feb-2009
2
Updated Table 2: LED7706 component list and Table 4: Fault
management summary
21/22
AN2809
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