LX1972-1995 EVAL KIT USER GUIDE
Microsemi
Integrated Products
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 1
Copyright © 2004
Rev. 1.0a, 2005-01-27
PDA SMART PHONE
LED POWER MANAGEMENT
EVALUATION BOARD
LX1972 & LX1995
TM ®
LX1972-1995 EVAL KIT USER GUIDE
Microsemi
Integrated Products
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 2
Copyright © 2004
Rev. 1.0a, 2005-01-27
T
ABLE OF
C
ONTENTS
Introduction............................................................................................................................................
3
Part Ordering Information ...................................................................................................................................... 4
Schematic ..............................................................................................................................................................5
Pin Definitions, Test Points, Hook Up.................................................................................................................... 6
Silkscreen............................................................................................................................................................... 7
Characteristic Curves............................................................................................................................................. 8
Bill of Materials..................................................................................................................................................... 10
LX1972-1995 EVAL KIT USER GUIDE
Microsemi
Integrated Products
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 3
Copyright © 2004
Rev. 1.0a, 2005-01-27
I
NTRODUCING TO
P
RODUCT
This evaluation board demonstrates several LED power management evaluation circuits. The LX1995 LED
driver IC is used in conjunction with the LX1972 Light Sensor to provide a LCD backlight that is variable with
ambient light. The backlight sensitivity to ambient light can be adjusted using the PWM input signal [PWM]. The
effect of the light sensor can be removed by changing the logic state of the [AUTO] signal. With AUTO in a logic
low state, the LCD backlight is variable with the PWM input, but the effect of the light sensor is disabled.
The evaluation board also provides the capability to provide power to a camera flash LED. During the period
when the flash is enabled, the LCD backlight is off, however, this may not be an issue since the shutter speed is
relatively fast when the image is being captured. The flash LED can be a single Luxeon type LED (as shown) or
could alternatively be several medium power high brightness LEDs wired in series (this option must be added on by
the evaluation board user).
The evaluation board (in AUTO mode) also provides a means to sense when there is sufficient ambient light to
view the keyboard so that the keyboard LEDs can be held off when the KEYBOARD ENABLE signal is high to
conserve power. This effect is overridden if AUTO is a logic low. In total darkness, the Keyboard LEDs will
illuminate when the KEYBOARD ENABLE signal is high, regardless of the state of the AUTO logic signal.
This evaluation board contains several discrete logic gates that may be implemented in programmable logic in the
final product. Without the discrete logic devices, the circuitry needed to implement these functions is quite small in
size.
The LX1995-2 is well suited for this application, because it is capable of driving loads up to 1.25 watts from a
lithium ion battery. The fixed feedback voltage node of the LX1995 is suitable for switching between feedback
from two different current sense resistors. If more power is necessary, consult Microsemi for higher power
LX1995 versions.
K
EY
F
EATURES
LX1972 LX1995
Near Human Eye Spectral Re sponse
Very Low IR Sensitivity
Highly Accurate & Repeatable Output Curre nt vs.
Light
Scalable Output Voltage
Temperature Stable
Integrated High Gain Photo Current Amplifiers
No Optical Filters Needed
< 1µA Shutdown Current
> 85% Maximum Efficiency
Efficient at Low Current Levels
< 70µA Quiescent Suppl y Cur rent in Operating Mode
V
IN
Range 1.6V to 5.5V
Logic Controlled Shutdown
Dimming Options: PWM or Varying DC Voltage
Tiny 5-Pin TSOT Package
Smallest External Components
A
PPLICATIONS
LX1972 LX1995
Portable Electronic Displa ys
LCD TV Backlight Systems
Digital Still Cameras (DSC)
Desk top Monitors
Notebook Computers
Pagers
Wireless Phones
PDAs
LED Driver
Digital Camera Displays
GPS Receivers
LX1972-1995 EVAL KIT USER GUIDE
Microsemi
Integrated Products
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 4
Copyright © 2004
Rev. 1.0a, 2005-01-27
P
ART
S
PECIFIC
I
NFORMATION
Part Number Product
Description
LX1972IBC Ambient Light Detector In 1206 package.
LX1995-1CSG Miniature LED Driver 325mA Switch Current in 5-Pin TSOT package
LX1995-2CSG Miniature LED Driver 500mA Switch Current in 5-Pin TSOT package
LX1995-1CSE Miniature LED Driver 325mA Switch Current in 5-Pin SOT-23 package
LX1995-2CSE Miniature LED Driver 325mA Switch Current in 5-Pin SOT-23 package
T
ABLE
1
–
P
ART
I
NFORMATION
EVALUATION BOARDS
LX1972-1995 EVAL KIT LX1995 LED driver using LX1972 Light Sensor.
T
ABLE
2
–
E
VALUATION
B
OARD
I
NFORMATION
LX1972-1995 EVAL KIT USER GUIDE
Microsemi
Integrated Products
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 5
Copyright © 2004
Rev. 1.0a, 2005-01-27
S
CHEMATIC
F
OR
LX1972-1995
SGE#3532
X1
PDA/SMART PHONE LIGHT MANAGEMENT
B
11Friday, May 07, 2004
Title
Size Document Number Rev
Date: Sheet of
KYPDLED3
WHITE
L1
10uH
LED4
WHITE
R14
200
C9
0.1uF
C8
0.1uF
LED1
WHITE
VIN
1
R4
10K
R11
1.5K
Q3-2
MBT3946DW
KEYPAD_ ENABLE
1
C6
0.1uF
R7
60.4K
Q1A
FDG6303N
2
Q1B
FDG6303N
5
GND
1
D1
UPS5817
R14
2.0K
R12
1M
U5B
SN74LVC2G08
6
53
84
KYPDLED2
WHITE
U6B
74LVC2G32
6
53
84
D2
BAT54CW
23
1
LS1
LX1972
VSS
2VDD 1
C7
0.1uF
R2
15.0
Q2
2SK3539
R15
3.3
U1
LX1995
FB 3
VIN
5
GND
2
/SHDN
4
SW 1
R8
49.9K
FLASH
1
U7B
SN74LVC2G02
5
63
84
D3
FLASH
AUTO
1
R13
442.0K
C4
10uF
LED2
WHITE
C1
4.7uF
R9
10K
3.3V
1
U5A
SN74LVC2G08
1
27
84
U6A
74LVC2G32
1
27
84
R1
100K
U7A
SN74LVC2G02
1
27
84
C2
1uF
PWM_ADJ
1
R3
5.76K
R5
44.2K
U4
S-89220ACNC-1C1-TF
1
34
52
-
+
U3B
SN74LVC2G04
3 4
147
R16
1
LED3
WHITE
C10
0.1uF
KPDLED1
WHITE
R6
19.1K
/SHDN
1
U3A
SN74LVC2G04
1 6
52
R10
4.99K
C5
0.1uF
C3
0.1uF
Q3-1
MBT3946DW
3.3V
3.3V
3.3V
3.3V
3.3V
MICROSEMI INTEGRATED PRODUCTS
SPARE
SPARE
Main
DIMMING
FLASH
KEYPAD
ILLUMINATION
CONTROL
LIGHT SENSOR
DIMMING
BACKLIGHT
FLASH
KEYPAD
AUTO
PWM
Figure 1 – LX1972-1995 EVAL KIT Schematic
LX1972-1995 EVAL KIT USER GUIDE
Microsemi
Integrated Products
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 6
Copyright © 2004
Rev. 1.0a, 2005-01-27
P1
PIN
D
EFINITIONS
:
(R
EFER TO
FIG.1)
PIN1-3 GND Negative power terminals or can be
used to GND scope prob es.
PIN4 KEYPAD_EN Has PULL UP resistor. Tie logic level
LO to disable keypa d LED’s
PIN5 3.3V Positive 3.3V power terminal LOGI C
gates
PIN6 Auto Pull Logic level HI to enable Light
sensor dimming. Tie to Logic level
LO. For PWM dimming only.
PIN7 PWM Apply 10Khz , 3.3V dimming signal
and vary duty cycle to adjust level
PIN8 V
IN
Positive power terminal for LED
Driver
PIN9 /SHDN Pull logic LO to disable the WHIT E
LED driver
PIN10 FLASH Pull logic HI to enable Flash
LED(D3)
T
EST
P
OINT
D
EFINITIONS
:
(R
EFER TO
FIG.1)
FB Feedb ack pin of the LED driver
V
IN
Positive power terminal to the LED driver
V
OUT
Output voltage of the LED driver
TP1 VSS pin of the LX1972 light sensor
TP2 VDD pin of the LX1972 light sensor
TP3 Collector of the PNP transistor of package Q3
TP4 Measure Flash LED current. Tied to R16(1
ohm). Divide voltage by 1.
TP5 Measure the current in the Backlight LED’s.
Take voltage and divide by 15
LX1972-1995
EVAL
KIT
H
OOK
U
P
Example 1: PWM Backlight Dimming
1. Apply +3.7V between V
IN
and GND
2. Tie Auto pin LO
3. Apply +3.3V between 3.3V and GND
4. Connect Pulse generator between PWM and
GND
5. Vary duty cycle and monitor TP5 voltage and
convert to current by
Dividing voltage by 15.
Example 2: PWM Backlight AUTO Dimming
1. Apply +3.7V between V
IN
and GND
2. Tie Auto pin HI
3. Apply +3.3V between 3.3V and GND
4. Connect Pulse generator between PWM and
GND.
5. Set duty cycle.
6. Using a calibrated light source and po sition over
the light sensor aperture. Then vary the ambient
light.
7. Monitor TP5 and convert to current by dividing by
15.
Example 3: Flash
1. Apply +3.7V between V
IN
and GND
2. Apply +3.3V between 3.3V and GND
3. Connect P1 Flash pin to +#.3V by jumper
4. Measure current by monitoring TP4 and dividing
voltage by 1.
Example 4: Keypad Light Sensor Control
1. Apply +3.7V between V
IN
and GND
2. Apply +3.3V between 3.3V and GND
3. Let KEYPAD_EN float
4. Tie Auto HI
5. Tie PWM HI
6. Cover light Sensor aperture and see keyboard
LED’s come on.
LX1972-1995 EVAL KIT USER GUIDE
Microsemi
Integrated Products
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 7
Copyright © 2004
Rev. 1.0a, 2005-01-27
LX1972-1995
P
RINTED
C
IRCUIT
B
OARD
L
AYOUT
U4
C4
C8
L1
P1
C6
LED1
U1
GND
U5
PWM
FLASH
D3
U6
R17
GND
C10
/SHDN
KPDLED1
GND
C1
R15
U7
C
C7
KYPDLED3
AUTO
LED2
D1
KEYPAD_EN
3.3V
C9
C5
KYPDLED2
C3
LS1
D2
VIN
Q1
C2
FLASH LED3
U3
R16
LED4
Q2
Q3
R3
R1
R2
R4
R14
R13 R12
R11
R10 R9
R8
R7
R6 R5
3000
3000
0
0
INTEGRATED PRODUCTS
BOOST CIRCUIT
SGE#3532 X2
DIMMING
KEYBOARD
ILLUMINATION
CONTROL
BACKLIGHT
LX1972 LIGHT SENSOR
KEYBOARD
LX1995
GND
SILKSCREEN TOP RR
R19
R18
GND
GND
GND
VIN
TP1
TP2
TP3
FB
TP5
TP4
VOUT
Microsemi
Figure 2 – Top Side LX1972-1995 EVAL KIT silk screen
LX1972-1995 EVAL KIT USER GUIDE
Microsemi
Integrated Products
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 8
Copyright © 2004
Rev. 1.0a, 2005-01-27
LX1972-1995
C
HARACTERISTIC
C
URVES
0
5
10
15
20
25
30
0 20406080100
Duty Cycle (%)
Backlight Current (mA)
Duty Cycle Vs
LED Current
Figure 3 – Duty Cycle versus LED Current
0
5
10
15
20
25
30
0 200 400 600 800 1000
Ambient (L ux)
Led Backlight Current
20% 40% 60%
80% 99.90%
Figure 4 – Ambient Light
0
100
200
300
400
500
3456
V
IN
(V)
Iflash (mA)
Iflash(mA)
Figure 5 – VIN versus I flash
LX1972-1995 EVAL KIT USER GUIDE
Microsemi
Integrated Products
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 9
Copyright © 2004
Rev. 1.0a, 2005-01-27
Dimming Mode
Duty Cycle (%) VSNS(mV) ISNS (mA)
1 26 1.733
10 58 3.968
20 93 6.2
30 128 8.533
40 163 10.867
50 194 12.933
60 233 15.533
70 268 17.867
80 302 20.133
90 337 22.467
99.9 373 24.867
PDA / Smart Phone Evaluation PCB Dimming Data
PDA Smart Phone Flash Regulation
V
IN
(V) I flash (mA)
3.0 242
3.2 269
3.4 295
3.6 318
3.8 317
4.0 314
4.2 324
4.4 338
4.6 353
4.8 369
5.0 389
5.1 397
5.2 403
5.3 408
5.4 381‡
5.5 397
‡ LX1995 Stops switching at this point
PWM Dimming Auto Mode
DC 20% DC 40% DC 60% DC 80% DC 99.9%
Amb
(LUX) V
SN
(mV) I
SNS
(mA) V
SN
(mV) I
SNS
(mA) V
SN
(m
V) I
SNS
(mA) V
SN
(mV) I
SNS
(mA) V
SN
(mV) I
SNS
(mA)
1 77.3 5.153 77.6 5.173 77.8 5.187 78.2 5.213 79 5.2.67
50 85 5.667 93 6.2 101 6.733 109 7.267 117 7.8
100 93 6.2 108 7.2 124 8.267 139 9.267 155 10.333
150 100 6.667 123 8.2 146 9.733 169 11.267 193 12.867
200 108 7.2 139 9.267 171 11.4 204 13.6 235 15.667
250 114 7.6 152 10.133 190 12.667 228 15.2 268 17.867
300 120 8 163 10.867 208 13.867 253 16.867 296 19.733
350 124 8.267 173 11.533 221 14.733 272 18.133 318 21.2
400 128 8.533 180 12 232 15.467 283 18.867 335 22.333
500 132 8.8 188 12.533 245 16.333 300 20 352 23.467
600 134 8.933 192 12.8 251 16.733 307 20.467 361 24.067
700 135 9 193 12.867 252 16.8 310 20.667 367 24.467
800 135 9 194 12.933 255 17 312 20.8 370 24.667
900 135 9 195 13 256 17.067 313 20.867 371 24.733
1000 135 9 195 13 256 17.067 314 20.933 372 24.8
LX1972-1995 EVAL KIT USER GUIDE
Microsemi
Integrated Products
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 10
Copyright © 2004
Rev. 1.0a, 2005-01-27
LX1972-1995
B
ILL OF
M
ATERIALS
MISCELLANEOUS COMPONENTS
Line
Item Part Description Manufacturer & Part # Case Reference
Designators Qty
1 Mini White LED Driver
M
ICROSEMI
LX1995-1SC TSOT U1 1
2 Visible Light Sensor
M
ICROSEMI
LX1972 1206 LS1 1
3 Schottky Diode: 1A, 20V
M
ICROSEMI
UPS5817 PWR D1 1
4 LED: White
M
ICROSEMI
UPLED
KPDLED1,
KYPDLED2,
KYPDLED3, LED1,
LED2, LED3, LED4
7
5 Dual Schottky Diode: 30V, 200mA
D
IODES
I
NC
BAT54CW SOT23 D2 1
6 LED, SMT White: Flash
LUXEON
D3 1
7 Inductor 47µF, Low Profile Power Wafer
C
OIL
C
RAFT
LPO3310-473MX L1 1
8 MOSFET N-Channel
P
ANASONIC
2SK3539 SMINI Q2 1
9 FET Dual N-Channel
F
AIRCHILD
FDG6303N SC70 Q1 1
10 Dual Transistor NPN & PNP
ON
S
EMI
MBT3946DW1T1
SOT363 Q3 1
11 Test Point White Loop
K
EY
S
TONE
5007 GND 4
12 IC CMOS Single Comparator 10µA
S
EIKO
I
NST
.
S-89220ACNC-1C1-TR SC70 U4 1
13 IC Dual Inverter
TI
SN74LVC2G04DCKR
SC70 U3 1
14 IC Dual 2 Input AND Gate
TI
SN74LBC2G08DCTR MSOP U5 1
15 IC Dual 2 Input OR Gate
TI
SN74LVC2G32DCTR
MSOP U6 1
16 IC Dual 2 Input NOR Gate
TI
SN74LVC2G02DCTR MSOP U7 1
17 10 Pin .100 Straight Header P1 1
CAPACITORS
Line
Item Part Description Part Description Case Reference
Designators Qty
1 Capacitor, X5R, 6.3V, 4.7µF, 10%
T
AIYO
Y
UDEN
JMK212BJ475KG 0805 C1, C2 2
2 Capacitor, X7R, 16V, 0.1µF, 10%
P
ANASONIC
ECJ1VB1C104K 0603 C3, C5, C6, C7,
C8, C9, C10 7
3 Capacitor, X5R, 20%, 10µF, 20%
T
AIYO
Y
UDEN
EMK325BJ106MN 1210 C4 1
RESISTORS
Line
Item Part Description Part Description Case Reference
Designators Qty
1 Resistor, 100K, 5%, 1/10W
R
OHM
MCRO3EZPJ104 0603 R1 1
2 Resistor, 15Ohm, 1%, 1/10W
R
OHM
MCRO3EZPF15R0
0603 R2 1
3 Resistor, 5.76K, 1%, 1/10W
R
OHM
MCRO3EZPJ5761 0603 R3 1
4 Resistor, 10K, 5%, 1/10W
R
OHM
MCRO3EZPJ103 0603 R4, R9 2
5 Resistor, 44.2K, 1%, 1/10W
R
OHM
MCRO3EZPJ4422 0603 R5 1
6 Resistor, 19.1K, 1%, 1/10W
R
OHM
MCRO3EZPF1912
0603 R6 1
7 Resistor 60.4K, 1%, 1/10W
R
OHM
MCRO3EZPF6042
0603 R7 1
8 Resistor, 49.9K, 1%, 1/10W
R
OHM
MCRO3EZPF4992
0603 R8 1
9 Resistor, 4.99K, 1%, 1/10W
R
OHM
MCRO3EZPF4991
0603 R10 1
10 Resistor, 1.5K, 5%, 1/10W
R
OHM
MCRO3EZPJ152 0603 R11 1
11 Resistor, 1M, 5%, 1/10W
R
OHM
MCRO3EZPJ105 0603 R12 1
12 Resistor, 442K, 1%, 1/10W
R
OHM
MCRO3EZPF4423
0603 R13 1
13 Resistor 2K, 1%, 1/10W
R
OHM
MCRO3EZPF2001
0603 R14 1
14 Resistor, 3.3Ohm, 5%, 1/2W
P
ANASONIC
ERJ-12ZYJ3R3U 2010 R15 1
15 Resistor, 1Ohm, 5%, 1/4W
P
ANASONIC
ERJ-8RQJ1R0V 1206 R16 1
16 Resistor, 200Ohm, 5%, 1/2W
P
ANASONIC
ERJ-12ZYJ201U 2010 R17 1
LX1972 Protected by U.S. Patents: 6,787,757: Patents Pending
