LX1992EVALKIT [ETC]
LED Driver ; LED驱动器\n
| 型号： | LX1992EVALKIT |
| 厂家： | 
ETC |
| 描述： | LED Driver
|
| 文件： | 总11页 (文件大小：346K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LX1992
High Efficiency LED Driver
L I N F I N I T Y D I V I S I O N
PRODUCTION
KEY FEATURES
DESCRIPTION
ꢀ > 90% Efficiency
The LX1992 is a compact high
Programming the output current is
ꢀ 80µA Typical Quiescent Supply
Current
efficiency step-up boost controller for readily achieved by using one external
driving white or color LEDs in current sense resistor in series with the
backlight or frontlight systems and LEDs. In this configuration, LED
offers designers maximum flexibility current provides a feedback signal to
with respect to efficiency and cost. the FB pin, maintaining constant current
ꢀ Externally Programmable Peak
Inductor Current Limit For
Maximum Efficiency
ꢀ Logic Controlled Shutdown
ꢀ < 1µA Shutdown Current
ꢀ Dynamic Output Current
Adjustment Via Analog
Reference Or Direct PWM Input
ꢀ 8-Pin MSOP Package or 8-Pin
MLP
The LX1992 features
a pseudo- regardless of varying LED forward
hysteretic pulse frequency modulation voltage (VF). Moreover, the LX1992 is
topology and uses an external N- capable of achieving output currents in
Channel MOSFET.
Further, the excess of 150mA, depending on the
LX1992 features control circuitry that MOSFET selected.
is optimized for portable systems (e.g.,
The LX1992 has an additional feature
quiescent supply current of 80µA for simple dynamic adjustment of the
(typ) and a shutdown current of less output current (i.e., up to 100% of the
APPLICATIONS/BENEFITS
than
1µA).
These
design maximum
programmed
current).
ꢀ Pagers
enhancements provide for improved Designers can make this adjustment via
performance in battery operated an analog reference signal or a direct
ꢀ Wireless Phones
ꢀ PDAs
systems applications.
PWM generated signal applied to the
ꢀ Handheld Computers
ꢀ General LCD Bias Applications
ꢀ LED Driver
The device input voltage range is ADJ pin and any PWM amplitude is
from 1.6V to 6.0, allowing for a wide easily accommodated with a single
selection of system battery voltages external resistor.
ꢀ Digital Camera Displays
and
start-up
operation
is
The LX1992 is available in both the 8-
Pin MSOP, and the miniature 8-Pin MLP
requiring minimal PCB area.
guaranteed at 1.6V input.
IMPORTANT: For the most current data, consult MICROSEMI’s website: http://www.microsemi.com
PRODUCT HIGHLIGHT
L1
VBAT = 1.6V to 6.0V
47µH
1206 Case Size
C1
4.7µF
DRV
IN
SRC
SHDN
ON OFF
LX1992
FB
ADJ
CS
GND
RCS
4kΩ
VF = 3.6V typ.
ILED = 20mA to 0mA
RSET
15Ω
PACKAGE ORDER INFO
Plastic MLP
8-Pin
LX1992CLM
Plastic MSOP
DU
8-Pin
TA (°C)
0 to 70
LM
LX1992CDU
Note: Available in Tape & Reel.
Append the letter “T” to the part number. (i.e. LX1992CDUT)
Copyright 2000
Microsemi
Page 1
Rev. 1.1, 2002-11-21
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
LX1992
High Efficiency LED Driver
L I N F I N I T Y D I V I S I O N
PRODUCTION
ABSOLUTE MAXIMUM RATINGS
PACKAGE PIN OUT
Supply Voltage (VIN) ....................................................................... -0.3V to 7.0V
Feedback Input Voltage (VFB).................................................-0.3V to VIN + 0.3V
Shutdown Input Voltage (VSHDN) ...........................................-0.3V to VIN + 0.3V
Analog Adjust Input Voltage (VADJ).......................................-0.3V to VIN + 0.3V
Source Input Current (ISRC).................................................................... 0.80 ARMS
Operating Junction Temperature.................................................................. 150°C
Storage Temperature Range...........................................................-65°C to 150°C
Lead Temperature (Soldering 180 seconds)................................................. 235°C
1
2
3
4
8
7
6
5
SRC
GND
CS
DRV
IN
FB
SHDN
ADJ
DU PACKAGE
(Top View)
Note: Exceeding these ratings could cause damage to the device. All voltages are with respect to
Ground. Currents are positive into, negative out of specified terminal.
SRC
GND
CS
1
2
3
4
8
7
6
5
DRV
IN
FB
THERMAL DATA
ADJ
SHDN
LM PACKAGE
(Top View)
Plastic MSOP 8-Pin
DU
THERMAL RESISTANCE-JUNCTION TO AMBIENT, θJA
THERMAL RESISTANCE-JUNCTION TO CASE, θJC
206°C/W
39°C/W
Plastic MLP 8-Pin
LM
THERMAL RESISTANCE-JUNCTION TO AMBIENT, θJA
41°C/W
5.2°C/W
THERMAL RESISTANCE-JUNCTION TO CASE, θJC
Junction Temperature Calculation: T = T + (P x θ ).
JC
J
A
D
The θJA numbers are guidelines for the thermal performance of the device/pc-board
system. All of the above assume no ambient airflow.
FUNCTIONAL PIN DESCRIPTION
NAME
DESCRIPTION
Unregulated IC Supply Voltage Input – Input range from +1.6V to 6.0V. Bypass with a 1µF or greater capacitor
IN
for operation below 2.0V.
Feedback Input – Connects to a current sense resistor between the output load and GND to set the output
FB
current.
Active-Low Shutdown Input – A logic low shuts down the device and reduces the supply current to 0.2µA (Typ).
SHDN
Connect
to VCC for normal operation.
SHDN
DRV
CS
GND
MOSFET Gate Driver – Connects to an external N-Channel MOSFET.
Current-Sense Amplifier Input – Connecting a resistor between CS and GND sets the peak inductor current limit.
Common terminal for ground reference.
Adjustment Signal Input – Provides the internal reference, via an internal filter and gain resistor, allowing a
dynamic output current adjustment corresponding to a varying duty cycle. The actual ADJ pin voltage range is
ADJ
from VIN to GND. In order to minimize the current sense resistor power dissipation a practical range of VADJ
0.0V to 0.5V should be used.
=
SRC
MOSFET Current Sense Input - Connects to the External N-Channel MOSFET Source.
Note: ADJ pin should not be left floating.
Copyright 2000
Rev. 1.1, 2002-11-21
Microsemi
Page 2
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
LX1992
High Efficiency LED Driver
L I N F I N I T Y D I V I S I O N
PRODUCTION
ELECTRICAL CHARACTERISTICS
Unless otherwise specified, the following specifications apply over the operating ambient temperature 0°C ≤ TA ≤ 70°C except where
otherwise noted and the following test conditions: VIN = 3V, ILOAD = 20mA, = V and VADJ = 300mV.
SHDN
Test Conditions
IN
,
LX1992
Typ
Parameter
Symbol
Units
Min
Max
`
Operating Voltage
VIN
1.6
6.0
1.6
V
V
Minimum Start-up Voltage
VSU
TA = +25°C
Start-up Voltage Temperature
Coefficient
kVST
-2
mV/°C
VFB > 0.3V
VSHDN < 0.4V
50
0.2
300
100
0.5
325
100
VIN
0
µA
µA
mV
nA
V
Quiescent Current
IQ
FB Threshold Voltage
FB Input Bias Current
ADJ Input Voltage Range
ADJ Input Bias Current
VFB
IFB
275
-100
0.0
VFB = 0.3V
VADJ
IADJ
IOUT = (VADJ)/(RSET
VADJ < 0.3V
)
-150
-50
nA
nA
V
V
Shutdown Input Bias Current
ISHDN
50
= GND
SHDN
Shutdown High Input Voltage
Shutdown Low Input Voltage
Current Sense Bias Current
Minimum Peak Current
Efficiency
NDRV Sink Current
NDRV Source Current
Off-Time
VSHDN
VSHDN
1.6
0.4
7.0
83
ICS
IMIN
η
ISNK
ISRC
tOFF
VFB < 0.3V
CS = 560Ω
3.0
53
5.0
µA
mA
%
R
VIN = 3.0V, ILOAD = 20mA
VIN = 5V
85
50
mA
mA
ns
VIN = 5V
100
VFB = 0.3V; VADJ=0.5V
100
500
SIMPLIFIED BLOCK DIAGRAM
FB
A
DRV
SRC
GND
Reference
Logic
Control
Logic
Driver
ADJ
50pF
2.5MΩ
5µA
B
CS
Shutdown
Logic
IN
SHDN
Copyright 2000
Microsemi
Page 3
Rev. 1.1, 2002-11-21
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
LX1992
High Efficiency LED Driver
L I N F I N I T Y D I V I S I O N
PRODUCTION
APPLICATION CIRCUITS
Typical LED Driver Applications
L1
VBAT = 1.6V to 6.0V
47µH
1206 Case Size
C1
4.7µF
DRV
SRC
IN
SHDN
ON OFF
LX1992
FB
CS
ADJ
GND
RCS
4kΩ
VF = 3.6V typ.
ILED = 0mA to 20mA
RSET
15Ω
Figure 1 – LED Driver with Full-Range Dimming Via PWM Input
L1
VBAT = 1.6V to 6.0V
47µH
1206 Case Size
C1
4.7µF
DRV
IN
SRC
SHDN
ON OFF
LX1992
FB
CS
ADJ
+
-
GND
RCS
4kΩ
VADJ = 0.0V to 0.3V
RSET
15Ω
VF = 3.6V typ.
ILED = 0mA to 20mA
Figure 2 – LED Driver with Full-Range Dimming Via Analog Voltage Input
Note: The component values shown are only examples for a working system. Actual values will vary greatly depending on
desired parameters, efficiency, and layout constraints.
Copyright 2000
Rev. 1.1, 2002-11-21
Microsemi
Page 4
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
LX1992
High Efficiency LED Driver
L I N F I N I T Y D I V I S I O N
PRODUCTION
APPLICATION INFORMATION
OPERATING THEORY
INDUCTOR SELECTION AND OUTPUT CURRENT LIMIT
PROGRAMMING
The LX1992 is a PFM boost converter that is
optimized for driving a string of series connected LEDs. It
operates in a pseudo-hysteretic mode with a fixed switch
“off time” of 300ns. Converter switching is enabled as
LED current decreases causing the voltage across RSET to
decrease to a value less than the voltage at the VADJ pin.
When the voltage across RSET (i.e., VFB) is less than VADJ,
comparator A activates the control logic. The control logic
activates the DRV output circuit that connects to the gate
of the external FET. The DRV output is switched “on”
(and remains “on”) until the inductor current ramps up to
the peak current level. This current level is set via the
external RCS resistor and monitored through the CS and
SRC inputs by comparator B.
Setting the level of peak inductor current to approximately
2X the expected maximum DC input current will minimize
the inductor size, the input ripple current, and the output
ripple voltage. The designer is encouraged to use inductors
that will not saturate at the peak inductor current level. An
inductor value of 47µH is recommended. Choosing a lower
value emphasizes peak current overshoot while choosing a
higher value emphasizes output ripple voltage. The peak
switch current is defined using a resistor placed between the
CS terminal and ground and the IPEAK equation is:
V
I
CS
+
t +
R
IN
IPEAK = IMIN
D
CS
L
R
ICS
The LED load is powered from energy stored in the
output capacitor during the inductor charging cycle. Once
the peak inductor current value is achieved, the NDRV
output is turned off (off-time is typically 300ns) allowing a
portion of the energy stored in the inductor to be delivered
to the load (e.g., see Figure 5, channel 2). This causes the
output voltage to continue to rise across RSET at the input to
the feedback circuit. The LX1992 continues to switch until
the voltage at the FB pin exceeds the control voltage at the
ADJ pin.
The maximum IPEAK value is limited by the ISRC value
(max. = 0.8ARMS). The minimum IPEAK value is defined
when RCS is zero. The value range for parameters IMIN and
ICS
section of this data sheet. The parameter tD
are provided in the ELECTRICAL CHARiAsCrTeElRatIeSdTICtoS
internal operation of the device. A typical value at 25oC is
800ns. RICS is the internal current sense resistor connected to
the SRC pin. A typical value at 25oC is 200mΩ. All of these
parameters have an effect on the final IPEAK value.
DESIGN EXAMPLE:
Determine IPEAK where VIN equals 3.0V and RCS equals
4.02KΩ using nominal values for all other parameters.
The value of RSET is established by dividing the
maximum adjust voltage by the maximum series LED
current. A minimum value of 15Ω is recommended for
R
SET. The voltage at the FB pin is the product of IOUT (i.e.,
5.0µA
3.0V
IPEAK = 73mA+
×800ns+
×4.02KΩ
the current through the LED chain) and RSET
V
.
47µH
200mΩ
The result of this example yields a nominal IPEAK of
approximately 225mA.
ADJmaxI
RSET
=
LEDmax
The application of an external voltage source at the
ADJ pin provides for output current adjustment over the
entire dimming range and the designer can select one of
two possible methods. The first option is to connect a
PWM logic signal to the ADJ pin (e.g., see Figure 1). The
LX1992 includes an internal 50pF capacitor to ground that
works with an external resistor to create a low-pass filter
(i.e., filter out the AC component of a pulse width
modulated input of fPWM ≥ 100KHz). The second option is
to adjust the reference voltage directly at the ADJ pin by
applying a DC voltage from 0.0 to 0.3V (e.g., see Figure
2). The adjustment voltage level is selectable (with limited
accuracy) by implementing the voltage divider created
between the external series resistor and the internal 2.5MΩ
resistor. Disabling the LX1992 is achieved by driving the
SHDN pin with a low-level logic signal thus reducing the
device power consumption to less than 0.5µA (typ).
OUTPUT RIPPLE AND CAPACITOR SELECTION
Output voltage ripple is a function of the inductor value
(L), the output capacitor value (COUT), the peak switch
current setting (IPEAK), the load current (IOUT), the input
voltage (VIN) and the output voltage (VOUT) for a this boost
converter regulation scheme. When the switch is first turned
on, the peak-to-peak voltage ripple is a function of the
output droop (as the inductor current charges to IPEAK), the
feedback transition error (i.e., typically 10mV), and the
output overshoot (when the stored energy in the inductor is
delivered to the load at the end of the charging cycle).
Therefore the total ripple voltage is
V
RIPPLE = ∆VDROOP + ∆VOVERSHOOT + 10mV
The initial droop can be estimated as follows where the
0.5 value in the denominator is an estimate of the voltage
drop across the inductor and the FET’s RDS_ON: The
Copyright 2000
Rev. 1.1, 2002-11-21
Microsemi
Page 5
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
LX1992
High Efficiency LED Driver
L I N F I N I T Y D I V I S I O N
PRODUCTION
APPLICATION INFORMATION
PCB LAYOUT
formula for ∆VDROOP is:
The LX1992 produces high slew-rate voltage and current
waveforms hence; the designer should take this into
consideration when laying out the circuit. Minimizing trace
lengths from the IC to the inductor, transistor, diode, input
and output capacitors, and feedback connection (i.e., pin 6)
are typical considerations. Moreover, the designer should
maximize the DC input and output trace widths to
accommodate peak current levels associated with this
topology.
L
×
(
IPK × IOUT
)
= COUT
∆VDROOP
(
VIN − 0.5)
The output overshoot can be estimated as follows where the
0.5 value in the denominator is an estimate of the voltage
drop across the diode:
L
2
1
×
×
IPK − IOUT
( )
2
EVALUATION BOARD
COUT
∆VOVERSHOOT
DESIGN EXAMPLE:
Determine the VRIPPLE where IPK equals 200mA, IOUT
equals 12.8mA, L equals 47µH, COUT equals 4.7µF, VIN
equals 3.0V, and VOUT equals 13.0V:
=
The LXE1992 evaluation board is available from
Microsemi for assessing overall circuit performance. The
evaluation board, shown in Figure 3, is 3 by 3 inches (i.e.,
7.6 by 7.6cm) square and programmed to drive 4 LEDs
(provided). Designers can easily modify circuit parameters
to suit their particular application by replacing RCS (as
described in this section) RSET (i.e., R4) and diode load.
Moreover, the inductor, FET, and switching diode are easily
swapped out to promote design verification of a circuit that
maximizes efficiency and minimizes cost for a specific
(
VOUT + 0.5 − V
)
IN
47µH
4.7µF
×
200mA×12.8mA
( )
∆VDROOP
=
≅ 10.2mV
(
3.0 − 0.5)
application.
The evaluation board input and output
47µH
4.7µF
2
1
connections are described in Table 1.
×
2
×
(
200mA −12.8mA
)
The DC input voltage is applied to VBAT (not VCC)
however the LX1992 IC may be driven from a separate DC
source via the VCC input. The output current (i.e., LED
brightness) is controlled by adjusting the on-board
∆VOVERSHOOT
=
≅ 18.4mV
(
13.0 + 0.5 − 3.0)
Therefore, VRIPPLE = 10.2mV + 18.4mV + 10mV = 38.6mV
DIODE SELECTION
potentiometer.
The designer may elect to drive the
brightness adjustment circuit from VBAT or via a separate
voltage source by selecting the appropriate jumper position
(see Table 2). Optional external adjustment of the output
LED current is achieved by disengaging the potentiometer
and applying either a DC voltage or a PWM-type signal to
the VADJ input. The PWM signal frequency should be
higher than 150KHz and contain a DC component les than
350mV.
A Schottky diode is recommended for most applications
(e.g. Microsemi UPS5817). The low forward voltage drop
and fast recovery time associated with this device supports
the switching demands associated with this circuit
topology. The designer is encouraged to consider the
diode’s average and peak current ratings with respect to
the application’s output and peak inductor current
requirements. Further, the diode’s reverse breakdown
voltage characteristic must be capable of withstanding a
The LX1992 exhibits a low quiescent current (IQ < 0.5µA:
typ) during shutdown mode. The SHDN pin is used to
exercise the shutdown function on the evaluation board.
This pin is pulled-up to VCC via a 10KΩ resistor.
Grounding the SHDN pin shuts down the IC (not the circuit
output). The output voltage (i.e., voltage across the LED
string) is readily measured at the VOUT terminal and LED
current is derived from measuring the voltage at the VFDBK
pin and dividing this value by 15Ω (i.e., R4).
negative voltage transition that is greater than VOUT
.
TRANSISTOR SELECTION
The LX1992 can source up to 100mA of gate current.
An N-channel MOSFET with a relatively low threshold
voltage, low gate charge and low RDS(ON) is required to
optimize overall circuit performance. The LXE1992
Evaluation Board uses a Fairchild FDV303. This NMOS
device was chosen because it demonstrates an RDS_ON of
0.33Ω and a total gate charge Qg of 1.64nC (typ.)
The factory installed component list for this must-have
design tool is provided in Table 3 and the schematic is
shown in Figure 4
Copyright 2000
Rev. 1.1, 2002-11-21
Microsemi
Page 6
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
LX1992
High Efficiency LED Driver
L I N F I N I T Y D I V I S I O N
PRODUCTION
APPLICATION INFORMATION (CONTINUED)
Figure 5: LXE1992 Engineering Evaluation Board
Table 1: Input and Ouput Pin Assignments
Pin Name
Allowable Range
Description
VBAT
VCC
0 to 6V
Main power supply for output. (Set external current limit to 0.5A)
LX1992 power. May be strapped to VBAT or use a separate supply if VCC jumper is in
1.6V to 6V
the SEP position. Do not power output from VCC pin on board..
Potentiometer power. May be strapped to VBAT or use a separate supply if VPOT
jumper is in the SEP position. Do not power output from VPOT pin on board.
Apply a DC voltage or a PWM voltage to this pin to adjust the LED current. PWM
inputs should be greater than 120Hz and DC portion less than 350mV.
VPOT
1.6V to 6V
0 to 350mV
VADJ IN
/SHDN
VOUT
0 to VCC
0 to 18V
Pulled up to VCC on board (10KΩ), Ground to inhibit the LX1992.
Power supply output voltage that is applied to LED string.
VFDBK
0 to 400mv
Sense resistor voltage. Divide this voltage by 15 to determine LED current.
Table 2: Jumper Pin Position Assignments
Functional Description
Jumper Position
VCC/ BAT
Use this position when powering VBAT and VCC from the same supply. Do not connect power to the VCC
input when using this jumper position.
VCC/ SEP
Use this position when using a separate VCC supply (different from VBAT).
Use this position when powering the potentiometer reference circuit from the VBAT supply. Do not connect
power to the VCC input when using this jumper position.
VPOT/ VBAT
Use this position when using a separate power supply (different from VBAT) to power the potentiometer
reference circuit. This will lower the VBAT current and provide a more accurate efficiency reading for the
LX1992 circuit.
VPOT/ SEP
ADJ/ POT
ADJ/ EXT
Use this position when using the potentiometer to adjust LED current.
Use this position when adjusting the LED current with an external PWM that has a repetition rate >120Hz. Or
when using a DC adjustment voltage.
Note: Always put jumpers in one of the two possible positions
Copyright 2000
Rev. 1.1, 2002-11-21
Microsemi
Page 7
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
LX1992
High Efficiency LED Driver
L I N F I N I T Y D I V I S I O N
PRODUCTION
APPLICATION INFORMATION (CONTINUED)
Table 3: Factory Installed Component List for the LX1992 Evaluation Board
Part
Reference
Part
Number
Quantity
Description
Manufacturer
1
1
1
2
2
1
1
1
2
1
1
1
1
4
3
3
Q1
Mosfet, N-Channel, 25V, SOT23 Type SMT
Rectifier, Schottky, 1A, 20V, Powermite Type SMT
Inductor, 47uH, 540mA, SMT
Fairchild
Microsemi
Toko
FDV303N
CR1
UPS5817
L1
A920CY-470
C1, C2
C3, C4
R4
Capacitor, Ceramic X5R, 4.7uF, 25V, 1210 Type SMT
Capacitor, Ceramic X7R, 0.1uF, 50V, 0805 Type SMT
Resistor, 15 Ohm, 1/10W, 0805 Type SMT
Resistor, 1K, 1/16W, 0603 Type SMT
Resistor, 4.02K, 1/16W, 0603 Type SMT
Resistor, 100K, 1/16W, 0603 Type SMT
Resistor, 10K, 1/16W, 0603 Type SMT
Trimpot, 50K, 1/2W, Through Hole Type
IC, Voltage Reference, 1.25 Volts, SOT23 Type SMT
Diode, Zener, 24V, 3W Powermite Type SMT
White LED
Taiyo Yuden
Murata
CETMK325BJ475MN
GRM40X7R104M050
ERJ6ENF15R0
ERJ3EKF1001
ERJ3EKF4021
ERJ3EKF1003
ERJ3EKF1002
3352E-1-503
LX432CSC
Panasonic
Panasonic
Panasonic
Panasonic
Panasonic
Bourns
R5
R2
R3, R6
R1
R7
VR1
Microsemi
Microsemi
Chicago Miniature
3M
VR2
1PMT5934B
LED1 - 4
JB1 - JB3
CMD333UWC
929647-09-36
929955-06
Header, 3 Pos Vertical Type
Jumper
3M
Note: The minimum set of parts needed to build a working power supply are: Q1, CR1, L1, C2, C3, R2, R4, U1.
CR1
UPS5817
L1
47µH
VBAT
GND
C2
4.7µF
25V
C1
4.7µF
25V
VPOT
VCC
VOUT
Q1
FDV303N
CMD333UW C
CMD333UW C
C3
0.1µF
50V
SRC
NDRV
VR2
VCC
20V
GN
D
IN
FB
1W
1PMT4114
R1
10k
CS
R2
4.02k
ADJ
SHDN
CMD333UW C
CMD333UW C
SHDN
VADJ
R3
100k
VFDBK
R4
15Ω
VADJ
R5 1k
C4
0.1µF
25V
VPOT
R6
100k
VR1
LX432
R7
50k
Figure 4 – LXE1992 Boost Evaluation Board Schematic
Copyright 2000
Microsemi
Page 8
Rev. 1.1, 2002-11-21
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
LX1992
High Efficiency LED Driver
L I N F I N I T Y D I V I S I O N
PRODUCTION
CHARACTERISTIC CURVES
Figure 6: VOUT and Inductor Current Waveforms.
Channel 1: VOUT (AC coupled; 100mV/div)
Figure 5: VOUT and Inductor Current Waveforms.
Channel 1: VOUT (AC coupled; 200mV/div)
Channel 2: Inductor Current (100mA/div.)
Channel 2: Inductor Current (100mA/div.)
Configuration: VIN = 3.0V, VOUT = 13.7V, IIN = 120mA
Configuration: VIN = 3.0V, VOUT = 13.0V, IIN = 65mA
90%
80%
70%
60%
50%
5
4
3
2
1
0
0
20
40
60
80
100
120
140
160
0
2
4
6
8
10
12
14
16
18
Drive Current (mA)
LED Current (mA)
Figure 7: Gate Drive Voltage vs. Drive Current
at T = 25oC.
Figure 8: Efficiency vs. LED Output Current.
Configuration: VIN = 3.0V, L = 47µH, RCS = 4KΩ
Note: Data taken from LXE1992 Evaluation Board
100%
90%
80%
70%
60%
50%
Efficiency Measurement Hint: When doing an efficiency
evaluation using the LX1992 Evaluation Board, VPOT should
be driven by a separate voltage supply to account for losses
associated with the onboard reference (i.e., the 1.25V shunt
regulator and 1KΩ resistor). This circuit will have VBAT -
1.25V across it and at the higher input voltages the 1KΩ
resistor could have as much as 4mA through it. This shunt
regulator circuitry will adversely effect the overall efficiency
measurement and is not normally used in an application.
Therefore it should not be considered when measuring
efficiency.
0
2
4
6
8
10 12 14 16 18 20 22 24
LED Current (mA)
Figure 9: Efficiency vs. LED Output Current.
Configuration: VIN = 5.0V, L = 47µH, RCS = 4KΩ
Note: Data taken from LXE1992 Evaluation Board
Copyright 2000
Rev. 1.1, 2002-11-21
Microsemi
Page 9
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
LX1992
High Efficiency LED Driver
L I N F I N I T Y D I V I S I O N
PRODUCTION
PACKAGE DIMENSIONS
8-Pin Miniature Shrink Outline Package (MSOP)
DU
A
MILLIMETERS
INCHES
Dim
MIN
2.85
2.90
–
MAX
3.05
3.10
1.10
0.40
MIN
.112
.114
–
MAX
.120
A
B
C
.122
0.043
0.160
B
D
0.25
0.009
G
H
J
0.65 BSC
0.025 BSC
0.38
0.13
0.64
0.18
0.015
0.005
0.025
0.007
H
G
K
0.95 BSC
0.037 BSC
P
L
M
N
P
0.40
0.70
0.016
0.027
M
3°
3°
C
0.05
4.75
0.15
5.05
0.002
0.187
0.006
0.198
K
N
L
D
8-Pin Plastic MLP-Micro Exposed Pad
LM
MILLIMETERS
INCHES
Dim
MIN
0.80
0.00
0.65
0.15
0.28
2.90
2.90
MAX
1.00
0.05
0.75
0.25
0.38
3.10
3.10
MIN
MAX
0.039
0.002
0.029
0.009
0.015
0.122
0.122
A
A1
A2
A3
b
0.031
0.000
0.025
0.005
0.011
0.114
0.114
L
D
L2
K
D
D2
E
E
e
0.65 BSC
0.025 BSC
E2
D2
E2
K
1.52
1.02
0.20
0.20
0
2.08
1.31
*
0.060
0.040
0.008
0.008
0
0.082
0.052
*
e
b
L2
A
Θ
L
0.60
0.13
12°
0.023
0.005
12°
A2
Internally Connected
together, but isolated
L2
Θ
0°
0°
from all other terminals
A1
A3
Note:
1. Dimensions do not include mold flash or
protrusions;
these
shall
not
exceed
0.155mm(.006”) on any side. Lead dimension
shall not include solder coverage.
Copyright 2000
Microsemi
Page 10
Rev. 1.1, 2002-11-21
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
LX1992
High Efficiency LED Driver
L I N F I N I T Y D I V I S I O N
PRODUCTION
NOTES
PRODUCTION DATA – Information contained in this document is proprietary to
Microsemi and is current as of publication date. This document may not be modified in
any way without the express written consent of Microsemi. Product processing does not
necessarily include testing of all parameters. Microsemi reserves the right to change the
configuration and performance of the product and to discontinue product at any time.
Copyright 2000
Microsemi
Page 11
Rev. 1.1, 2002-11-21
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
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