ETC LX1993-02EVALKIT

LX1993
I N T E G R A T E D
High Efficiency LED Driver
P R O D U C T S
P RELIMINARY D ATA S HEET
KEY FEATURES
DESCRIPTION
guaranteed at 1.6V input.
The LX1993 is capable of switching
currents in excess of 300mA and the
output current is readily programmed
using one external current sense
resistor in series with the LEDs. This
configuration provides a feedback
signal to the FB pin thus maintaining
constant output current regardless of
varying LED forward voltage (VF).
The LX1993 provides an additional
feature for simple dynamic adjustment
of the output current (i.e., up to 100%
of the maximum programmed current).
Designers can make this adjustment by
generating an analog reference signal
or a PWM signal applied directly to the
ADJ pin and any PWM amplitude is
readily accommodated via a single
external resistor.
The LX1993 is
available in the 8-Pin MSOP and thus
requires a very small PCB area.
> 80% Maximum Efficiency
70µA Typical Quiescent Supply
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
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The LX1993 is a high efficiency
step-up boost converter that features a
psuedo-hysteretic pulse frequency
modulation topology for driving white
or color LEDs in backlight or
frontlight systems.
Designed for
maximum efficiency, reduced board
size, and minimal cost, the LX1993 is
ideal for PDA and digital camera
applications. The LX1993 features an
internal N-Channel MOSFET and
control circuitry that is optimized for
portable system design applications.
The LX1993 promotes improved
performance
in
battery-operated
systems by operating with a quiescent
supply current 70µA (typical) and a
shutdown current of less than 1µA.
The input voltage range is from 1.6V
to 6.0V thus allowing for a broad
selection
of
battery
voltage
applications
and
start-up
is
APPLICATIONS
Pagers
Wireless Phones
PDAs
Handheld Computers
LED Driver
Digital Camera Displays
IMPORTANT: For the most current data, consult MICROSEMI’s website: http://www.microsemi.com
PRODUCT HIGHLIGHT
SW
IN
OUT
SHDN
Li-Ion
ON OFF
LX1993
FB
CS
ADJ
GND
LX1993
PACKAGE ORDER INFO
Plastic MSOP
TA (°C)
DU 8-Pin
0 to 70
LX1993CDU
Note: Available in Tape & Reel.
Append the letter “T” to the part number. (i.e. LX1993CDUT)
Copyright  2000
Rev. 1.0x, 2002-03-28
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 1
LX1993
I N T E G R A T E D
High Efficiency LED Driver
P R O D U C T S
P RELIMINARY D ATA S HEET
PACKAGE PIN OUT
Supply Voltage (VIN)........................................................................ -0.3V to 7.0V
Feedback Input Voltage (VFB) ................................................ -0.3V to VIN + 0.3V
Shutdown Input Voltage (V SHDN )........................................... -0.3V to VIN + 0.3V
Adjust Input Voltage (VADJ) .................................................... -0.3V to VIN +0.3V
Output Voltage (VOUT) ...................................................................... -0.3V to 25V
Switch Voltage (VSW)........................................................ -0.3V to (VOUT + 1.0V)
Switch Current (ISW)............................................................................. 500mArms
Operating Junction Temperature ..................................................................150°C
Storage Temperature Range .......................................................... -65°C to 150°C
Lead Temperature (Soldering 180 seconds) .................................................235°C
SW
1
8
OUT
IN
2
7
GND
FB
3
6
CS
SHDN
4
5
ADJ
DU P ACKAGE
(Top View)
FRONT MARKING
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.
•
THERMAL DATA
DU
•
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ABSOLUTE MAXIMUM RATINGS
1993
C
MSC
pin 1 indicator
Plastic MSOP 8-Pin
THERMAL RESISTANCE-JUNCTION TO AMBIENT,
THERMAL RESISTANCE-JUNCTION TO CASE,
θJC
θJA
206°C/W
39°C/W
Junction Temperature Calculation: TJ = TA + (PD x θJC).
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
IN
Unregulated IC Supply Voltage Input – Input range from +1.6V to +6.0V. Bypass with a 1µF or greater capacitor
for low voltage operation.
FB
Feedback Input – Connect to a current sense resistor between the load and GND to set the maximum output
current.
SHDN
SW
Inductor Switching Connection – Internally connected to the drain of a 28V N-channel MOSFET. SW is high
impedance in shutdown.
Current-Sense Amplifier Input – Connecting a resistor between CS and GND sets the peak inductor current limit.
GND
Common terminal for ground reference.
ADJ
Output Current Adjustment Input – Provides the internal reference for the output current feedback. The signal
input can be either a PWM signal or analog voltage allowing a dynamic output current adjustment. The signal
should typically range from 500mV to GND, but is capable of an input up to VIN. Caution should be used not to
exceed the device output current rating.
OUT
Output Current - Adjustable up to 25mA. Load voltage should not exceed 25V.
Copyright  2000
Rev. 1.0x, 2002-03-28
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 2
PACKAGE DATA
CS
Active-Low Shutdown Input – A logic low shuts down the device and reduces the supply current to <1µA.
Connect SHDN to VCC for normal operation.
LX1993
I N T E G R A T E D
High Efficiency LED Driver
P R O D U C T S
P RELIMINARY D ATA S HEET
Parameter
Symbol
Test Conditions
Min
LX1993
Typ
Max
Units
`
Operating Voltage
Minimum Start-up Voltage
Start-up Voltage Temperature
Coefficient
VIN
VSU
TA = +25°C
kVST
Guaranteed; not tested
IQ
Quiescent Current
FB Threshold Voltage
FB Input Bias Current
ADJ Input Voltage Range
ADJ Input Bias Current
Shutdown Input Bias Current
Shutdown High Input Voltage
Shutdown Low Input Voltage
Current Sense Bias Current
Minimum Peak Current
Internal NFET On-resistance
Switch Pin Leakage Current
Maximum Switch Off-Time
Diode Forward Voltage
Diode Reverse Current
VFB
IFB
VADJ
IADJ
I SHDN
V SHDN
V SHDN
ICS
IMIN
RDS(ON)
ILEAK
tOFF
VF
IR
1.6
6.0
1.6
-2
Not switching
V SHDN < 0.4V
275
-100
0.0
-150
-100
1.6
Switching VADJ = 0.4V
VADJ < 0.3V
V SHDN = 0V
RCS = 0Ω
TA = +25°C; ISW = 10mA; VFB = 1V
VSW = 25V
VFB = 1V
TA = +25°C; IF = 150mA
TA = +25°C; VR = 25V
3
85
100
70
0.2
300
V
V
mV/°C
100
0.5
325
100
VIN
50
100
5
0.4
7
155
1.1
0.23
300
1.0
1.5
500
µA
µA
mV
nA
V
nA
nA
V
V
µA
mA
Ω
µA
ns
V
µA
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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, VFB = 0.3V, VADJ = 0.2V and SW pin has +5V through 39.2Ω, SHDN =
VIN and CS = GND.
SIMPLIFIED BLOCK DIAGRAM
FB
SW
A1
Reference
Logic
ADJ
50pF
Control
Logic
Driver
GND
2.5M Ω
CS
Shutdown
Logic
IN
ELECTRICALS
4µ A
A2
Copyright  2000
Rev. 1.0x, 2002-03-28
OUT
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
SHDN
Page 3
LX1993
I N T E G R A T E D
High Efficiency LED Driver
P R O D U C T S
P RELIMINARY D ATA S HEET
APPLICATION CIRCUITS
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Typical LED Driver Applications
L1
V BAT = 1.6V to 6.0V
47 µ H
1206 Case Size
C1
1µ F
SW
IN
O UT
ON
OFF
SHDN
LX1993
FB
CS
ADJ
G ND
R CS
1 kΩ
V F = 3.6V typ.
I LED = 20mA to 0mA
R SET
15Ω
Figure 1 – LED Driver with Full-Range Dimming Via PWM Input
L1
V BAT = 1.6V to 6.0V
47 µ H
1206 Case Size
C1
1µ F
SW
IN
OUT
ON
OFF
SHDN
LX1993
FB
ADJ
V ADJ = 0.3V to 0.0V
CS
GND
R CS
1 kΩ
V F = 3.6V typ.
I LED = 20mA to 0mA
RS E T
15Ω
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. 1.0x, 2002-03-28
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 4
APPLICATIONS
+
-
LX1993
I N T E G R A T E D
High Efficiency LED Driver
P R O D U C T S
P RELIMINARY D ATA S HEET
APPLICATION INFORMATION
The LX1993 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 A1 activates the control logic. The control
logic activates the DRV output circuit that connects to the
gate of the internal FET. The output (i.e., SW) 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 input by
comparator A2.
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 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 6, channel 2). This causes the output
voltage to continue to rise across RSET at the input to the
feedback circuit. The LX1993 continues to switch until the
voltage at the FB pin exceeds the control voltage at the
ADJ pin. 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
RSET. The voltage at the FB pin is the product of IOUT (i.e.,
the current through the LED chain) and RSET.
V

R =  ADJmax
SET 
ILEDmax
Copyright  2000
Rev. 1.0x, 2002-03-28
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:
I PEAK = I MIN + 


VIN
L
 t +  ICS
R
 D  R ICS  CS
The maximum IPEAK value is limited by the ISW value
(max. = 500mA rms). The minimum IPEAK value is defined
when RCS is zero. The value range for parameters IMIN and
ICS are provided in the ELECTRICAL CHARACTERISTICS
section of this data sheet. The parameter tD is related to
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.
(
)
(
)
5.0µA
I PEAK = 120mA + 3.0V
× 800ns +
× 4.02KΩ
47µH
200mΩ
The result of this example yields a nominal IPEAK of
approximately 272mA.
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
VRIPPLE = ∆VDROOP + ∆VOVERSHOOT + 10mV
The initial droop can be estimated as follows where the
0.5V value in the denominator is an estimate of the voltage
drop
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 5
APPLICATIONS
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
LX1993 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 LX1993 is achieved by driving the
SHDN pin with a low-level logic signal thus reducing the
device power consumption to approximately 0.5µA (typ).
INDUCTOR SELECTION AND OUTPUT CURRENT LIMIT
PROGRAMMING
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OPERATING THEORY
LX1993
I N T E G R A T E D
High Efficiency LED Driver
P R O D U C T S
P RELIMINARY D ATA S HEET
APPLICATION INFORMATION
∆VDROOP
 L 

 × (I PK × I OUT )
C OUT 

=
Moreover, the designer should maximize the DC input
and output trace widths to accommodate peak current levels
associated with this topology.
EVALUATION BOARD
(VIN − 0.5)
effect the overall efficiency measurement. It is not normally used in an
application; hence, it should not be considered when measuring efficiency.
Copyright  2000
Rev. 1.0x, 2002-03-28
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 6
APPLICATIONS
The LXE1993 evaluation board is available from
Microsemi for assessing overall circuit performance. The
The output overshoot can be estimated as follows where the evaluation board, shown in Figure 3, is 3 by 3 inches (i.e.,
0.5 value in the denominator is an estimate of the voltage 7.6 by 7.6cm) square and programmed to drive 2 to 4 LEDs
drop across the diode:
(provided). Designers can easily modify circuit parameters
to suit their particular application by replacing RCS (as


L
2
1 ×
 × (I PK − IOUT )
2 

described in this section) RSET (i.e., R4) and LED load.
C
 OUT 
∆VOVERSHOOT =
Moreover,
the inductor, FET, and switching diode are easily
(VOUT + 0.5 − VIN )
swapped out to promote design verification of a circuit that
DESIGN EXAMPLE:
maximizes efficiency and minimizes cost for a specific
application.
The evaluation board input and output
Determine the VRIPPLE where IPK equals 200mA, IOUT
connections
are
described in Table 1.
equals 13.0mA, L equals 47µH, COUT equals 4.7µF, VIN
The
DC
input
voltage is applied to VBAT (not VCC)
equals 3.0V, and VOUT equals 13.0V:
however the LX1993 IC may be driven from a separate DC
 47µH 
source via the VCC input. The output current (i.e., LED

 × (200mA × 12.8mA )
brightness) is controlled by adjusting the on-board
4.7µF 

∆VDROOP =
≅ 2.0mV
potentiometer.
The designer may elect to drive the
(13.0 − 0.5)
brightness adjustment circuit from VBAT or via a separate
 47µH 
voltage source by selecting the appropriate jumper position
1 ×
 × (200mA − 12.8mA )2
2 
(see Table 2). Optional external adjustment of the output
4.7
µ
F


∆VOVERSHOOT =
≅ 18.4mV
LED current is achieved by disengaging the potentiometer
(13.0 + 0.5 − 3.0)
and applying either a DC voltage or a PWM-type signal to
Therefore, VRIPPLE = 2.0mV + 18.4mV + 10mV = 30.4mV
the VADJ input. The PWM signal frequency should be
higher than 150KHz and contain a DC component less than
DIODE SELECTION
350mV.
A Schottky diode is recommended for most applications
The LX1993 exhibits a low quiescent current (IQ < 0.5µA:
(e.g., Microsemi UPS5817). The low forward voltage drop
typ) during shutdown mode. The SHDN pin is used to
and fast recovery time associated with this device supports
exercise the shutdown function on the evaluation board.
the switching demands associated with this circuit
This pin is pulled-up to VCC via a 10KΩ resistor.
topology. The designer is encouraged to consider the
Grounding the SHDN pin shuts down the IC (not the circuit
diode’s average and peak current ratings with respect to the
output). The output voltage (i.e., voltage across the LED
application’s output and peak inductor current
string) is readily measured at the VOUT terminal and LED
requirements. Further, the diode’s reverse breakdown
current is derived from measuring the voltage at the VFDBK
voltage characteristic must be capable of withstanding a
pin and dividing this value by 15Ω (i.e., R4).
negative voltage transition that is greater than VOUT.
The factory installed component list for this must-have
PCB LAYOUT
design tool is provided in Table 3 and the schematic is
The LX1993 produces high slew-rate voltage and shown in Figure 4.
Efficiency Measurement Hint: When doing an efficiency evaluation using
current waveforms hence; the designer should take this into
the LX1993 Evaluation Board, VPOT should be driven by a separate voltage
consideration when laying out the circuit. Minimizing
supply to account for losses associated with the onboard reference (i.e., the
trace lengths from the IC to the inductor, diode, input and
1.25V shunt regulator and 1KΩ resistor). This circuit will have VBAT output capacitors, and feedback connection (i.e., pin 3) are
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
typical considerations.
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across the inductor and the FET RDS_ON:
LX1993
I N T E G R A T E D
P R O D U C T S
High Efficiency LED Driver
P RELIMINARY D ATA S HEET
APPLICATION INFORMATION (CONTINUED)
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Figure 3: LXE1993 Engineering Evaluation Board
Table 1: Input and Ouput Pin Assignments
Allowable Range
Description
Pin Name
VBAT
0 to 6V
VCC
1.6V to 6V
VPOT
1.6V to 6V
VADJ IN
0 to 350mV
/SHDN
0 to VCC
Pulled up to VCC on board (10KΩ), Ground to inhibit the LX1992.
VOUT
0 to 18V
Power supply output voltage that is applied to LED string.
VFDBK
0 to 400mV
Jumper Position
Main power supply for output. (Set external current limit to 0.5A)
LX1993 power. May be strapped to VBAT or use a separate supply if VCC jumper is in
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.
Sense resistor voltage. Divide this voltage by 15 to determine LED current.
Table 2: Jumper Pin Position Assignments
Functional Description
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).
VPOT/ VBAT
ADJ/ POT
Use this position when using the potentiometer to adjust LED current.
ADJ/ EXT
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.
LED# OFF
Use this position to short out LED # 3 and / or LED # 4.
APPLICATIONS
VPOT/ SEP
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.
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
LX1993 circuit.
Note: Always put jumpers in one of the two possible positions
Copyright  2000
Rev. 1.0x, 2002-03-28
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 7
LX1993
I N T E G R A T E D
High Efficiency LED Driver
P R O D U C T S
P RELIMINARY D ATA S HEET
APPLICATION INFORMATION (CONTINUED)
Quantity
Part
Reference
1
CR1
1
L1
2
C1, C2
Capacitor, Ceramic X5R, 4.7uF, 25V, 1210 Type SMT
Taiyo Yuden
CETMK325BJ475MN
2
C3, C4
Capacitor, Ceramic X7R, 0.1uF, 50V, 0805 Type SMT
Murata
GRM40X7R104M050
1
R4
Resistor, 15 Ohm, 1/10W, 0805 Type SMT
Panasonic
ERJ6ENF15R0
1
R3
Resistor, 590K, 1/16W, 0603 Type SMT
Panasonic
ERJ3EKF5903
1
R2
Resistor, 100, 1/16W, 0603 Type SMT
Panasonic
ERJ3EKF1000
2
R6, R8
Resistor, 100K, 1/16W, 0603 Type SMT
Panasonic
ERJ3EKF1003
1
R1, R5
Resistor, 10K, 1/16W, 0603 Type SMT
Panasonic
ERJ3EKF1002
1
R7
Bourns
3352E-1-503
1
VR1
IC, Voltage Reference, 1.25 Volts, SOT23 Type SMT
Microsemi
LX432CSC
1
VR2
Diode, Zener, 20V, 1W Powermite Type SMT
Microsemi
1PMT4114
Chicago Miniature
CMD333UWC
3M
929647-09-36
Description
Rectifier, Schottky, 1A, 20V, Powermite Type SMT
Microsemi
UPS5817
Toko
A920CY-470
Inductor, 47uH, 540mA, SMT
Trimpot, 50K, 1/2W, Through Hole Type
4
LED1 - 4
White LED
5
JB1 - JB3
Header, 3 Pos Vertical Type
Part
Number
Manufacturer
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Table 3: Factory Installed Component List for the LX1993 Evaluation Board
5
Jumper
3M
929955-06
Note: The minimum set of parts needed to build a working power supply are: CR1, L1, C1, C2, R2, R4, U1. Evaluation board P/L subject to change
without notice.
CR1
UPS5817
L1
47µH
VBAT
VPOT
VCC
C2
4.7µF
25V
C1
4.7µF
25V
VOUT
GND
CMD333UWC
C3
0.1µF
50V
VCC
IN
SHDN
R1
10k
SW
VR2
20V
1W
1PMT4114
OUT
CMD333UWC
ADJ
FB
GND
CS
LED4 LED3
R2
100Ω
CMD333UWC
ON
OFF
SHDN
CMD333UWC
VFDBK
R3
590K
VADJ
APPLICATIONS
R4
15Ω
VADJ
R5 10k
C4
4.7µF
25V
VPOT
R8
100K
R6
100k
VR1
LX432
R7
50k
Figure 4 – LXE1993 Boost Evaluation Board Schematic
Copyright  2000
Rev. 1.0x, 2002-03-28
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 8
LX1993
I N T E G R A T E D
P R O D U C T S
High Efficiency LED Driver
P RELIMINARY D ATA S HEET
CHARACTERISTIC CURVES
WWW . Microsemi .C OM
365
IPEAK (mA)
340
315
290
265
240
215
190
0
1000
2000
3000
4000
RCS (Ohms)
Figure 5: Example of Peak Current versus RCS value
Figure 6: VOUT and Inductor Current Waveforms.
Channel 1: VOUT (AC coupled; 100mV/div)
Channel 2: Inductor Current (100mA/div.)
4 LED Configuration: VIN = 3.0V
85%
90%
80%
85%
80%
75%
Efficiency
Efficiency
Conditions:
VIN = 2.5V (bottom), 3.3V (middle) & 4.5V (top)
@ TA = 25oC
70%
65%
60%
75%
70%
65%
60%
55%
55%
50%
50%
1
6
11
LED C ur r ent ( mA )
1
16
6
11
LED C ur r ent ( mA )
16
21
Figure 8: Efficiency vs. LED Output Current.
2 LED Configuration: VIN = 5.0V, L = 47µH, RCS = 100Ω
Note: Data taken from LXE1993 Evaluation Board
100%
100%
90%
90%
Efficiency
Efficiency
Figure 7: Efficiency vs. LED Output Current.
2 LED Configuration: VIN = 3.5V, L = 47µH, RCS = 100Ω
Note: Data taken from LXE1993 Evaluation Board
80%
70%
60%
70%
60%
50%
0
5
10
15
LED C ur r ent ( mA )
20
Figure 9: Efficiency vs. LED Output Current.
0
5
10
15
LED C ur r ent ( mA )
CHARTS
50%
20
Figure 10: Efficiency vs. LED Output Current.
4 LED Configuration: VIN = 3.5V, L = 47µH, RCS = 100Ω
Note: Data taken from LXE1993 Evaluation Board
Copyright  2000
Rev. 1.0x, 2002-03-28
80%
4 LED Configuration: VIN = 5.0V, L = 47µH, RCS = 100Ω
Note: Data taken from LXE1993 Evaluation Board
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 9
LX1993
I N T E G R A T E D
P R O D U C T S
High Efficiency LED Driver
P RELIMINARY D ATA S HEET
CHARACTERISTIC CURVES
WWW . Microsemi .C OM
RDS_on (Ohms)
RDS_on (Ohms)
1.40
1.30
1.20
1.10
1.00
1.00
0.90
0.80
0
25
Temperature
50
75
0
o
C
25
Temperature
Figure 11: RDS(on) vs. Temperature
Condition: VIN = 3.0V; ISW = 10mA; TA = 25oC
50
75
o
C
Figure 12: RDS(on) vs. Temperature
Condition: VIN = 5.0V; ISW = 10mA; TA = 25oC
145.00
7.00
140.00
6.00
ICS (µ A)
IMIN (mA)
1.10
135.00
130.00
5.00
4.00
125.00
3.00
0
25
Temperature
50
75
o
C
0
25
Temperature
Figure 13: IMIN versus Temperature.
Condition: VIN = 3.0V
50
75
o
C
Figure 14: ICS versus Temperature.
Condition: VIN = 3.0V
CHARTS
Copyright  2000
Rev. 1.0x, 2002-03-28
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 10
LX1993
I N T E G R A T E D
High Efficiency LED Driver
P R O D U C T S
P RELIMINARY D ATA S HEET
DU
WWW . Microsemi .C OM
PACKAGE DIMENSIONS
8-Pin Miniature Shrink Outline Package (MSOP)
A
Dim
B
H
G
P
M
C
N
Note:
D
L
K
A
B
C
D
G
H
J
K
L
M
N
P
MILLIMETERS
MIN
MAX
2.85
3.05
2.90
3.10
–
1.10
0.25
0.40
0.65 BSC
0.38
0.64
0.13
0.18
0.95 BSC
0.40
0.70
3°
0.05
0.15
4.75
5.05
INCHES
MIN
MAX
.112
.120
.114
.122
–
0.043
0.009
0.160
0.025 BSC
0.015
0.025
0.005
0.007
0.037 BSC
0.016
0.027
3°
0.002
0.006
0.187
0.198
Dimensions do not include mold flash or protrusions; these shall not exceed 0.155mm(0.006”) on any side. Lead dimension shall
not include solder coverage.
MECHANICALS
Copyright  2000
Rev. 1.0x, 2002-03-28
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 11
LX1993
I N T E G R A T E D
P R O D U C T S
High Efficiency LED Driver
P RELIMINARY D ATA S HEET
NOTES
WWW . Microsemi .C OM
NOTES
PRELIMINARY 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
Rev. 1.0x, 2002-03-28
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 12