MICROSEMI LX1742

LX1742
I N T E G R A T E D
P R O D U C T S
High Efficiency High Voltage Boost Controller
P RODUCTION D ATA S HEET
KEY FEATURES
DESCRIPTION
The input voltage ranges from 1.6V to
6.0V, allowing for a wide selection of
system battery voltages. Start-up
operation is guaranteed at 1.6V input
The LX1742 is capable of achieving
output voltages as high as 25V and the
output voltage is easily programmed
using two external resistors in
conjunction with the feedback pin.
The LX1742 has an additional feature
for simple dynamic adjustment of the
output voltage (i.e., up to ±15% of the
nominal output voltage).
Voltage
adjustment is achieved via an analog
reference signal or a direct PWM input
signal applied to the ADJ pin. Any
PWM
amplitude
is
easily
accommodated with a single external
resistor.
ƒ 80% Typical Efficiency
ƒ 80µA Typical Quiescent Supply
Current
ƒ Externally Programmable Peak
Inductor Current Limit For
Maximum Efficiency
ƒ Logic Controlled Shutdown
ƒ < 1.0 µA Shutdown Current (typ)
ƒ Dynamic Output Voltage
Adjustment Via Analog
Reference Or Direct PWM Input
ƒ 8-Pin MSOP Package
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The LX1742 is a compact high
efficiency step-up boost controller.
Featuring a pseudo-hysteretic pulse
frequency modulation topology, the
LX1742 was designed for maximum
efficiency, reduced board size, and
minimal cost.
Utilizing an internal N-Channel
MOSFET,
the
LX1742
offers
designers maximum flexibility with
respect to efficiency and cost. The
LX1742 provides several design
enhancements that improve overall
performance under very light load
currents by implementing control
circuitry that is optimized for portable
systems - thus providing a quiescent
supply current of only 80µA (typ) and
a shutdown current of less than 1µA.
APPLICATIONS/BENEFITS
ƒ
ƒ
ƒ
ƒ
ƒ
ƒ
Pagers
Wireless Phones
PDAs
Handheld Computers
General LCD Bias Applications
LED Driver
IMPORTANT: For the most current data, consult MICROSEMI’s website: http://www.microsemi.com
PRODUCT HIGHLIGHT
VBAT = (1.6V to 6.0V)
UPS530
L1
47µH
VOUT = 18V ± 15%
(For Contrast Adjustment)
SW
IN
OUT
SHDN
LX1742
R1
1MΩ
C2 *
1nF
C1
4.7µF
FB
ADJ
CS
GND
RCS
1kΩ
R2
72kΩ
RPWM
625kΩ
LX1742
100kHz
VPWM = 3.0V
PACKAGE ORDER INFO
Plastic MSOP
DU
8-Pin
TA (°C)
RoHS Compliant / Pb-free
Transition DC: 0432
0 to 70
LX1742CDU
Note: Available in Tape & Reel. Append the letters “TR” to the
part number. (i.e. LX1742CDU-TR)
Copyright © 2000
Rev. 1.0b, 2005-03-03
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 1
LX1742
I N T E G R A T E D
P R O D U C T S
High Efficiency High Voltage Boost Controller
P RODUCTION D ATA S HEET
ABSOLUTE MAXIMUM RATINGS
PACKAGE PIN OUT
SW
1
8
OUT
IN
2
7
GND
FB
3
6
CS
SHDN
4
5
ADJ
DU PACKAGE
(Top View)
RoHS / Pb-free 100% Matte Tin Lead Finish
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.
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Supply Voltage (VIN) ..................................................................................... -0.3V to 7.0V
Output Voltage (OUT) ................................................................................................25.0V
Feedback Input Voltage (VFB) ..............................................................-0.3V to VIN + 0.3V
Shutdown Input Voltage (V SHDN ) ........................................................-0.3V to VIN + 0.3V
PWM Input Amplitude .........................................................................-0.3V to VIN + 0.3V
Analog Adjust Input Voltage (VADJ).................................................................-0.3V to VIN
Source Input Current (ISRC)................................................................................. 500mARMS
Operating Junction Temperature................................................................................ 150°C
Storage Temperature Range.........................................................................-65°C to 150°C
Peak Package Solder Reflow Temp. (40 second max. exposure).................. 260°C (+0, -5)
THERMAL DATA
DU
Plastic MSOP 8-Pin
THERMAL RESISTANCE-JUNCTION TO AMBIENT, θJA
THERMAL RESISTANCE-JUNCTION TO CASE, θJC
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.
FB
Feedback Input – Connect to a resistive divider network between the output and GND to set the output voltage between VCC
(IN) and 25V. The feedback threshold is 1.20V.
SHDN
Active-Low Shutdown Input – A logic low shuts down the device and reduces the supply current to 0.1µA. When
shutdown, the LX1742 isolates the output from the input by turning off the internal MOSFET between LX and OUT.
Connect SHDN to VCC for normal operation.
SW
Inductor Switching Connection – Internally connected to the drain of a 28V N-channel MOSFET. LX is high impedance in
shutdown.
CS
Current-Sense Amplifier Input – Connecting a resistor between CS and GND sets the peak inductor current limit.
Common terminal for ground reference.
ADJ
PWM Signal Input – Connects to the internal reference, via an internal filter and gain resistor, allowing a dynamic output
voltage adjustment ±15% in corresponding to a varying duty cycle. 50% duty cycle yields a nominal output set via the FB
pin (See Note) or ADJ input voltage range from 0.9V to 1.5V DC
OUT
Output voltage is adjustable up to 25V (maximum).
Copyright © 2000
Rev. 1.0b, 2005-03-03
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 2
PACKAGE DATA
GND
LX1742
I N T E G R A T E D
P R O D U C T S
High Efficiency High Voltage Boost Controller
P RODUCTION D ATA S HEET
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 = 3.0V, VADJ = 0V, SHDN = VIN, VFB = 1.0V, Pin 8 = (not connected), Pin 1 = (+5V through 39.2Ω).
Parameter
Symbol
Test Conditions
Min
LX1742
Typ
Units
Max
`
Operating Voltage
Minimum Start-up Voltage
Start-up Voltage Temperature
Coefficient
TA = +25°C
1.6
kVST
Guaranteed: not tested
V SHDN < 0.4V
VADJ = GND
VFB
IFB
FB Threshold Voltage
FB Input Bias Current
ADJ Input Voltage Range
1.175
0
Switching mode
VADJ
1
Shutdown High Input Voltage
Shutdown Low Input Voltage
Current Sense Bias Current
Internal NFET On-resistance
Switch Pin Leakage Current
Switch Off-Time
Diode Forward Voltage
Diode Reverse Current
80
0.5
1.200
0
IADJ
I SHDN
V SHDN
V SHDN
ICS
RDS(ON)
ILEAK
tOFF
VF
IR
ADJ Input Bias Current
Shutdown Input Bias Current
6.0
1.6
V
V
-2
Not Switching
IQ
Quiescent Current
Notes:
1.
2.
VIN
VSU
VADJ = VFB = 1.20V
SHDN = GND
VIN = 2V
VIN = 2V
0
-50
1.6
2.0
TA = +25°C; ISW = 10mA; VFB = 1V
VSW = 25V
VFB = 1V
TA = +25°C; IF = 150mA
TA = +25°C; VR = 25V
mV/°C
100
1.0
1.225
200
µA
µA
V
nA
VIN –
100mV
V
200
50
4.0
1.1
0.23
300
1.0
1.5
0.4
6.0
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ELECTRICAL CHARACTERISTICS
nA
nA
V
V
µA
Ω
µA
ns
V
µA
When using a DC source to adjust VOUT, the recommended VADJ (range) is 0.9V to 1.50V: see figure 9.
Guaranteed typical value (not tested) @ TA=25°C (see section “Inductor Selection & Current Limit Programming”).
SIMPLIFIED BLOCK DIAGRAM
FB
A
ADJ
O ff-time
Controller
SW
OUT
Reference
Logic
B
GND
4µ A
Current
Limiter
CS
Shutdown
Logic
IN
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
SHDN
Page 3
ELECTRICALS
1.2V
Reference
Copyright © 2000
Rev. 1.0b, 2005-03-03
Driver
LX1742
I N T E G R A T E D
High Efficiency High Voltage Boost Controller
P R O D U C T S
P RODUCTION D ATA S HEET
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APPLICATION CIRCUITS
Typical LCD Bias Applications
L1
VBAT = (1.6V to 6.0V)
CR1
UPS5819
47µH
⎛
R ⎞
VOUT = VREF ⎜⎜ 1 + 1 ⎟⎟
R
2⎠
⎝
SW
IN
SHDN
OUT
R1
LX1742
LX1742
C 2*
1nF
FB
ADJ
CS
RCS
4kΩ
GND
C1
10µF
R2
* Optional Component
used to reduce output
voltage ripple.
Figure 1 – Circuit Showing Fixed Output Voltage Operation Using an External Schottky Diode Switch (CR1).
L1
VBAT = (1.6V to 6.0V)
CR1
UPS5819
47µH
⎛
R ⎞
VOUT = VADJ ⎜⎜ 1 + 1 ⎟⎟
⎝ R2 ⎠
SW
IN
OUT
SHDN
LX1742
LX1742
RPWM
100kHz
VPWM = 3.0V
FB
GND
C 2*
1nF
C1
10µF
CS
ADJ
625kΩ
R1
RCS
4kΩ
R2
* Optional Component
used to reduce output
voltage ripple.
Figure 2 – Circuit Showing Dynamic Output Voltage Operation Via PWM Input Using an External Schottky Diode
Switch (CR1).
Copyright © 2000
Rev. 1.0b, 2005-03-03
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
APPLICATIONS
Note: An in-series RPWM will attenuate the PWM amplitude to the proper signal level at the ADJ pin. With the RPWM value shown, a
PWM signal having a duty of 30% to 50% will generate 0.9V to 1.5V at the ADJ pin.
Page 4
LX1742
I N T E G R A T E D
High Efficiency High Voltage Boost Controller
P R O D U C T S
P RODUCTION D ATA S HEET
APPLICATION CIRCUITS (CONTINUED)
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Typical LCD Bias Applications (Cont)
L1
VBAT = (1.6V to 6.0V)
47µH
SW
IN
OUT
SHDN
LX1742
LX1742
+
-
FB
GND
C2*
1nF
C1
10µF
CS
ADJ
VADJ = 0.9V to 1.5V
R1
⎛ R ⎞
VOUT = VADJ ⎜⎜1+ 1 ⎟⎟
⎝ R2 ⎠
RCS
4kΩ
R2
* Optional Component
used to reduce output
voltage ripple.
Figure 3 – Circuit Showing Dynamic Output Voltage Operation Via Analog Voltage Input and Using the Internal Diode
Switch (Optional).
APPLICATIONS
Copyright © 2000
Rev. 1.0b, 2005-03-03
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 5
LX1742
I N T E G R A T E D
P R O D U C T S
High Efficiency High Voltage Boost Controller
P RODUCTION D ATA S HEET
APPLICATION INFORMATION
OUTPUT VOLTAGE PROGRAMMING
Selecting the appropriate values for R1 and R2 in the
voltage divider connected to the feedback pin programs the
output voltage. Using a value between 40KΩ and 75KΩ for
R2 works well in most applications. R1 can be determined
by the following equation (where VREF = 1.29V nominal):
The load is powered from energy stored in the output
capacitor during the inductor charging cycle. Once the peak
inductor current value is achieved, the driver 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.
This causes the output voltage to continue to rise at the
input to the feedback circuit (i.e., comparator A). If the
voltage at the FB input is still less than 1.20V at the end of
the off-time period, the output switches the internal FET
“on” and the inductor charging cycle repeats until VFB is
greater than the internal reference. Typical converter
switching behavior is shown in Figure 11.
INDUCTOR SELECTION AND CURRENT LIMIT
PROGRAMMING
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:
The application of an external voltage source at the ADJ
pin allows for output voltage adjustment over a typical
range of approximately ±15%. The designer can select one
of two possible methods. One option is to vary the
reference voltage directly at the ADJ pin by applying a DC
voltage from 0.9 to 1.5V. The second option is to connect a
PWM logic signal to the ADJ pin (e.g., see Figure 2). The
LX1742 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).
Copyright © 2000
Rev. 1.0b, 2005-03-03
(VOUT - VREF )
VREF
DESIGN EXAMPLE:
Let R2 equals 72K and the required VOUT equal to 18V.
R1 = 72KΩ ×
I PEAK = I MIN
(18V - 1.20V ) = 1.MΩ
1.20V
⎛
⎜
⎜
⎜
⎜
⎜
⎝
+ V IN
L
⎞
⎟
⎟
⎟
⎟
⎟
⎠
⎛
⎞
⎝
⎠
t D + ⎜⎜⎜ I SCALE ⎟⎟⎟ R CS
The maximum IPEAK value is limited by the ISRC value
(max. = 0.8ARMS). The minimum IPEAK value is defined
when RCS is zero. A typical value for the minimum peak
current (IMIN) at 25oC is 104mA. The parameter tD is related
to internal operation of the device. A typical value at 25oC
is 800ns. A typical value of ISCALE at 25oC is 22mA per KΩ.
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.
⎛
⎜
IPEAK =104mA+ ⎜⎜3.0V
⎜⎜
⎝
⎞
⎟
⎟
47µH⎟⎟⎠⎟
⎛
⎞
×800ns+ ⎜⎜⎜22mA ⎟⎟⎟ ×4.02KΩ
⎜
kΩ⎟⎠
⎝
The result of this example yields a nominal IPEAK equal to
243.5mA.
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Page 6
APPLICATIONS
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. If the DC voltage at the ADJ pin drops below
0.6V, the device will revert to the internal reference voltage
level of 1.20V. A typical adjustment curve is shown in
Figure 9 (see section titled: Characteristic Curves). Disabling the LX1742 is achieved by driving the SHDN pin
with a low-level logic signal thus reducing the device power
consumption to less than 1µA.
R1 = R2 ×
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FUNCTIONAL DESCRIPTION
The LX1742 is a Pulse Frequency Modulated (PFM)
boost converter that is optimized for large step up voltage
applications like LCD biasing. It operates in a pseudohysteretic mode with a fixed switch “off time” of 300ns.
Converter switching is enabled when the feedback voltage,
VFB, falls below the 1.20V reference or VADJ (see Block
Diagram). When this occurs, comparator A activates the
off-time controller. The off-time controller and the current
limiting circuits activate comparator B and toggles the
output driver circuit. The 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.
LX1742
I N T E G R A T E D
P R O D U C T S
High Efficiency High Voltage Boost Controller
P RODUCTION D ATA S HEET
APPLICATION INFORMATION (CONTINUED)
VRIPPLE = ∆VDROOP + ∆VOVERSHOOT + 10mV
The initial droop can be estimated as follows where the
1.2 value in the denominator is an estimate of the typical
voltage drop across the inductor and the internal FET’s
RDS_ON:
∆VDROOP
⎛ L ⎞
⎜
⎟ × (IPK × IOUT )
⎜C
⎟
= ⎝ OUT ⎠
(VIN − 1.2)
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:
1
∆VOVERSHOOT =
⎛ L ⎞
⎜
⎟ × (I PK − IOUT )2
⎟
⎝ COUT ⎠
(VOUT + 0.5 − VIN )
2×⎜
DESIGN EXAMPLE:
Determine the VRIPPLE where IPK equals 200mA, IOUT
equals 35mA, L equals 47µH, COUT equals 4.7µF, VIN
equals 3.0V, and VOUT equals 18.0V:
1
∆VOVERSHOOT =
Copyright © 2000
Rev. 1.0b, 2005-03-03
⎛ 47µH ⎞
2
⎟⎟ × (200 mA − 35mA )
⎝ 4.7µF ⎠
= 9.4mV
(18.0 + 0.5 − 3.0)
2 × ⎜⎜
Therefore, for COUT equals 4.7µF:
VRIPPLE = 38mV + 9.4mV + 10mV = 57.4mV
Increasing the output capacitor value results in the
reduction of the output voltage ripple voltage. Low ESR
capacitors are recommended to reduce ripple caused by the
switching current.
Multi-layer ceramic capacitors with
X5R or X7R dielectric are a superior choice featuring small
size, very low ESR, and a temperature stable dielectric.
Low ESR electrolytic capacitors such as solid tantalum or
OS-CON types are also acceptable. Moreover, adding a
capacitor from the output to the feedback pin (C2) allows
the internal feedback circuitry to respond faster which
further minimizes output voltage ripple and reduces noise
coupling into the high impedance feedback input.
DIODE SELECTION
A Schottky diode is recommended for most applications
(e.g. Microsemi UPS5819). The low forward voltage drop
and fast recovery time associated with this type of 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 negative
voltage transition that is greater than VOUT.
The LX1742 has a built in diode that may be used instead of an
external device. Using this internal diode reduces system cost
however, overall efficiency decreases. The electrical connections
corresponding to use of the internal diode are shown in Figure 3.
In this configuration, the inductor is connected between the input
source and the SW pin (1). The output is taken directly from OUT
pin (8).
PCB LAYOUT
The LX1742 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, diode, input and output
capacitors, and feedback connection (i.e., pin 3) are typical
considerations. Moreover, the designer should maximize
the DC input and output trace widths to accommodate peak
current levels associated with this circuit.
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
APPLICATIONS
∆VDROOP
⎛ 47 µH
⎞ × (200mA × 35mA )
⎜
4.7 µF ⎟⎠
⎝
= 38mV
=
(3.0 − 1.2)
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OUTPUT RIPPLE 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
Page 7
LX1742
I N T E G R A T E D
P R O D U C T S
High Efficiency High Voltage Boost Controller
P RODUCTION D ATA S HEET
OVERVIEW
The LXE1742 evaluation board is available from
Microsemi for assessing overall circuit performance. The
evaluation board, shown in Figure 5, is 3 by 3 inches (i.e.,
7.6 X 7.6cm) square and factory calibrated to provide a
nominal 18V output from a 1.6V to 6.0V input. Circuit
designers can easily modify the output voltage and peak
current to suit their particular application by adjusting the
R2, R3, and R4 values accordingly.
Further, other
components are easily swapped out to promote design
verification of any particular circuit application. Table 1
describes the evaluation board’s electrical interface.
ELECTRICAL CONNECTIONS
The system level DC input voltage is applied to VIN.
Connect the test load to VOUT. The Vin & GND terminal
at J4 provides easy test point access. A similar connection is
available for monitoring the output voltage via J5. The
output voltage is adjusted by selecting appropriate values for
R3 and R24. Further adjustment of the output voltage is
achieved by applying either a DC voltage or a PWM-type
signal to the ADJ input (J4).
The evaluation board accommodates both low frequency
(f < 100KHz) and high frequency (f > 100KHz) PWM
signals by connecting either JU1 or JU4 jumper position
respectively. The ADJ pin is easily grounded for fixed
voltage applications by inserting a jumper into the JU5
position. Table 2 provides a complete list of all jumper
positions.
Removing the jumper from the /SHDN position disables
the LX1742 by disconnecting pin 4 from VIN. The load is
still capable of drawing current through the inductor & diode
circuit path when the IC is in shutdown mode. Hence,
VOUT during shutdown will be approximately VIN minus
the inductor and diode forward voltage drop.
The LX1742 can achieve output voltages up to 25V. In
certain applications, it is necessary to protect the load from
excessive voltage excursions.
The evaluation board
provides a zener clamp diode (D1) for this purpose.
The LXE1742 evaluation board offers a cost effective
solution for evaluation of the LX1742. Table 3 provides the
factory installed component list for the evaluation board and
the board schematic is shown in Figure 4.
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EVALUATION BOARD
Table 1: Input and Output Pin Assignments
Name
Application
Range
VIN
0 to 6V
Description
Main power supply input for evaluation board
Vin (J4)
0 to 6V
Connected to VIN (Alternate position or test point)
SHDN (J4)
0 to VIN
Pulled up to VCC on board (10KΩ), Ground to inhibit the LX1742.
Apply a DC input or PWM input to adjust the output voltage (note: see figure 9).
GND (J4)
0 to VIN100mV
0V
GND
0V
ADJ (J4)
0 to VIN
0V
VOUT
VIN to 25V
SWITCH
N/A
/SHDN
0 to VIN
Additional circuit ground connection point.
Apply a DC input or PWM input to adjust the output voltage.
Additional circuit ground connection point.
Output voltage test point. Programmed for 18V output, adjustable up to 25V.
EVALUATION BOARD
FDBK
GND2
Circuit ground
Test point for lX1742 pin 1.
A DC voltage above (below) 1.6V (0.4V) enables (disables) the LX172
Note: All pins are referenced to ground.
Copyright © 2000
Rev. 1.0b, 2005-03-03
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 8
LX1742
I N T E G R A T E D
P R O D U C T S
High Efficiency High Voltage Boost Controller
P RODUCTION D ATA S HEET
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EVALUATION BOARD (CONTINUED)
Table 2: Jumper Pin Position Assignments
Jumper / Position
Function
VIN
n/a
Attach the primary input power form to this contact. Input power may also be applied to the pin marked
Vin on J4.
VOUT
n/a
Use this contact to measure the circuit’s output voltage at pin 8.
SWITCH
n/a
Use this contact to observe the switching waveform at the Schottky anode (i.e., LX1742 pin 1).
FDBK
n/a
Use this contact to measure the circuit’s feedback voltage at pin 3.
GND /
GND2
n/a
Use these contact to connect to circuit ground.
/SHDN
1/0
JU3
1
JU1
1/0/0
JU4
0/1/0
JU5
0/0/1
Inserting a jumper (1) enables the LX1742 by connecting pin 4 directly to VIN. Removing this jumper (0)
disables the LX1742
Remove the factory installed jumper and insert a 4 ~6cm wire loop (optional) to observe the inductor
current waveform using a current probe.
Use this position when adjusting the output with an external PWM that has a repetition rate less than
100KHz. Or when using a DC adjustment voltage.
Use this position when adjusting the output with an external PWM that has a repetition rate in excess of
100KHz.
Use this position to ground the ADJ (pin 5) when using the LX1742 in a fixed output voltage mode
Note: (1) = jumper installed; (0) = jumper not installed.
Table 3: Factory Installed Component List for the LX1742 Evaluation Board
Ref
Part Description
C1
CAPACITOR, 4.7µF, 1210, 35V
C2
CAPACITOR, 4.7µF, 1210, 35V
C3
CAPACITOR, 1000pF, 0805, 35V
C4
CAPACITOR, 2.2µF, 0603, 35V
CAPACITOR, (SPARE); see note 1.
CR1
Microsemi UPS5819, SCHOTTKY, 1A, 40V, POWERMITE
L1
INDUCTOR, 47µH, 480mA, SMT
Q1
MMBT3904 TRANSISTOR, NPN, 40V, SOT-23
D1
BZX84C24, ZENER DIODE, TBD
R1
RESISTOR, 625K, 1/16W, 0805
R2, R5, R6
RESISTOR, 1.0K, 1/16W, 0805
R3
RESISTOR, 1.0M, 1/16W, 0805
R4
RESISTOR, 72K, 1/16W, 0805
R7
RESISTOR, 100K, 1/16W, 0805
U1
Microsemi LX1742CDU BOOST CONTROLLER; see note 2.
Notes
1.
2.
EVALUATION BOARD
C5 & C6
Use these locations to insert additional input (C6) and/or output (C5) capacitance.
The minimum part set for a working power supply consists of: C1, C2, CR1, L1, R2, R3, R4, U1.
Copyright © 2000
Rev. 1.0b, 2005-03-03
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 9
LX1742
I N T E G R A T E D
High Efficiency High Voltage Boost Controller
P R O D U C T S
P RODUCTION D ATA S HEET
EVALUATION BOARD (CONTINUED)
J5
Testpoint
CR1
UPS5819
J4
1
1
Vin
2
/SHDN
3
2
4
1
C1
4.7µF
35V
+
L1
47.0µH
J3
Jumper
+
U1
J2
Jumper
FB
IN
ADJ
J1
R1
Jumper
625K 1
2
J4
Jumper
R6
100K
C4
2.2µF
35V
J5
Jumper
Testpoint
TP3
R4
72K
R2
1K
Q1
MMBT3904/SOT
D4
BZX84C24/SOT
R5
1K
1
C2
4.7µF
35V
Testpoint
GND
LX1742CDU
2
R3
1M
CS
/SHDN
2
C3
1000pF
OUT
SW
1
ADJ
TP2
2
WWW . Microsemi .C OM
TP1
R6
1K
TP4
GND
Testpoint
Figure 4 – LXE1742 Boost Evaluation Board Schematic
Note: Factory installed jumper positions shown
Copyright © 2000
Rev. 1.0b, 2005-03-03
EVALUATION BOARD
Figure 5 – LXE1742 - LX1742 Circuit Evaluation Board
Figure 6 – LXE1742 - Evaluation Board Trace Layout
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 10
LX1742
I N T E G R A T E D
P R O D U C T S
High Efficiency High Voltage Boost Controller
P RODUCTION D ATA S HEET
X4
WWW . Microsemi .C OM
EVALUATION BOARD (CONTINUED)
X3
VIN
L1
SWITCH
Vin
/SHDN
ADJ
CR1
GND
U1
JU1
JU4
R1
GND R7
R2
VOUT
FDBK
Q1
GND2
JU5
Microsemi
LX1742
X1
Figure 7 – LXE1742 - Bottom Trace Layer
EVALUATION BOARD SGE#3503
REV X2
X2
Figure 8 – LXE1742 - Board Layout
EVALUATION BOARD
Copyright © 2000
Rev. 1.0b, 2005-03-03
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 11
LX1742
I N T E G R A T E D
P R O D U C T S
High Efficiency High Voltage Boost Controller
P RODUCTION D ATA S HEET
CHARACTERISTIC CURVES
WWW . Microsemi .C OM
30
100%
25
Efficiency (%)
Output Voltage
90%
20
15
10
80%
70%
5
60%
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
1
1.1 1.2 1.3 1.4 1.5 1.6 1.7
Adj ustment Voltage
50%
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16 17 18 19 20
Output Current
Figure 10 – Efficiency vs. Output Current (mA)
Figure 9 – Typical VOUT versus VADJ
ƒ 0 ~ 0.4V : LX1742 uses internal 1.2V reference.
ƒ 0.5V ~ 0.7V : transition from internal to external reference.
ƒ 0.8 to 1.5V : LX1742 defaults to external voltage reference.
Top: VIN = 3.6V, VOUT = 5.2V, L1 = 47.0µH
Bottom: VIN = 5.5V, VOUT = 18.0V, L1 = 47.0µH
RDS_on (Ohms)
1.40
1.30
1.20
1.10
1.00
0
25
Temperature
75
C
Ch1 – Switch voltage; Ch2 – Output voltage; Ch4 – Inductor current.
(VIN = 3.6V, VOUT = 18V, RLOAD = 2KΩ)
CHARTS
Figure 12 – Typical RDS(on) vs. Temperature
Figure 11 – Typical switching waveforms:
Copyright © 2000
Rev. 1.0b, 2005-03-03
50
o
Condition: VIN = 3.0V; ISW = 10mA
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 12
LX1742
I N T E G R A T E D
High Efficiency High Voltage Boost Controller
P R O D U C T S
P RODUCTION 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
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
NOTES
MECHANICALS
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
Rev. 1.0b, 2005-03-03
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 13