Microsemi LX13088CLD-TR Dual 1a step-down converter Datasheet

LX13088
®
TM
Dual 1A Step-Down Converters
P RODUCTION D ATASHEET
DESCRIPTION
synchronized to an external clock. With
the E/S input held low, the LX13088
draws less than 10uA.
Both converters have controlled soft
start, in addition to power up sequencing.
In the start-up sequence, the output of
converter 1 is designed to precede the
output of converter 2.
Power On Reset function is provided
by means of an open-drain output at the
POR pin. The Power On Reset function
monitors the voltages at the VMON, FB1
and FB2 pins, and pulls low if any of
these voltages drop below the stated POR
threshold. The POR is internally
deglitched and provides a delayed
recovery and reset time.
The LX13088 provides peak over
current protection, short circuit protection
and thermal shutdown. Discharge-BeforeTurn-On
discharges
the
outputs
completely before soft starting to always
bring them up in the proper sequence at
start up or after a POR event.
• Outputs can be set from 1V to
3.6V @ 1A
• No Rectifier Diode required
• 1.3MHz Switching
• 180° Phase Shifted Switching
• Optional External Clocking (2x
clock required)
• Light load Pulse Skipping
• Enable/Sleep state
• Internal Soft Start
• Open-drain Power On Reset
Monitors Input and Outputs
• Discharge Before-Turn-On
• Peak Over-Current Protection
• Short Circuit Protection
• Over Temperature Shutdown
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The LX13088 is a highly integrated
dual output voltage regulator ideal for
low power applications that require
minimal board space. The two current
mode buck converters include integrated
high side control switches, synchronous
rectifiers, and internal compensation.
The outputs of each converter are both
rated for up to 1A, and the output
voltages are adjustable using external
resistive dividers.
The LX13088 step down converters
operate at 1.3MHz fixed switching
frequency under normal load, reducing
external output filter component values
and size. Under light load conditions, the
converters operate in a pulse-skipping
mode for improved efficiency.
The LX13088 incorporates out of
phase switching, where converter 2
switches 180° out of phase from
converter 1 in order to minimize the input
ripple effects.
The controller also
features an E/S pin that provides an
enable input function, or allows the
converter to be
KEY FEATURES
APPLICATIONS
• Hard Disk Drives
• Set- Top Boxes
IMPORTANT: For the most current data, consult MICROSEMI’s website: http://www.microsemi.com
Product Highlight
TA (°C)
0 to +70
LD
THERMAL DATA
Plastic 3x3 mm DFN 10-pin
θJA = 33 °C/W
RoHS Compliant / Pb-free
THERMAL RESISTANCE-JUNCTION TO AMBIENT
LX13088CLD
Junction Temperature Calculation: TJ = TA + (PD x θJA).
The θJA numbers are guidelines for the thermal performance of the
device/pc-board system. All of the above assume no ambient airflow.
Note: Available in Tape & Reel. Append the letters “TR” to the part number.
(i.e. LX13088CLD-TR)
Copyright © 2010
Rev. 1.1, 2010-06-08
LX13088
PACKAGE ORDER INFO
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 1
LX13088
®
TM
Dual 1A Step-Down Converters
P RODUCTION D ATASHEET
ABSOLUTE MAXIMUM RATINGS
PACKAGE PIN OUT
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PVIN, AVIN to AGND, PGND...................................................................... -0.3 to +7.0 V
SW1 and SW2 to AGND, PGND .................................................. PGND -2V to xVIN+2V
All other pins to AGND.................................................................... -0.3V to xVIN + 0.3V
Operating Junction Temperature Range .......................................................... 00C to 1500C
Storage Temperature Range..........................................................................–650C to 1500C
0
Package Peak Temp. for Solder Reflow (40 seconds maximum exposure) .. 260°C (+0 -5) C
Notes: 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. PGND must be wired to AGND
externally.
LD PACKAGE
(Top View)
Marking
3088
Date/Lot Code
MSC
RoHS / Pb-free 100% Matte Tin Finish
FUNCTIONAL PIN DESCRIPTION
Name
Pin #
Description
1
Feedback from VO2. Connect voltage divider to the load side of VO2 output inductor-capacitor filter.
AVIN
2
Analog Input. Input to power the internal circuitry of the device, connect to PVIN through a 10Ω resistor and
bypass through a 1μF ceramic capacitor between this pin and PGND, as close to the LX13088 as possible.
PVIN
3
Control MOSFET switch power inputs. Connect a 10µF ceramic capacitor between this pin and PGND, as
close to the LX13088 as possible.
SW2
4
Converter 2 synchronous buck switching output. Connect to VO2 inductor.
PGND
5
Power Ground Connection. Synchronous rectifier MOSFET source. Provide a star connection between this
pin, VO1, VO2 filter capacitor returns, VIN input capacitor return, and AGND. Keep the star connection as
close to the LX13088 IC as possible.
SW1
6
Converter 1 synchronous buck switching output. Connect to VO1 inductor.
E/S
7
Enable/Synchronization. Pulling this pin high statically enables the LX13088 and pulling the pin low
statically will shut down the LX13088. Applying a pulse to this pin will synchronize SW1 and SW2 switching
frequency to ½ the external clock frequency.
POR
8
Power On Reset output pin. Monitors FB1, FB2 output voltage levels and VIN. POR is pulled low if an
output voltage droop is detected on FB1 or FB2 or VIN, and is Hi-Z during normal operation.
VMON
9
Voltage Monitor – Supervisor for one external voltage (could be input voltage). The POR output is triggered
if this output falls below the VMON threshold.
FB1
10
Feedback from VO1. Connect voltage divider to the load side of VO1 output inductor-capacitor filter.
AGND
PAD
Copyright © 2010
Rev. 1.1, 2010-06-08
Analog Ground. Connect the exposed pad on the bottom of the package to the GND plane for a thermal
heat sink.
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Page 2
LX13088
FB2
LX13088
®
TM
Dual 1A Step-Down Converters
P RODUCTION D ATASHEET
ELECTRICAL CHARACTERISTICS
Parameter
Symbol
Test Conditions / Comment
Min
Typ
Max
Units
4.5
5.0
5.5
V
3.0
3.5
4.0
V
200
300
400
mV
0.01
0.6
1
mA
0.1
10
µA
Input Circuitry
Operating Input Voltage
VVIN
Under Voltage Lockout
VVIN-UVLO
VVIN Rising
UVLO Hysteresis
TA = 25°C; not switching; 1.2V = VFB1 = VFB2
Input Supply Current
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Unless otherwise specified, the following specifications apply over the operating ambient temperature of 00C < Temp <700C, and the following
test conditions: 4.5 ≤ VVIN ≤ 5 .5V, VPGND = VAGND ; E/S = High (Static)
IVIN
E/S = low
VMON Input
VVMON-
POR Threshold VMON
VVMON Falling (hysteresis = 20mV)
0.97
1.00
1.03
V
VVMON = 1.25V
-100
0
100
nA
VFB1
0.975
1.000
1.025
V
ISW1-CT
1.2
1.6
A
E/S = static logic high
1.3
MHz
TJ = 80°C
275
TJ = 25°C
250
TJ = 80°C
230
TJ = 25°C
200
POR
VMON input current
IVMON
VO1 Output
Feedback Voltage
Peak Current Limit Threshold
PWM Switching Frequency
FSW1
Upper FET On Resistance
RDSSW1-U
mΩ
Lower FET On Resistance
Soft Start Time
RDSSW1-L
tSS_FB1
0.5
1
2
ms
VFB1-POR
FB1 Falling (hysteresis = 2% VFB1)
87
89.5
92
%VFB1
Discharge Complete
Threshold
VFB1-DCT
FB1 level where discharge cycle is
terminated
50
75
100
mV
VFB2
0.975
1.000
1.025
V
ISW2-CT
1.2
1.6
A
1.3
MHz
VO2 Output
Feedback Voltage
Current Limit
PWM Switching Frequency
Copyright © 2010
Rev. 1.1, 2010-06-08
FSW2
E/S = static logic high
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Analog Mixed Signal Group
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Page 3
LX13088
POR Threshold FB1
LX13088
®
TM
Dual 1A Step-Down Converters
P RODUCTION D ATASHEET
ELECTRICAL CHARACTERISTICS
Unless otherwise specified, the following specifications apply over the operating ambient temperature of 00C < Temp <700C, and the following
test conditions: 4.5 ≤ VVIN ≤ 5 .5V, VPGND = VAGND ; E/S = High (Static)
Upper FET On Resistance
Symbol
Test Conditions / Comment
Min
Typ
TJ = 80°C
240
TJ = 25°C
250
TJ = 80°C
155
TJ = 25°C
150
Max
Units
RDSSW2-U
mΩ
Lower FET On Resistance
Soft Start Time
RDSSW2-L
tSS_FB2
0.5
1
2
ms
POR Threshold FB2
VFB2-POR
FB2 Falling (hysteresis = 2% VFB2)
87
90
92
%VFB2
Discharge Complete
Threshold
VFB2-DCT
FB2 level where discharge cycle is
terminated
50
75
100
mV
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Parameter
E/S
E/S Threshold
1.5
VE/S - H
V
VE/S - L
E/S Leakage Current
I E/S
FE/S - MIN
Frequency lock in range
FE/S -MAX
Shutdown delay
tE/S-SHDN
0 < V E/S < VVIN
Switching frequency is ½ E/S frequency
when externally clocked.
Shutdown initiated if logic low is of longer
duration than delay.
-100
0.6
V
100
nA
1.5
MHz
3.0
2
4
10
µs
POR
POR Assert Delay Time
tPOR_DELAY
Fault Flag set to POR pull low
POR Release Delay Time
tPOR_HOLD
Fault Flag reset to POR Hi-Z state
POR Low Voltage
VPOR_LOW
POR sinking 4mA
POR High Leakage
25
10
µs
20
30
ms
200
300
mV
0.003
1
µA
POR High Level
VFB1-ST
FB1 rising voltage for FB2 to initiate soft start
87
90
92
%VFB1
Discharge Resistance for SW1 and VO2
15
30
45
Ω
0.90
1
1.1
Power Up Sequencing
VO2 Start Threshold
Brown Out Discharge
SW1, SW2 Discharge
Resistance
SW1, SW2 Discharge
Resistance matching
Copyright © 2010
Rev. 1.1, 2010-06-08
RSTOPSW1,2
RSTOP-SW1
/ RSTOPSW2
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Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 4
LX13088
IPOR_HI
LX13088
Dual 1A Step-Down Converters
®
TM
P RODUCTION D ATASHEET
SYSTEM CHARACTERISTICS
Parameter
Symbol
Test Conditions / Comment
Min
Typ
Max
Units
VO1 Output
Line Regulation
VO1
ISW1(avg) = 300mA;
4.50V < VVIN < 5.50V
Load Regulation
VO1
5mA < ISW1(avg) < 1000mA
Dynamic Load Response
VO1
Transient Response = 500mA step anywhere
within 10mA to 1000mA range, ∆I / ∆t = 1A/µs
ηVO1
%
0.5
%
-5
ISW1(avg) = 1000mA; VO1= 2.5V
Efficiency
(L1 DCR = 44mΩ)
0.1
ISW1(avg) = 200mA ; VO1= 2.5V
ISW1(avg) = 10mA; VO1= 2.5V
+5
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Unless otherwise specified, the following specifications apply over the operating ambient temperature of 00C < Temp <700C, and the following
test conditions:, 4.5 ≤ VVIN ≤ 5.5V, E/S = High. Configured per application circuit. System Characteristics are closed loop tests that are
verified as part of characterization but are not tested in production.
%VO
1
87
94
%
82
VO2 Output
Line Regulation
VO2
ISW2(avg) = 300mA;
Load Regulation
VO2
Efficiency
(L2 DCR = 44mΩ )
ηVO2
4.50V < VVIN < 5.50V
0.1
%
5mA < ISW2(avg) ≤ 1000mA
0.5
%
ISW2(avg) = 1000mA; VO2= 1.2V
80
%
ISW2(avg) = 200mA; VO2= 1.2V
90
ISW2(avg) = 10mA; VO2= 1.2V
75
%
Thermal Shutdown
Thermal Shutdown Threshold
160
°C
Thermal Shutdown Hysteresis
20
°C
LX13088
Copyright © 2010
Rev. 1.1, 2010-06-08
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 5
LX13088
®
TM
Dual 1A Step-Down Converters
P RODUCTION D ATASHEET
STARTUP SEQUENCING
SOFTSTART
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Soft start showing converter 1, VOUT1=1.2V at 1A
VOUT1=1.2V, VOUT2=2.5V, both outputs loaded at 1A
DYNAMIC LOAD
EFFICIENCY
Copyright © 2010
Rev. 1.1, 2010-06-08
Efficiency for 2.5V and 1.2V output voltages, VIN=5V
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Page 6
LX13088
VOUT1=1.2V, output 1 load transition from 0.5A to 1A
LX13088
TM
Dual 1A Step-Down Converters
®
P RODUCTION D ATASHEET
STARTUP AFTER OUTPUT DISCHARGE
SYNCHRONIZATION
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Outputs must discharge to <10% before repeat startup
Synchronization & out of phase, 3MHz CLK IN at E/S Input
CURRENT LIMIT & SHORT CIRCUIT
Copyright © 2010
Rev. 1.1, 2010-06-08
Both outputs loaded at 1A, peak to peak output ripple is
~10mV
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LX13088
VOUT1 shorted to ground continuously after normal
regulation
OUTPUT RIPPLE
LX13088
TM
®
Dual 1A Step-Down Converters
P RODUCTION D ATASHEET
FUNCTION BLOCK DIAGRAM
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LX13088
Figure 1. Functional Block Diagram
Copyright © 2010
Rev. 1.1, 2010-06-08
Microsemi
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11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
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LX13088
TM
®
Dual 1A Step-Down Converters
P RODUCTION D ATASHEET
WWW . Microsemi .C OM
TYPICAL APPLICATION
Figure 2. Typical Application Circuit
LX13088
Copyright © 2010
Rev. 1.1, 2010-06-08
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
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LX13088
TM
Dual 1A Step-Down Converters
®
P RODUCTION D ATASHEET
THEORY OF OPERATION
POR
Under-voltage comparators are provided to monitor the output
voltages and the voltage at VMON which could be the input
supply voltage. If any of these voltages falls below its POR
threshold, the POR open drain output will turn on which pulls
the POR pin low. Note that the fault to POR assert delay time is
approximately 20µS. If the POR fault condition is cleared,
there is a delay of 20ms before the POR output transistor is
turned off; when off the POR pin is high Z and may be pulled
up high via a resistor.
The POR function has built in deglitching. Once the POR is
detected, the power supply outputs will be discharged prior to a
restart condition, where soft start and power up sequencing will
occur.
OUTPUT DISCHARGE
After the occurrence of a POR situation, and the POR fault
condition is immediately cleared, startup and soft start is
delayed until the outputs are discharge to <10%. During the
discharge phase, the soft start internal reference voltages
(REFx) are shorted to ground to quickly discharge it. The output
capacitors are discharged via an internal 30Ω pull down switch
on each of the SW1 and SW2 pins. When the FBx voltage and
the REFx voltage are fully discharged and if there is not an OT
condition, the outputs are then allowed to begin the normal soft
start power up sequence. During the discharge phase, the
control high side and synchronous rectifier MOSFETs are in the
high-Z off state.
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LX13088
SOFTSTART
The DC-DC converters contain a soft start function that
brings the output voltages up via a slowly increasing ramp with
any resistive load from open circuit to 1A. The output voltage
waveform shall not vary by more than 50mV from a straight
line drawn from the initial voltage to the final steady state
voltage. During soft start, the peak inductor current shall not
exceed 750mA until the output voltage reaches 25% of its final
value. Current limit shall be active but not trip during soft start
into a rated resistive load. Overshoot voltage during soft start
OVER CURRENT AND SHORT CIRCUIT PROTECTION
is limited to 1%.
The DC-DC converters have over current and short circuit
protection. During any mode of operation, any value of load
ENABLE AND POWER UP SEQUENCING
resistance (including 0 ohms) can be applied to the DC-DC
When power is applied at VIN and if the E/S input is asserted outputs instantaneously and held in place indefinitely without
(High) or is toggling, the DC-DC converters will enter RUN the switch current exceeding the peak current limit and without
mode after a short settling period. If the E/S pin is a static low, the IC suffering any permanent damage or loss of performance.
the IC will enter a SLEEP state where it draws very little input The output voltage is allowed to drop under over current or
current, less than 10uA.
short circuit conditions. Both converters will stop switching if
When in RUN mode, if there is no fault condition, the VO1 either one experiences an over current condition for various
output of converter 1 will be the first output to begin soft start. cycles.
When the reference voltage for FB1 reaches approximately 90%
Recovery to output voltage regulation occurs within 10ms of
of the final value, the VO2 output of converter 2 will begin soft the instant the loading is reduced to maximum allowable rated
start.
load; the output voltage shall not exceed the dynamic load
excursion limits (+/-5% excursion) upon recovery.
Copyright © 2010
Rev. 1.1, 2010-06-08
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DC-DC SWITCHING STEP DOWN CONVERTERS
The LX13088 dual DC-DC converters are current mode buck
converters with integrated high side switch, synchronous
rectifier and internal compensation. They are designed to be
stable with a3.3µH inductor value and 10µF to 22µF output
capacitor. Both output voltages are resistor divider
programmable. The switching frequency of the converter is
fixed and the switches turn on at alternating 180° phase
intervals.
The converters operate in 3 possible modes: continuous mode
(CM), discontinuous mode (DM), and pulse skipping mode
(PSM). CM is the default mode under normal loading. DM
occurs under light loads, where switching still occurs at the
programmed frequency. In DM, a zero crossing detector shuts
off the synchronous rectifier to prevent reverse rectifier current;
this results in a portion of the switch period where neither
switch is on. Under very light loads, PSM mode occurs, where
switching cycles are skipped if the current demand is low in
order to provide better efficiency.
LX13088
Dual 1A Step-Down Converters
®
TM
P RODUCTION D ATASHEET
OPERATION
The total power dissipated by the LX13088 device, PTOTAL,
will be comprised of the power dissipated by the RMS current
flowing through the internal high-side FET during the duty
cycle D time, by the RMS current flowing through the
synchronous rectifier during 1-D time, by the switching or
transitioning of the FET, and of the power dissipated by the
device supply current.
INDUCTOR SELECTION
A 3.3µH ±20% inductor is suggested as the internal
compensation has been optimized around this inductor value. A
3.3µH is a good compromise, since for an output voltage
ranging from VOUT = 1V to VOUT = 4V, loaded at 1A, the
LIR or the ratio of inductor ripple current to output load will
range from about 20% to 30%, assuming VIN = 5V and the
converter switching at 1.3MHz.
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E/S DECODER LOGIC
The E/S pin serves a dual purpose. It will enable the IC if it
detects either a valid clock signal or a static high logic level. A
static low logic level for longer than 4µs is determined to be a
shutdown signal. The decode logic is shown below. The Oneshot function will produce a logic high output (Clock Detect) as
long as the E/S pin is toggling. Clock Detect is used to keep
ENABLE high and to select the E/S clock as the system clock.
If E/S is a static high (non-toggling) input, the retriggerable
one-shot will go low after 4µs; this will set Clk Det low and
select the internal oscillator as the system clock.
OUTPUT CAPACITOR
To ensure stability and good load transient response, use at
least a 10µF output capacitor for converter 1, and a 20µF or
greater for converter 2. Output ceramics capacitors with low
ESR are suitable.
SETTING THE OUTPUT VOLTAGE
The LX13088 converter’s maximum duty cycle is
SYNCHRONIZATION
approximately 90%. For a 5V input, 90% duty cycle will be
The converters can be synchronized to an external system achieved for an output voltage of about 4V loaded at 1A.
clock present at the E/S input pin. During synchronization, the
converter’s switching frequency will be ½ the frequency of the
To set the output voltage, connect a resistive divider from the
external clock, and the two converters will still be 180 degrees
out of phase. The lock in frequency for synchronization is output to the FBx pin to signal ground. Note that the feedback
specified to be between 1.5MHz to 3MHz, minimum sync pulse voltage is 1.0V. For the desired output voltage VOUT, the
upper resistor from VOUT to FB (RUPPER) is calculated by the
width is 100ns.
following equation:
(
T =T + P
×θ
TOTAL
JA
J
A
Copyright © 2010
Rev. 1.1, 2010-06-08
)
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 11
LX13088
OVER TEMPERATURE PROTECTION
⎛ VOUT ⎞
If an over temperature fault occurs, the DC-DC converter will
R
=R
×⎜
− 1⎟
UPPER LOWER ⎝ VFB
⎠
stop switching and the SW# outputs will become high
impedance. Note that the temperature fault occurs at a die RLOWER, or the resistor from FBx pin to ground, is selected to be
temperature of approximately 160˚C. When the IC cools down, 20kΩ. VFB = 1V, and VOUT is chosen by the designer for the
it will attempt to resume switching. If a POR is activated as a given application.
result of the OT situation, restart will be subject to the soft
start/sequencing routine and will not occur until the OT
condition has been corrected.
The device junction temperature is a function of the device’s
total power dissipation, the junction to ambient thermal
resistance, and the ambient temperature:
LX13088
Dual 1A Step-Down Converters
®
TM
P RODUCTION D ATASHEET
PACKAGE DIMENSIONS
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LD
10-Pin Plastic MLP Dual Exposed Pad
D
e
Dim
A
A1
A3
b
D
D2
e
E
E2
L
L
E
E2
Top View
Bottom
View
b
D2
MILLIMETERS
MIN MAX
0.80 1.00
0
0.05
0.20 REF
0.18 0.30
3.00 BSC
2.23 2.48
0.50 BSC
3.00 BSC
1.49 1.74
0.30 0.50
INCHES
MIN
MAX
0.0315 0.0394
0
0.0019
0.0079 REF
0.0071 0.0118
0.1181 BSC
0.0878 0.0976
0.0197 BSC
0.1181 BSC
0.0587 0.0685
0.0071 0.0197
Note:
A
A3
A1
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.
LX13088
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 © 2010
Rev. 1.1, 2010-06-08
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
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