LX13088
TM
®
Dual 1A Step-Down Converters
P
RODUCTION
D
ATASHEET
KEY FEATURES
•
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
APPLICATIONS
•
Hard Disk Drives
•
Set- Top Boxes
DESCRIPTION
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
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-Before-
Turn-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.
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OM
IMPORTANT:
For the most current data, consult
MICROSEMI’s
website:
http://www.microsemi.com
Product Highlight
LX13088
LX13088
PACKAGE ORDER INFO
THERMAL DATA
T
A
(°C)
0 to +70
LD
Plastic 3x3 mm DFN 10-pin
RoHS Compliant / Pb-free
θ
J
A
=
33
°C/W
THERMAL RESISTANCE
-
JUNCTION TO AMBIENT
LX13088CLD
Note: Available in Tape & Reel. Append the letters “TR” to the part number.
(i.e. LX13088CLD-TR)
Junction Temperature Calculation: T
J
= T
A
+ (P
D
x
θ
JA
).
The
θ
JA
numbers are guidelines for the thermal performance of the
device/pc-board system. All of the above assume no ambient airflow.
Page 1
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
LX13088
TM
®
Dual 1A Step-Down Converters
P
RODUCTION
D
ATASHEET
ABSOLUTE MAXIMUM RATINGS
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 .......................................................... 0
0
C to 150
0
C
Storage Temperature Range..........................................................................–65
0
C to 150
0
C
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.
PACKAGE PIN OUT
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OM
LD P
ACKAGE
(Top View)
Marking
3088
Date/Lot Code
MSC
RoHS / Pb-free 100% Matte Tin Finish
FUNCTIONAL PIN DESCRIPTION
Name
FB2
Pin #
1
Description
Feedback from VO2. Connect voltage divider to the load side of VO2 output inductor-capacitor filter.
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.
Control MOSFET switch power inputs. Connect a 10µF ceramic capacitor between this pin and PGND, as
close to the LX13088 as possible.
Converter 2 synchronous buck switching output. Connect to VO2 inductor.
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.
Converter 1 synchronous buck switching output. Connect to VO1 inductor.
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.
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.
Voltage Monitor – Supervisor for one external voltage (could be input voltage). The POR output is triggered
if this output falls below the VMON threshold.
Feedback from VO1. Connect voltage divider to the load side of VO1 output inductor-capacitor filter.
Analog Ground. Connect the exposed pad on the bottom of the package to the GND plane for a thermal
heat sink.
Page 2
AVIN
2
PVIN
3
SW2
4
PGND
SW1
E/S
POR
VMON
FB1
AGND
5
6
7
8
9
10
PAD
LX13088
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
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 0
0
C < Temp <70
0
C, and the following
test conditions: 4.5
≤
V
VIN
≤
5 .5V, V
PGND
= V
AGND
; E/S = High (Static)
Parameter
Symbol
Test Conditions / Comment
Min
Typ
Max
Units
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Microsemi
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OM
Input Circuitry
Operating Input Voltage
Under Voltage Lockout
UVLO Hysteresis
T
A
= 25°C; not switching; 1.2V = V
FB1
= V
FB2
Input Supply Current
I
VIN
E/S = low
0.1
10
µA
V
VIN
V
VIN
-
UVLO
V
VIN
Rising
4.5
3.0
200
0.01
5.0
3.5
300
0.6
5.5
4.0
400
1
V
V
mV
m
A
VMON Input
POR Threshold VMON
VMON input current
V
VMON-
POR
V
VMON
Falling (hysteresis = 20mV)
V
VMON
= 1.25V
0.97
-100
1.00
0
1.03
100
V
nA
I
VMON
VO1 Output
Feedback Voltage
Peak Current Limit Threshold
PWM Switching Frequency
V
FB1
I
SW1-CT
F
SW1
E/S = static logic high
T
J
= 80°C
Upper FET On Resistance
RDS
SW1-U
T
J
= 25°C
T
J
= 80°C
Lower FET On Resistance
RDS
SW1-L
T
J
= 25°C
Soft Start Time
POR Threshold FB1
Discharge Complete
Threshold
t
SS_FB1
V
FB1-POR
V
FB1-DCT
FB1 Falling (hysteresis = 2% V
FB1
)
FB1 level where discharge cycle is
terminated
0.5
87
50
200
1
89.5
75
2
92
100
ms
%V
FB1
mV
250
mΩ
230
0.975
1.2
1.000
1.6
1.3
275
1.025
V
A
MHz
LX13088
LX13088
VO2 Output
Feedback Voltage
Current Limit
PWM Switching Frequency
Copyright
©
2010
Rev. 1.1, 2010-06-08
V
FB2
I
SW2-CT
F
SW2
E/S = static logic high
0.975
1.2
1.000
1.6
1.3
1.025
V
A
MHz
Page 3
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
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 0
0
C < Temp <70
0
C, and the following
test conditions: 4.5
≤
V
VIN
≤
5 .5V, V
PGND
= V
AGND
; E/S = High (Static)
Parameter
Symbol
Test Conditions / Comment
T
J
= 80°C
Upper FET On Resistance
RDS
SW2-U
T
J
= 25°C
T
J
= 80°C
Lower FET On Resistance
RDS
SW2-L
T
J
= 25°C
Soft Start Time
POR Threshold FB2
Discharge Complete
Threshold
t
SS_FB2
V
FB2-POR
V
FB2-DCT
FB2 Falling (hysteresis = 2% V
FB2
)
FB2 level where discharge cycle is
terminated
0.5
87
50
150
1
90
75
2
92
100
ms
%V
FB2
mV
250
mΩ
155
Min
Typ
240
Max
Units
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OM
E/S
E/S Threshold
V
E/S - H
V
E/S - L
E/S Leakage Current
I
E/S
F
E/S - MIN
Frequency lock in range
F
E/S -MAX
Shutdown delay
t
E/S-SHDN
0 < V
E/S
< V
VIN
Switching frequency is ½ E/S frequency
when externally clocked.
Shutdown initiated if logic low is of longer
duration than delay.
-100
1.5
0.6
100
1.5
MHz
3.0
2
4
10
µs
V
V
nA
POR
POR Assert Delay Time
POR Release Delay Time
POR Low Voltage
POR High Leakage
t
POR_DELAY
t
POR_HOLD
V
POR_LOW
I
POR_HI
Fault Flag set to POR pull low
Fault Flag reset to POR Hi-Z state
POR sinking 4mA
POR High Level
10
25
20
200
0.003
30
300
1
µs
ms
mV
µA
LX13088
LX13088
Power Up Sequencing
VO2 Start Threshold
V
FB1-ST
FB1 rising voltage for FB2 to initiate soft start
87
90
92
%V
FB1
Brown Out Discharge
SW1, SW2 Discharge
Resistance
SW1, SW2 Discharge
Resistance matching
Copyright
©
2010
Rev. 1.1, 2010-06-08
R
STOP-
SW1,2
Discharge Resistance for SW1 and VO2
15
0.90
30
1
45
1.1
Ω
R
STOP-SW1
/
R
STOP-
SW2
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 4
LX13088
TM
®
Dual 1A Step-Down Converters
P
RODUCTION
D
ATASHEET
SYSTEM CHARACTERISTICS
Unless otherwise specified, the following specifications apply over the operating ambient temperature of 0
0
C < Temp <70
0
C, and the following
test conditions:, 4.5
≤
V
VIN
≤
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.
Parameter
Symbol
Test Conditions / Comment
Min
Typ
Max
Units
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Microsemi
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OM
VO1 Output
Line Regulation
Load Regulation
Dynamic Load Response
VO1
VO1
VO1
I
SW1(avg)
= 300mA;
4.50V < V
VIN
< 5.50V
0.1
0.5
-5
87
94
82
%
+5
%
%
%VO
1
5mA < I
SW1(avg)
< 1000mA
Transient Response = 500mA step anywhere
within 10mA to 1000mA range,
∆I
/
∆t
= 1A/µs
I
SW1(avg)
= 1000mA; VO1= 2.5V
Efficiency
(L
1
DCR = 44mΩ)
η
VO1
I
SW1(avg)
= 200mA ; VO1= 2.5V
I
SW1(avg)
= 10mA; VO1= 2.5V
VO2 Output
Line Regulation
Load Regulation
VO2
VO2
I
SW2(avg)
= 300mA;
4.50V < V
VIN
< 5.50V
0.1
0.5
80
90
%
I
SW2(avg)
= 10mA; VO2= 1.2V
75
%
%
%
5mA < I
SW2(avg)
≤
1000mA
I
SW2(avg)
= 1000mA; VO2= 1.2V
Efficiency
(L
2
DCR = 44mΩ )
η
VO2
I
SW2(avg)
= 200mA; VO2= 1.2V
Thermal Shutdown
Thermal Shutdown Threshold
Thermal Shutdown Hysteresis
160
20
°C
°C
LX13088
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
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