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LX1675CLQ-TR

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P19
LX1675
PRODUCTION DATA SHEET
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 1
Copyright © 2004
Rev. 1.2a, 2006-02-16
WWW.Microsemi .COM
Multiple Output LoadSHARE™ PWM
TM
®
DESCRIPTION
The LX1675 is a highly integrated
power supply controller IC featuring
three voltage mode PWM switching
regulator stages with an additional
onboard linear regulator driver.
Two of the constant frequency PWM
phases can be easily configured for a
single Bi-Phase high current output or
operated as two independently regulated
outputs. All outputs (PWM phases and
LDO) have separate, programmable soft-
start sequencing. This versatility yields
either three or four independently
regulated outputs with full power
sequencing capability giving system
designers the ultimate flexibility in power
supply design.
Current limit for each PWM regulator
is provided by monitoring the voltage
drop across the lower MOSFET power
stage during conduction, utilizing the
Rds(on) impedance. This eliminates the
need for expensive current sense
resistors. Once current limit has been
reached and persist for 4 clock cycles, the
output is shut off and Soft Start is
initialized to force a hiccup mode for
protection.
High current MOSFETs can be directly
driven to provide an LDO output of 5A
and 15A for each PWM controller. This
is useful for I/O, memory, termination,
and other supplies surrounding today’s
micro-processor based designs.
The LX1675 accepts a wide range of
supply voltage ranging from 4.5V to 24V.
Each PWM regulator output voltage is
programmed via a simple voltage-divider
network. The LX1675 design gives
engineers maximum flexibility with
respect to the MOSFET supply. Each
phase can utilize different supply voltages
for efficient use of available supply rails.
Additionally, when two phases are
configured in Bi-Phase output, the
LoadSHARE
™
topology can be
programmed via inductor ESR selection.
The split phase operation reduces power
loss, noise due to the ESR of the input
capacitors and allows for reduction in
capacitance values while maximizing
regulator response time. The internal
reference voltage is buffered and brought
out on a separate pin to be used as an
external reference voltage.
IMPORTANT: For the most current data, consult MICROSEMI’s website: http://www.microsemi.com
LoadSHARE is a Trademark of Microsemi Corporation
Protected by U.S. Patents 6,285,571 and 6,292,378
KEY FEATURES
Four Independently Regulated
Outputs
Single Input Supply with Wide
Voltage Range: 4.5-24V
Outputs As Low As 0.8V
Generated From a Precision
Internal Reference
Selectable PWM Frequency of
300KHz or 600KHz
Buffered Reference Voltage
Output
Multiphase Output Reduces
Need for Large Input
Capacitance at High Currents
Integrated High Current
MOSFET Drivers
Independent Soft-Start and
Power Sequencing
Adjustable Linear Regulator
Driver Output
No Current-Sense Resistors
DDR Termination Compliant
RoHS Compliant for Pb Free
APPLICATIONS
Multi-Output Power Supplies
Video Card Power Supplies
PC Peripherals
Portable PC Processor and I/O
Supply
PRODUCT HIGHLIGHT
HOX
5µh
VIN
VOUT1, 2, 3
FBX
EOX
VIN 4.5V to 24V
VCCL
ONE OF 3 PWM SECTIONS
LX1675
VOUT4
CSX
VCX
HRX
LOX
SSX
VSLR
PGX
AGND
LDGD
LDFB
PACKAGE ORDER INFO
LQ
Plastic MLPQ
38-Pin
T
A
(°C)
RoHS Compliant / Pb-free
0 to 85
LX1675CLQ
-40 to 85
LX1675ILQ
Note: Available in Tape & Reel. Append the
letters “TR” to the part number. (i.e.
LX1675CLQ-TR)
L
L
X
X
1
1
6
6
7
7
5
5
LX1675
PRODUCTION DATA SHEET
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 2
Copyright © 2004
Rev. 1.2a, 2006-02-16
WWW.Microsemi .COM
Multiple Output LoadSHARE™ PWM
TM
®
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (VIN
,
VSLR, HRX)............................................................... -0.3V to 24V
Supply Voltage (VCCL) ................................................................................ -0.3V to 6.0V
Driver Supply Voltage (VCX)........................................................................ -0.3V to 30V
Current Sense Inputs (CSX)............................................................................ -0.3V to 30V
Error Amplifier Inputs (FB
X
, RF2, LDFB).................................................... -0.3V to 5.5V
Internal regulator Current (I
VCCL
)............................................................................... 50mA
Output Drive Peak Current Source (HO
X
, LO
X
)................................................ 1A (200ns)
Output Drive Peak Current Sink (HO
X
, LO
X
)................................................. 1.5A (200ns)
Differential Voltage: V
HOX
– V
HRX
(High Side Return).................................... -0.3V to 6V
Soft Start Input (SSX, SSL)............................................................................-0.3V to V
REF
Logic Inputs (SF, FS)..........................................................................-0.3V
to V
CCL
+ 0.5V
LDO Gate Drive (LDGD) Output Drive can source .................................................. 10mA
LDO Feedback (LDFB) Input.......................................................................................6.0V
Operating Junction Temperature................................................................................ 150°C
Operating Temperature Range.......................................................................-40°C to 85°C
Storage Temperature Range.........................................................................-65°C to 150°C
Peak Package Solder Reflow Temp. (40 seconds maximum exposure).........260°C (+0 -5)
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
.
Limitations affecting transient pulse duration is thermally related to the clamping zener
diodes connected to the supply pins, application of maximum voltage will increase current
into that pin and increase power dissipation.
x denotes respective pin designator 1, 2, or 3.
THERMAL DATA
LQ
Plastic MLPQ 38-Pin
THERMAL RESISTANCE-JUNCTION TO AMBIENT, θ
JA
30 to 55°C/W
Junction Temperature Calculation: T
J
= T
A
+ (P
D
x θ
JA
).
The θ
JA
numbers are dependent on heat spreading and layout considerations for the thermal
performance of the device/pc-board system. All of the above assume no ambient airflow.
PACKAGE PIN OUT
LO2
HR2
HO2
VC2
CS2
SF
EO2
SS2
RF2
EO1
FB1
SS3
FB3
EO3
FS
CS3
DGND
CS1
VIN
VCCL
PG3
LO3
HO3
VC3
VC1
HO1
HR1
LO1
PG1
LDGD
VSLR
SSL
LDFB
SS1
AGND
VREF
FB2
HR3
1
2
3
4
5
6
7
8
9
10
11
12
13 14 15 16 17 18 19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35363738
Connect Bottom to
Power GND
LQ PACKAGE
(Top View)
RoHS / Pb-free 100% Matte Tin Lead Finish
P
P
A
A
C
C
K
K
A
A
G
G
E
E
D
D
A
A
T
T
A
A
LX1675
PRODUCTION DATA SHEET
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 3
Copyright © 2004
Rev. 1.2a, 2006-02-16
WWW.Microsemi .COM
Multiple Output LoadSHARE™ PWM
TM
®
FUNCTIONAL PIN DESCRIPTION
Name Description
FB1
Bi-Phase Operation: Phase 1 and 2 Voltage Feedback
Single Phase Operation: Phase 1 Voltage Feedback, connect to the output through a resistor network to set desired
output voltage of Phase 1.
FB2
Bi-Phase Operation: Load Sharing Voltage Sense Feedback – Connect filtered phase 2 switching output (pre-inductor)
to FB2 to ensure proper current sharing between phase 1 and phase 2. Single Phase Operation: Phase 2 Voltage
Feedback, connect to the output through a resistor network to set desired output voltage of Phase 2.
FB3
Phase 3 Voltage Feedback , connect to the output through a resistor network to set desired output voltage of Phase 3.
RF2
Bi-Phase Operation: Load Sharing Voltage Sense Feedback Reference – Sets reference for current sharing control
loop. Connecting filtered phase 1 switching output (pre-inductor) to RF2 forces the average current in
phase 2 to be equal to phase 1. Single Phase Operation: Phase 2 Voltage Reference – connected to SS2 pin
as the reference.
EOX Error Amplifier Output – Sets external compensation for the corresponding phase denoted by “X”.
VIN Controller supply voltage.
VCCL
For 4.5V < VIN < 6V, this pin becomes the input voltage supply for the controller’s internal logic and gate drivers. For
VIN > 6V this pin is an output of the internal 5V regulator that supplies internal logic, Low Side Gate drivers and High
Side charge pump capacitor charging, if used. User must provide low ESR decoupling capacitor for pulse load currents
AGND Analog ground reference.
DGND Digital/Switching ground reference for current paths of the PWM driver circuits.
VSLR Supply pin for LDO regulator section.
LDFB Low Dropout Regulator Voltage Feedback – Sets the output voltage of external MOSFET via resistor network.
LDGD Low Dropout Regulator Gate Drive – Connects to gate of external N-MOSFET for linear regulator supply.
SSL
LDO Enable and Soft-start/Hiccup Capacitor Pin - During start-up, the voltage on this pin ramps from 0V to VREF
controlling the output voltage of the regulator. An internal 20k resistor connected to VREF and the external capacitor
set the time constant for soft-start function. The Soft-start function does not initialize until the supply voltage exceeds the
UVLO threshold.
SF
Shared Fault - If SF input = Logic 1(VCCL) and current limit threshold is reached during 4 clock cycles all outputs are
shutdown by discharging SS caps to zero and the start-up sequence begins again, this becomes hiccup mode protection
with the duty cycle set by the size of the SS capacitor. When operated in Bi-phase mode, SF must be set High. If SF =
logic 0, the other outputs continue to function normally and the faulted output enters the hiccup mode for current limit.
FS
Frequency Select Logic Input - Connect to ground for 300KHz and VCCL for 600KHz operation. Input has 100K Pull
down resistor.
VREF Buffered version of the internal 0.8 voltage reference.
CSX
Over-Current Limit Set – Connecting a resistor between CSX pin and the drain of the low-side MOSFET sets the current-
limit threshold for the corresponding phase denoted by “X”. A minimum of 500 must be in series with
this input. Whenever the current limit threshold is reached for 4 consecutive clock cycles the soft start capacitor is
discharged through an internal resistor initiating Soft Start and Hiccup mode.
SSX
Enable & Soft-start/Hiccup Capacitor Pin – During start-up, the voltage on this pin controls the output voltage of its
respective regulator. An internal 20k resistor and the external capacitor set the time constant for soft-start function.
The Soft-start function does not initialize until the supply voltage exceeds the UVLO threshold. When an over-current
condition occurs, this capacitor is used for the timing of hiccup mode protection. Pulling the SS pin below 0.1V disables
the corresponding phase denoted by “X”.
VCX
PWM High-Side MOSFET Gate Driver Supply – Connect to separate supply or to boot strap supply to ensure proper
high-side gate driver supply voltage. “X” denotes corresponding phase. If the phase is not used connect
to VCC.
HOX High Side MOSFET Gate Driver – “X” denotes corresponding phase.
LOX Low Side MOSFET Gate Driver – “X” denotes corresponding phase.
PGX
Low-side Driver Power Ground. Connects to the source of the bottom N-channel MOSFETS of each phase, where X
denotes corresponding phase. PG1 is the shared ground of PWM 1 and PWM 2 Low-side drivers.
HRX High Side driver return, connect this pin to High Side MOSFET source. “X” denotes corresponding phase.
P
P
A
A
C
C
K
K
A
A
G
G
E
E
D
D
A
A
T
T
A
A
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P19

LX1675CLQ-TR

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Manufacturer:
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IC REG QUAD BUCK/LNR SYNC 38MLPQ
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