lx1684 Microsemi Corporation, lx1684 Datasheet

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lx1684

Manufacturer Part Number
lx1684
Description
Voltage-mode Pwm Controller
Manufacturer
Microsemi Corporation
Datasheet
Copyright © 2000
Rev. 1.0c, 2005-03-08
mode pulse-width modulator controller.
It is designed to implement a flexible,
low cost buck (step-down) regulator
supply with a minimal of external
components.
driver for higher efficiency and is
optimized to provide 12V to 3.3V or
12V to 2.5V regulation. It also can be
used to convert 5V or 3.3V to voltages
as low as 1.25V.
175kHz for optimal cost and space.
Short-circuit current limiting can be
implemented without expensive current
sense resistors.
with the positive side of the current
sense comparator brought out (CSP) to
allow it to be referenced to the topside
FET.
IMPORTANT: For the most current data, consult MICROSEMI’s website: http://www.microsemi.com
The LX1684 is a monolithic, voltage-
The LX1684 has a synchronous
Switching frequency is fixed at
Similar to the LX1682 in function but
Optional 12V only circuit
TM
or equivalent
LM78L05
12V
P R O D U C T H I G H L I G H T - T Y P I C A L 1 2 V T O 3 . 3 V A P P L I C A T I O N
TO
VCC
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
5V
T
0 to 70
Note: Available in Tape & Reel. Append the letters “TR” to the part number. (i.e. LX1684CD-TR)
100 Ohm
165 Ohm
A
(°C)
R2
R1
D E S C R I P T I O N
0.1µF
Css
drop across the R
this sensing is delayed for 1µs to
eliminate
Hiccup-mode fault protection reduces
average power to the power elements
during short-circuit conditions.
are
performance. Pulling the soft-start pin to
ground can disable the LX1684.
combined with low profile, low ESR
capacitors, and TO-252 packaged FETs
results in a high efficiency converter in a
small board area. In most cases PCB
copper can accomplish necessary heat
sinking and no bulky additional heat
sinks are required.
small electrolytic capacitors can be used
reducing the overall converter cost.
Current is sensed using the voltage
Under-voltage lockout and soft-start
If a low profile design is not required
Synchronous
P A C K A G E O R D E R I N F O
The small 14-pin SOIC packaging,
Integrated Products Division
provided
O
1
2
3
4
5
6
7
UTPUT
®
Microsemi
FB
NC
SS
CSP
GND
PGND
BDR
MOSFET
for
DS(ON)
VCC
TDR
VC1
NC
NC
NC
CS
optimal
5V
5%
14
13
12
11
10
RoHS Compliant / Pb-free Transition DC: 0440
of the MOSFET
9
8
ringing
D
RSET
Voltage-Mode PWM Controller
3.3K
1µF
Plastic SOIC
14-PIN
C5
P
start-up
errors.
RODUCTION
5817SMT
LX1684CD
SUB45N
SUB45N05-
05-20L
0.1µF
D1
Q1
C1
20L
Q2
L1 is a powdered
D
iron toroid
10µH
ATA
12V to 3.3V Or Less Buck
Regulators
3.3/5V to 2.5V Or Less Buck
Regulators
Hard Disk Drives
Computer Add-on Cards
Fixed 175kHz Switching
Frequency
Constant Frequency Voltage-
Mode Control Requires No
External Compensation
Hiccup-Mode Over-Current
Protection
High Efficiency
Output Voltage Set By
Resistor Divider
Under-Voltage Lockout
Soft-Start And Enable
Synchronous Rectification
Small, 14-pin Surface Mount
Package
12V
10%
L1
K E Y F E A T U R E S
A P P L I C A T I O N S
820µF,
16V
S
3x
HEET
1500µF
6.3V
4x
C4
C3
VOUT
3.3V
10A
LX1684
Page 1

Related parts for lx1684

lx1684 Summary of contents

Page 1

... Ohm Optional 12V only circuit T (° Note: Available in Tape & Reel. Append the letters “TR” to the part number. (i.e. LX1684CD-TR) Copyright © 2000 Rev. 1.0c, 2005-03-08 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Voltage-Mode PWM Controller ® ...

Page 2

... θ ESCRIPTION Microsemi Integrated Products Division LX1684 RODUCTION ATA HEET N ...

Page 3

... V VC1 > 0.3V ; outputs low (disable) VCC SS Microsemi Integrated Products Division LX1684 D S RODUCTION ATA HEET ≤ ≤ T 70°C except where A LX1684 Min Typ Max 1.237 1.25 1.262 1.231 1.269 135 175 200 1. 300 380 420 1.0 50 ...

Page 4

... Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Voltage-Mode PWM Controller ® P RODUCTION SET UVLO Ramp UVLO O scillator Microsemi Integrated Products Division LX1684 D S ATA HEET I SET V (+12V) +17. ...

Page 5

... The internal oscillator and ramp generator frequency is fixed at 175kHz. The devices have internal compensation, so that no external compensation is required. POWER UP AND INITIALIZATION At power up, the LX1684 monitors the supply voltage to both the +5V and the V pins (there is no special requirement for the C1 sequence of the two supplies) ...

Page 6

... The required inductor current for the output capacitor to follow the SS-pin voltage equals the required capacitor current plus the load current. The soft-start capacitor should be selected so that the overall inductor current does not exceed its maximum. Microsemi Integrated Products Division LX1684 RODUCTION ATA HEET ...

Page 7

... Rev. 1.0c, 2005-03-08 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Voltage-Mode PWM Controller ® OUTPUT ENABLE The LX1684 FET driver outputs are driven to ground by pulling the soft-start pin below 0.3V − ...

Page 8

... The use of a dual Schottky diode in a single TO-220 package (e.g. the MBR2535) helps improve thermal dissipation. Boost Operation The LX1684 needs a secondary supply voltage (V sufficient drive to the upper MOSFET. The top FET must be a logic level power MOSFET such as SUB45N03-13L ...

Page 9

... CSP GND VC1 6 9 PGND BDR TDR – Figure 4 3.3V to 1.25V with Charge Pump. Microsemi Integrated Products Division LX1684 D S RODUCTION ATA HEET 2x 820µF, 16V Q1 L1 VOUT 10µ powder 4x iron Toroid 1500 MBR2545 µF 3.3V 10% C1 0.1µF 2x 150µ ...

Page 10

... DIV 2V / DIV OUTPUT VOLTAGE VS. TEMPERATURE 100mV / DIV Microsemi Integrated Products Division LX1684 RODUCTION ATA HEET OUTPUT VOLTAGE VS. LOAD Output Current (A) OUTPUT STARTUP V = 3.3V OUT 1ms / DIV I = 10A OUT 10µ ...

Page 11

... MIN MAX MIN A 8.54 8.74 0.336 B 3.81 3.94 0.150 C 1.35 1.75 0.053 D 0.33 0.51 0.013 F 0.77 G 1.27 BSC 0.050 BSC J 0.19 0.25 0.007 K 0.10 0.25 0.004 L 4.82 5.21 0.189 5.79 6.20 0.228 *LC 0.10 *Lead Coplanarity Microsemi Integrated Products Division LX1684 D S RODUCTION ATA HEET L J MAX 0.344 0.155 0.069 0.020 0.030 0.010 0.010 0.205 8 0.244 0.004 Page 11 ...

Page 12

... Microsemi reserves the right to change the configuration and performance of the product and to discontinue product at any time. Copyright © 2000 Rev. 1.0c, 2005-03-08 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Voltage-Mode PWM Controller ® P RODUCTION Microsemi Integrated Products Division LX1684 D S ATA HEET Page 12 ...

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