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LX2172 / 73
1.25A HIGH-EFFICIENCY 100KHZ SWITCHING REGULATOR
T
HE
I
NFINITE
P
OWER
OF
I
NNOVATION
P
RELIMINARY
D
ATA
S
HEET
DESCRIPTION
KEY FEATURES
1.25A, 65V Internal Power Switch 3V - 25V Input Voltage Range Current-Mode Operation Improved Internal Cycle-ByCycle Current Limiting Thermal Shutdown Less Than 10A Quiescent Current In Microprocessor Shutdown Mode External Frequency Synchronization Possible 100kHz Operating Frequency
IMPORTANT: For the most current data, consult MICROSEMI's website: http://www.microsemi.com
SEPIC C ONVER TER U SING THE LX2172 Input 6-24V Output 7V 300mA , ,
VIN 6-24V DC C2 330 F
NO T R OB EC SO OM L ME ET ND E P ED RO FO R DU NE C WT DE SIG NS
PRODUCT HIGHLIGHT
L1 D1 Output 7V 300mA
The LX2172/73 are fixed-frequency, current-mode switching regulator integrated circuits. These ICs contain all necessary control circuitry plus a 1.25A on-board transistor to design a complete DC:DC switching regulator with minimum external components. All functions are integrated into a single IC, available in 8-pin DIP and SOIC or a 5pin TO-220 power package, making them extremely easy to design with and use. The LX2172/73 are optimized for
boost and flyback applications, but can also be used in forward and inverting converter configuations. The LX2172 can be connected to an external clock for synchronization, and can enter micropower operation when the VC pin is pulled low. The LX2173 has an enable function, which permits extremely low micropower operation, consuming under 10A current when the ENABLE pin is brought low
APPLICATIONS
Boost Converter Laptop / Notebook Computers Portable Equipment Small Motor Applications Flyback Converters
Part #
Pin 4 Connection SYNC Input Low Power Mode (Hi ENABLE)
7V
LX2172 LX2173
C1 22 F R1 13.7k C4 0.47 F
C3
1mH
1N5817
0.1 F
U1
1 2 3 4
GND VC
E2
8 7 6 5
COUT 220 F
VSW
FB
E1
SYNC
VIN
L2 1mH
(See Note 1)
CDECOUPLE 0.47 F
R2 3.0k
R3 100
Note 1: SYNC Pin Requirements: A) FMAX = 200kHz B) TTL Compatible Level s C) Pulse Width TP Range - 0.1 < TP < 2.0s
TA (C) 0 to 70
M
Plastic DIP 8-Pin
PACKAGE ORDER INFO Plastic SOIC DM 8-Pin
P
Plastic TO-220 5-Pin
RoHS Compliant / Pb-free Transition DC: 0503
RoHS Compliant / Pb-free Transition DC: 0440
LX217xCM
LX217xCDM
LX217xCP
Note: Available in Tape & Reel. Append the letters "TR" to the part number. (i.e. LX2172CDM-TR)
Copyright (c) 1998 Rev. 0.4a ,2005-03-09
LINFINITY MICROELECTRONICS INC.
11861 WESTERN AVENUE, GARDEN GROVE, CA. 92841, 714-898-8121, FAX: 714-893-2570
1
PRODUCT DATABOOK 1996/1997
LX2172/73
1.25A HIGH-EFFICIENCY 100KHZ SWITCHING REGULATOR
P
RELIMINARY
D
ATA
S
HEET PACKAGE PIN OUTS
GND VC FB * SYNC / ENABLE
1 2 3 4 8 7 6 5
A B S O L U T E M A X I M U M R AT I N G S
(Note 1)
NO T R OB EC SO OM L ME ET ND E P ED RO FO R DU NE C WT DE SIG NS
T H E R MAL DATA
95C/W 165C/W 4.5C/W 60C/W
Supply Voltage (VIN) .................................................................................................... 25V Collector Supply Voltage (VC ) ..................................................................................... 65V Digital Inputs (SYNC) ......................................................................................... -0.3 to 7V Operating Junction Temperature ................................................................. 0C to 125C Storage Temperature Range .................................................................... -65C to +150C Solder Temperature (Soldering, 10 seconds) .......................................................... 300C
E2 VSW E1 VIN
Pb-free / RoHS Peak Package Solder Reflow Temp (40 second max. exposure)................. 260C (+0, -5) Note 1. Exceeding these ratings could cause damage to the device. All voltages are with respect to Ground. Currents are positive into, negative out of the specified terminal.
RoHS / Pb-free 100% Matte Tin Lead Finish
1 2 3 4 8 7 6 5
M PACKAGE (Top View)
M PACKAGE: DM PACKAGE: P PACKAGE:
GND VC FB * SYNC / ENABLE
E2 VSW E1 VIN
THERMAL RESISTANCE-JUNCTION TO AMBIENT, JA THERMAL RESISTANCE-JUNCTION TO AMBIENT, JA THERMAL RESISTANCE-JUNCTION TO TAB, JT
DM PACKAGE (Top View)
* Pin 4 = SYNC for LX2172, ENABLE for LX2173/2174 RoHS / Pb-free 100% Matte Tin Lead Finish TAB IS GND
5
THERMAL RESISTANCE-JUNCTION TO AMBIENT, JA
Junction Temperature Calculation: TJ = TA + (PD x JA). The JA numbers are guidelines for the thermal performance of the device/pc-board system. All of the above assume no ambient airflow.
1
VIN VSW GND FB VC
P PACKAGE (Top View)
BLOCK DIAGRAM
V
IN
V
IN
V
IN
5
1 .4 V
ENABLE COMP
GND
V
1
(N O T E 1 )
EN
2 .3 V V REG
V
REG
UVLO
REG
COMP
ENABLE V
O
2 .3 V
7 S
W
0 .1 5 V
S .D . COMP
V
O
1 .2 7 V
E .A .
g
F
B
M
PW M COMP
PW M LATCH
Q1
Q2
3
R
Q
S
Q
V
C
2
V OFS (0 .9 V )
1 .4 V
0 .1 6 W
100kH z
250m V
EN
C .S . AMP
100 kH z OSC IN
SLO PE CO M P
(N O T E 1 ) SYNC
6 E1
Note 1: LX2172 Only: SYNC brought out to pin 4. ENABLE is tied to V IN. LX2173 Only: ENABLE brought out to pin 4. SYNC is open.
0 .1 6 W
8 E2
2
Copyright (c) 1998 Rev. 0.4a 12/04
PRODUCT DATABOOK 1996/1997
LX2172/73
1.25A HIGH-EFFICIENCY 100KHZ SWITCHING REGULATOR
P
RELIMINARY
D
ATA
S
HEET
ELECTRICAL CHARACTERISTICS
Parameter Reference Section
Initial Accuracy Line Regulation
NO T R OB EC SO OM L ME ET ND E P ED RO FO R DU NE C WT DE SIG NS
Symbol Test Conditions
(Unless otherwise specified, these specifications apply over the ranges TA = 0 to 70C for the LX217xC. VIN = VC = 5V. All devices must be functional over junction temperature of -65C to 150C. Typ. number represents TA = 25C value.)
LX2172 / 2173 Min. Typ. Max.
1.244 1.244 0.03 100 100 1.264 1.274
Units
VREF
TJ = 25C, Measured at FB pin Over Temperature, Measured at FB pin 3V < VCC < 25V TA = 25C Over Temperature VIN = 3V to 25V
1.224 1.214
V V %/V kHz kHz % nA nA V/V MHO MHO A A V V V/sec ns A/V
Oscillator Section
Switching Frequency Line Voltage Stability Input Bias Current Open Loop Gain Transconductance Output Sink Current Output Source Current Output HI Voltage Output LO Voltage Slew Rate
f
90 85
110 115 5 750 1100 1000 6000 7000
Error Amplifier Section
IB
TJ = 25C; VFB = VREF Over Temperature
350 500 4400 200 2.1 0.3 2 100 2 0.6 80 65 0.4 1.7 1.5 100 2.7 5 150 100 5 1.2 36 90
AVOL gm
TJ = 25C; VFB = V REF; I = 25A Over Temperature
IEA (SINK) I EA (SOURCE) VCOMP-HI VFB = 1V VCOMP-LO VFB = 1.5V S
3000 2400 120 120 1.8 0.2
2.3 0.52
C.S. Comparator Section
C.S. Delay to Driver Output VC to Output Transconductance
10% Over drive GBNT
PWM Section
E.A. Output to PWM Drive Offset (VPWM) Minimum Duty Cycle Maximum Duty Cycle
VOFS
Duty Cycle = 0
1.25 40 98
V % % V A A mW V mA mV mV A A
Output Drive Section
Output Switch Breakdown Voltage Output Switch On Resistance Switch Current Limit
RON ILIM
Total Switching Loss (On Time + Off Time)
ISW = 1.5mA IO = 2A D.C = 50% 50% < D.C < 80% VIN = 25V, D.C = 50%, IO = 1A, VSW = 60V
1.25 1.0
0.6 2.8 2.0
Input Supply Section
Start-Up Threshold Normal Mode Quiescent Current VC Shutdown Threshold Sleep Mode Current
2.2
IQ
ENABLE = HI, VC = 0.6V, IO = 0A 3V < VIN < VMAX , TJ = 25C 3V < VIN < VMAX , Over Temperature ENABLE = HI, VC = 50mV ENABLE = LO (LX2173 only)
100 50
2.9 8 260 300
Copyright (c) 1998 Rev. 0.4a 12/04
3
PRODUCT DATABOOK 1996/1997
LX2172/73
1.25A HIGH-EFFICIENCY 100KHZ SWITCHING REGULATOR
P
RELIMINARY
D
ATA
S
HEET
ELECTRICAL CHARACTERISTICS
SYNC Input Section (LX2172 only)
SYNC Pulse Width SYNC Input HI SYNC Input LO SYNC Input Current HI SYNC Input Current LO Enable Input Threshold HI Input Current LO Input Current
NO T R OB EC SO OM L ME ET ND E P ED RO FO R DU NE C WT DE SIG NS
Parameter
Symbol
Test Conditions
LX2172 / 2173 Min. Typ. Max.
0.2 2 100 1 0.4 1.2 2 6 0.7 400 5 2.4 200 100
Units
Input = 2V Input = 0.4V
sec V V A A V A A
ENABLE Section (LX2173 only)
Input = 2.4V Input = 0.4V
FUNCTIONAL PIN DESCRIPTION
Pin Name
GND VC
Pin #
1 2
Pin #
3
(8-pin Pkgs.) (5-pin TO-220)
Description
Signal ground. Keep separate from power grounds (E1 and E2).
1
Output of transconductance error amplifier. An R-C compensation network is connected from this pin to the ground to stabilize the feedback loop. If this pin is pulled lower than 0.15V, the IC goes into micropower mode. Error amplifier inverting input. A resistor divider from the output of the converter to this pin sets its nominal voltage. LX2172 only. This pin is used to synchronize the device directly with a logic level input pulse. External synchronization frequency must always be at a higher frequency than the minimum internal clock. When not used, should be left open. LX2173 only. This pin is the input to the enable comparator. A voltage under 1.4V will put the device in micropower mode. Pin must be connected to VIN when not in use.
FB SYNC
3 4
2
ENABLE VIN E1 VSW E2
4 5 6 7 8
5
Input supply voltage (3.0V to 25V).
Power return of first transistor (Q1). This pin must be connected to ground. Collector of output transistors. Connect to external inductor or input voltage, depending on circuit topology. Grounding this pin sets the current limit point to the maximum value. If pin is left open, the current limit is set to half its maximum value.
4
4
Copyright (c) 1998 Rev. 0.4a 12/04
PRODUCT DATABOOK 1996/1997
LX2172/73
1.25A HIGH-EFFICIENCY 100KHZ SWITCHING REGULATOR
P
RELIMINARY
D
ATA
S
HEET
T H E O R Y O F O P E R AT I O N
Referring to the block diagram, when VIN is above the UVLO start threshold the 2.3V UVLO comparator output switches to low state, allowing Q1 to turn on upon receiving a clock pulse from the internal 100kHz oscillator. Once Q1 is on, current in the inductor ramps up. Inductor current is then sensed, and amplified by a current sense amplifier and compared to a threshold set by the output of the error amplifier minus the offset voltage (VOFS typically 0.9V). This allows the PWM comparator to reset the flip flop, causing Q1 to turn off. The oscillator then sets the flip flop, and the operation repeats itself. CURRENT LIMIT
Current limiting is performed by sensing the peak switch current and turning Q1 off until the next clock cycle. When the converter goes into current limit the error amplifier output goes to the rail and sets a maximum limit on the current. ERROR AMPLIFIER
The function of the error amplifier is to set a threshold voltage for inductor peak current and control the switch duty cycle so that the power supply output voltage is closely regulated. Regulation is accomplished by sensing the output voltage and comparing it to the internal 1.27V bandgap reference. A compensation network is placed from the output of the amplifier to ground for closed loop stability purposes, as well as a high d.c. gain for tight regulation. The function of V OFS is to keep Q1 off without requiring an error amplifier output to swing to ground level. It is required the VOL of the error amplifier is always less than the offset at all times. The transfer function between the error amplifier output (VC ) and peak inductor current is therefore given by: VC - V OFS = I P * G * R S
Where: IP = Inductor peak current G = Current sense gain (typically 6) R S = Internal sense resistor
Copyright (c) 1998 Rev. 0.4a 12/04
NO T R OB EC SO OM L ME ET ND E P ED RO FO R DU NE C WT DE SIG NS
UNDER-VOLTAGE LOCKOUT EXTRA PINS ON 8-PIN DEVICE MICROPOWER SHUTDOWN
IC OPERATION
OSCILLATOR
The oscillator is designed to operate at 100kHz frequency. Its function is to turn the switch Q1 on at a fixed 10s interval and to provide a slope compensation for the feedback loop. Slope compensation is required for fixed frequency continuous Current Mode regulators operating above 50% duty cycle in order to prevent loop instability. The SYNC input is a logic input that allows easy synchronization to an external clock. Synchronization is done such that the external clock terminates the cycle before the internal oscillator sets the PWM latch again.
The 2.3V internal regulator is monitored as the input supply ramps up, ensuring glitch-free operation.
The 8-pin versions of the LX217x have the emitters of the power transistors brought out separately. Connecting these pins to ground reduces errors due to ground pin voltage drops. The E2 pin also allows the user to half the switch current limit if the pin is left open. Note that the switch resistance will increase when E2 is open, so efficiency will decrease and heat dissipation will increase, especially for currents over 300mA.
The LX2172/73 enter micropower shutdown mode when the VC pin is pulled below 0.15V. Supply current required for biassing shutdown circuitry is less than 250A. The LX2173 has an ENABLE pin which allows ultra-low micropower shutdown operation, consuming less than 10A.
5
PRODUCT DATABOOK 1996/1997
LX2172/73
1.25A HIGH-EFFICIENCY 100KHZ SWITCHING REGULATOR
P
RELIMINARY
D
ATA
S
HEET
T H E O R Y O F O P E R AT I O N
VOUT
NO T R OB EC SO OM L ME ET ND E P ED RO FO R DU NE C WT DE SIG NS
22F 180H
1
VIN +3V to +12V
GND VC FB
E2
8
2
14.7k
LX2172
VSW E1
7
1N5817
VOUT +16V
3
6
1.27
0.03F
4
SYNC
VIN
5
VIN
100
VIN
FIGURE 1 -- Boost Coverter Circuit Using The LX2172 / 2173
PRELIMINARY DATA - Information contained in this document is pre-production data, and is proprietary to Linfinity. It may not modified in any way without the express written consent of Linfinity. Product referred to herein is offered in sample form only, and Linfinity reserves the right to change or discontinue this proposed product at any time.
6
Copyright (c) 1998 Rev. 0.4a 12/04

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