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PDF LTC1530IS8-2.5 Data sheet ( Hoja de datos )
| Número de pieza | LTC1530IS8-2.5 | |
| Descripción | High Power Synchronous Switching Regulator Controller | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LTC1530
High Power Synchronous
Switching Regulator Controller
FEATURES
s High Power Buck Converter from 5V or 3.3V
Main Power
s Adjustable Current Limit in S0-8 with
Topside FET RDS(ON) Sensing
s No External Sense Resistor Required
s Hiccup Mode Current Limit Protection
s Adjustable, Fixed 1.9V, 2.5V, 2.8V and 3.3V Output
s All N-Channel MOSFET Synchronous Driver
s Excellent Output Regulation: ±2% over Line, Load
and Temperature Variations
s High Efficiency: Over 95% Possible
s Fast Transient Response
s Fixed 300kHz Frequency Operation
s Internal Soft-Start Circuit
s Quiescent Current: 1mA, 45µA in Shutdown
U
APPLICATIO S
s Power Supply for Pentium® II, AMD-K6®-2, SPARC,
ALPHA and PA-RISC Microprocessors
s High Power 5V to 1.3V-3.5V Regulators
DESCRIPTIO
The LTC®1530 is a high power synchronous switching
regulator controller optimized for 5V to 1.3V-3.5V output
applications. Its synchronous switching architecture drives
two external N-channel MOSFET devices to provide high
efficiency. The LTC1530 contains a precision trimmed
reference and feedback system that provides worst-case
output voltage regulation of ±2% over temperature, load
current and line voltage shifts. Current limit circuitry
senses the output current through the on-resistance of
the topside N-channel MOSFET, providing an adjustable
current limit without requiring an external low value sense
resistor.
The LTC1530 includes a fixed frequency PWM oscillator
that free runs at 300kHz, providing greater than 90%
efficiency in converter designs from 1A to 20A of output
current. Shutdown mode drops the LTC1530 supply cur-
rent to 45µA.
The LTC1530 is specified for commercial and industrial
temperature ranges and is available in the S0-8 package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Pentium is a registered trademark of Intel Corp.
AMD-K6 is a registered trademark of Advanced Micro Devices, Inc.
TYPICAL APPLICATIO
VIN
5V
MBR0530T1 MBR0530T1
0.1µF +
2.7k 10µF
+ CIN**
1200µF
0.22µF
×4
IMAX PVCC
G1
COMP
IFB
C1
150pF
RC
10k
LTC1530-3.3
G2
CC
0.022µF
GND VOUT
20Ω
Q1* LO†
2µH
Q2*
+
CO††
330µF
×7
VOUT
3.3V
14A
1530 F01a
† COILTRONICS CTX02-13198
OR PANASONIC ETQP6F2R5HA
†† AVX TPSE337M006R0100
* SILICONIX SUD50N03-10
** SANYO 10MV1200GX
COILTRONICS (561) 241-7876
Figure 1. Single 5V to 3.3V Supply
Efficiency vs Load Current
100
90
80
70
60
50
40
30
20
10
0
0
0.3
2
TA = 25°C
4 6 8 10 12 14
LOAD CURRENT (A)
1530 F01b
1
1 page  
TYPICAL PERFOR A CE CHARACTERISTICS
LTC1530
Error Amplifier Open-Loop Gain
vs Temperature
60
55
50
45
40
–55 –35 –15 5 25 45 65 85 105 125
TEMPERATURE (°C)
1530 G10
IMAX Sink Current vs Temperature
300
280
PVCC = 12V
G1, G2 ARE NOT SWITCHING
260
240
220
200
180
160
140
120
–55 –35 –15 5 25 45 65 85 105 125
TEMPERATURE (°C)
1530 G13
Shutdown Threshold Voltage
vs Temperature
250
PVCC = 12V
MEASURED AT
200 COMP PIN
150
100
50
0
–55 –35 –15 5 25 45 65 85 105 125
TEMPERATURE (°C)
1530 G16
Oscillator Frequency
vs Temperature
350
340
330
320
310
300
290
280
270
260
250
–55 –35 –15 5 25 45 65 85 105 125
TEMPERATURE (°C)
1530 G11
PVCC Supply Current
vs Gate Capacitance
70
PVCC = 12V
60
TA = 25°C
GATE CAPACITANCE = CG1 = CG2
50
40
30
20
10
0
012 345 67 8
GATE CAPACITANCE (nF)
1530 G14
Maximum G1 Duty Cycle
vs Ambient Temperature
92
PVCC = 12V
90 fOSC = 300kHz
88 G1, G2
CAPACITANCE
86 = 1000pF 2200pF
84
3300pF
82 5500pF
7700pF
80
THERMAL SHUTDOWN OCCURS
BEYOND THESE POINTS
78
–55 –35 –15 5 25 45 65 85 105 125
AMBIENT TEMPERATURE (°C)
1530 G12
PVCC Shutdown Supply Current
vs Temperature
80
75 PVCC = 12V
70
65
60
55
50
45
40
35
30
–55 –35 –15 5 25 45 65 85 105 125
TEMPERATURE (°C)
1530 G15
Output Overcurrent Protection
3.0
Transient Response
2.5
PVCC = 12V
TA = 25°C
2.0 REFER TO
FIGURE 2
1.5
1.0
SHORT-CIRCUIT
0.5 CURRENT
50mV/DIV
2A/DIV
0
0 1 2 3 4 5 6 7 8 9 10
OUTPUT CURRENT (A)
1530 G17
50µs/DIV
1530 G18
5
5 Page 
LTC1530
APPLICATIO S I FOR ATIO
OPTIONAL FOR
VIN > 6.5V
13V
1N5243B
+
10µF
MBR0530T1 MBR0530T1 VIN
PVCC
0.22µF
+
CIN
LTC1530
G1
G2
Q1
LO
+
Q2
VOUT
CO
1530 F07
Figure 7. Doubling Charge Pump
Power MOSFETs
Two N-channel power MOSFETs are required for synchro-
nous LTC1530 circuits. They should be selected based
primarily on threshold voltage and on-resistance consid-
erations. Thermal dissipation is often a secondary con-
cern in high efficiency designs. The required MOSFET
threshold should be determined based on the available
power supply voltages and/or the complexity of the gate
drive charge pump scheme. In 5V input designs where a
12V supply is used to power PVCC, standard MOSFETs
with RDS(ON) specified at VGS = 5V or 6V can be used with
good results. The current drawn from the 12V supply
varies with the MOSFETs used and the LTC1530’s operat-
ing frequency, but is generally less than 50mA.
LTC1530 applications that use a 5V VIN voltage and a
doubling charge pump to generate PVCC do not provide
enough gate drive voltage to fully enhance standard
power MOSFETs. Under this condition, the effective
MOSFET RDS(ON) may be quite high, raising the dissipa-
tion in the FETs and reducing efficiency. In addition,
power supply start-up problems can occur with standard
power MOSFETs. These start-up problems can occur for
two reasons. First, if the MOSFET is not fully enhanced,
the higher effective RDS(ON) causes the LTC1530 to acti-
vate current limit at a much lower level than the desired
trip point. Second, standard MOSFETs have higher GATE
threshold voltages than logic level MOSFETs, thereby
increasing the PVCC voltage required to turn them on. A
MOSFET whose RDS(ON) is rated at VGS = 4.5V does not
necessarily have a logic level MOSFET GATE threshold
voltage. Logic level FETs are the recommended choice for
5V-only systems. Logic level FETs can be fully enhanced
with a doubler charge pump and will operate at maximum
efficiency. Note that doubler charge pump designs run-
ning from supplies higher than 6.5V should include a
Zener diode clamp at PVCC to prevent transients from
exceeding the absolute maximum rating of the pin.
After the MOSFET threshold voltage is selected, choose
the RDS(ON) based on the input voltage, the output voltage,
allowable power dissipation and maximum output cur-
rent. In a typical LTC1530 buck converter circuit, operat-
ing in continuous mode, the average inductor current is
equal to the output load current. This current flows through
either Q1 or Q2 with the power dissipation split up accord-
ing to the duty cycle:
DC(Q1) = VOUT
VIN
( )DC(Q2) = 1− VOUT = VIN − VOUT
VIN VIN
The RDS(ON) required for a given conduction loss can now
be calculated by rearranging the relation P = I2R.
[ ]RDS(ON)Q1 =
PMAX(Q1)
DC(Q1)
IMAX2
( )[ ]VIN PMAX(Q1)
=
( )VOUT
IMAX2
[ ]RDS(ON)Q2 =
PMAX(Q2)
DC
(Q2)
IMAX2
( )[ ]VIN PMAX(Q2)
=
( )VIN
−
VOUT
IMAX2
11
11 Page | ||
| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet LTC1530IS8-2.5.PDF ] | |
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