LT1268 [Linear]
7.5A, 150kHz Switching Regulators; 7.5A , 150kHz的开关稳压器型号: | LT1268 |
厂家: | Linear |
描述: | 7.5A, 150kHz Switching Regulators |
文件: | 总4页 (文件大小:67K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
LT1268B/ LT1268
7.5A, 150kHz
Switc hing Re g ula to rs
U
DESCRIPTIO
EATURE
S
F
■
■
■
■
■
■
Wide Input Voltage Range: 3.5V to 30V
Low Quiescent Current: 7mA
Internal 7.5A Switch
Very Few External Parts Required
Self-Protected Against Overloads
Available in Standard and Surface Mount
5-Pin Packages
The LT1268B and LT1268 are monolithic high power
switching regulators. Identical to the popular LT1070,
except for switching frequency (150kHz) and higher
switch current, they can be operated in all standard
switching configurations including buck, boost, flyback,
and inverting. A high current, high efficiency switch is
included on the die along with all oscillator, control, and
protection circuitry. Integration of all functions allows
the LT1268 to be built in standard 5-pin power packages.
This makes it extremely easy to use and provides “bust
proof” operations similar to that obtained with 3-pin
linear regulators.
■
Can Be Externally Synchronized
(See LT1072 Data Sheet)
O U
PPLICATI
S
A
■
High Efficiency Boost Converter
PC Power Supply with Multiple Outputs
Battery Upconverter
■
■
■
The LT1268 operate with supply voltages from 3.5V to
30V and draw only 7mA quiescent current. By utilizing
current mode switching techniques, it provides excellent
AC and DC load and line regulation.
Negative-to-Positive Converter
USER NOTE:
This data sheet is only intended to provide specifications, graphs, and a general functional
description of the LT1268B/LT1268. Application circuits are included to show the capability of the
LT1268B/LT1268.Acompletedesignmanual(AN19)shouldbeobtainedtoassistindevelopingnew
designs. This manual contains a comprehensive discussion of both the LT1070 and the external
components used with it, as well as complete formulas for calculating the values of these
components. The manual can also be used for the LT1268B/LT1268 factoring in the higher switch
current rating and higher operating frequency.
TheLT1268useanadaptiveanti-satswitchdrivetoallow
verywiderangingloadcurrents withnoloss inefficiency.
An externally activated shutdown mode reduces total
supply current to 100µA typical for standby operation.
U
O
TYPICAL APPLICATI
Boost Regulator with 5.3V ±1% Output
Efficiency of 5.3V Boost Converter
D1
MBR1035
100
L1
8µH, 5A*
L2
2µH, 5A**
V
V
OUT
IN
4.7V TO
5.3V
5.3V ±1%
3.75A
V
= 5.3V
IN
D2, D3†
1N4001
90
80
70
60
C3
390µF
16V
+
V
IN
= 4.7V
C5
0.02
R1
4.043k
0.1%
V
IN
= 5V
V
V
SW
IN
LT1268B FB
CASE GND
C4
+
C1
220µF
16V
+
390µF
16V
V
C
R2
1.24k
0.1%
C2
0.068
R3
220Ω
2
LOAD CURRENT (A)
0
1
3
4
LT1268 • TA01
*COILTRONICS CTX8-5-52
**COILTRONICS CTX2-5-52
†OPTIONAL. D2 AND D3 ARE USED TO INCREASE
LT1268 • TA02
UNDERVOLTAGE LOCKOUT FROM 2.7V TO ≈4V.
1
LT1268B/ LT1268
W
U
W W W
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ABSOLUTE AXI U RATI GS
/O
PACKAGE RDER I FOR ATIO
Supply Voltage ....................................................... 30V
Switch Output Voltage ............................................ 60V
Feedback Pin Voltage (Transient, 1ms) ................ ±15V
Operating Junction Temperature Range
Operating............................................... 0°C to 125°C
Short-Circuit......................................... 0°C to 140°C
Storage Temperature Range ................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
FRONT VIEW
ORDER PART
5
4
3
2
1
V
IN
NUMBER
V
SW
GND
FB
V
C
LT1268CQ
LT1268BCQ
Q PACKAGE
5-LEAD DD
T
JMAX = 125°C, θJC = 2°C/W, θJA = See Notes 5 and 6
FRONT VIEW
ORDER PART
NUMBER
V
5
4
3
2
1
IN
V
SW
GND
FB
V
C
LT1268CT
LT1268BCT
T PACKAGE
5-LEAD TO-220
TJMAX = 125°C, θJC = 2°C/W, θJA = 50°C/W
Consult factory for Industrial and Military parts
ELECTRICAL CHARACTERISTICS V = 15V, V = 0.5V, VFB = VREF, switch pin open, unless otherwise noted.
IN
C
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
Reference Voltage Measured at
Feedback Pin (Note 4)
LT1268B
1.235
1.224
1.244
1.244
1.253
1.264
V
V
REF
●
●
●
●
●
Reference Voltage
LT1268
1.224
1.214
1.244
1.244
1.264
1.274
V
V
I
B
Feedback Input Current
V
FB
= V
REF
350
4400
200
750
1100
nA
nA
g
m
Error Amplifier Transconductance
Error Amplifier Source or Sink Current
Error Amplifier Clamp Voltage
∆I = ±25µA
C
3000
2400
6000
7000
µmho
µmho
V = 1.5V
C
150
120
350
400
µA
µA
Hi Clamp, V = 1V
Lo Clamp, V = 1.5V
1.80
0.25
2.30
0.52
V
V
FB
0.38
FB
Reference Voltage Line Regulation
Error Amplifier Voltage Gain
Minimum Input Voltage
Supply Current
3V ≤ V ≤ V , V = 0.8V
●
●
0.03
%/V
V/V
V
IN
MAX
C
A
0.9V ≤ V ≤ 1.4V
500
800
2.8
7
V
C
3.0
10
I
Q
3V ≤ V ≤ V , V = 0.6V
mA
IN
MAX
C
Control Pin Threshold
Duty Cycle = 0
0.7
0.5
0.9
1.08
1.25
V
V
●
●
BV
Output Switch Breakdown Voltage
3V ≤ V ≤ V , I = 1.5mA
60
75
V
IN
MAX SW
V
SAT
Output Switch-ON Resistance
(Note 1, 3)
T ≤ 100°C
T ≤ 125°C
J
0.12
0.18
0.22
Ω
Ω
J
Control Voltage to Switch
Current Transconductance
12
A/V
I
Switch Current Limit (Note 3, 6)
Duty Cycle = 50%, T ≤ 100°C
●
●
7.50
6.50
15
14
A
A
LIM
J
Duty Cycle = 65%, T ≤ 100°C
J
2
LT1268B/ LT1268
E
SYMBOL
LECTRICAL CHARACTERISTICS V = 15V, V = 0.5V, VFB = VREF, switch pin open, unless otherwise noted.
IN
C
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
∆I
Supply Current Increase
During Switch-ON Time
25
45
mA/A
IN
∆I
SW
f
Switching Frequency
120
120
150
180
180
kHz
kHz
●
DC
MAX
Maximum Switch Duty Cycle
65
85
92
%
Shutdown Mode Supply Current
Shutdown Mode Threshold Voltage
3V ≤ V ≤ V , V = 0.05V
100
150
500
µA
IN
MAX
C
3V ≤ V ≤ V
100
50
250
300
mV
mV
IN
MAX
●
The
●
denotes specifications which apply over the full operating
has a thermal resistance of 20°C/W to 50°C/W (see graph). The following
formula will allow an estimate of maximum continuous switch current as a
function of power loss and duty cycle. See AN19 for more details.
temperature range.
Note 1: Measured with V in hi clamp, V = 0.8V.
C
FB
Note 2: For duty cycles (DC) between 50% and 65%, minimum guaranteed
P
IMAX
=
switch current is given by I = 6.25 (1.7 – DC).
LIM
R
SW × DC
P = Power dissipation due to switch current
= Switch-ON resistance ≈0.15Ω
Note 3: Minimum current limit is reduced by 0.5A at 125°C. 100°C test
limits are guaranteed by correlation to 125°C tests.
R
SW
Note 4: LT1268B reference voltage is specified at ±9mV to guarantee ±1%
output voltage accuracy when 0.1% external resistors are used to set
output voltage. To maintain output accuracy under load, load current
should be taken from the case and the ground pin should be connected
separately to output ground. See AN19 for details.
DC = Switch duty cycle
In a typical application where thermal resistance is 30°C/W, maximum
power might be limited to 2W and power allocated to switch loss is 1.5W.
For a duty cycle of 40%, this yields
Note 5: The Q package is intended for surface mount without a separate
heat sink. See graph for thermal resistance as a function of the mounting
area. This curve assumes no other heat dissipators adjacent to package.
1.5
0.15 × 0.4
IMAX
=
= 5A
Obviously, a combination of high thermal resistance and high duty cycle
may restrict switch current to a value well below the 7.5A electrical limit.
Note 6: Maximum switch current may be limited by package power
dissipation, especially for the surface mount (Q) package. This package
W U
TYPICAL PERFOR A CE CHARACTERISTICS
Switch Current Limit vs Duty Cycle
Switch Saturation Voltage
Q Package Thermal Resistance
24
18
12
6
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
60
50
40
30
20
10
0
T = 25°C
J
SINGLE-SIDED BOARD, 1oz COPPER
–55°C
25°C
125°C
DOUBLE-SIDED BOARD, 1oz COPPER
BOTTOM COPPER AREA >100cm2
0
0
10
15
20
25
30
0
10 20 30 40 50 60 70 80 90 100
DUTY CYCLE (%)
0
1
2
3
4
5
6
7
8
9
10
5
TOP SURFACE COPPER AREA (cm2)
SWITCH CURRENT (A)
LT1268 • 603
LT1268 • TPC01
LT1268 • TPC02
InformationfurnishedbyLinearTechnologyCorporationis believedtobeaccurateandreliable.However,
no responsibility is assumed for its use. Linear Technology Corporation makes no representation that
the interconnection of its circuits as described herein will not infringe on existing patent rights.
3
LT1268B/ LT1268
U
O
TYPICAL APPLICATI
Boost Converter (5V TO 12V)
5V
20µH
V
IN
V
SW
MBR1020
12V, 1.5A
LT1268CT
10.7k
FB
+
1000µF
25V
GND
V
C
1k
1.24k
+
1µF
LT1268 • TA03
U
PACKAGE DESCRIPTIO
Dimensions in inches (millimeters) unless otherwise noted.
0.401 ± 0.015
(10.185 ± 0.381)
0.060
(1.524)
0.175 ± 0.008
0.050 ± 0.008
(4.445 ± 0.203)
(1.270 ± 0.203)
15° TYP
+0.008
0.004
+0.012
0.331
8.407
–0.004
0.059
(1.499)
TYP
–0.020
Q Package
5-Lead DD
+0.203
0.102
+0.305
–0.508
(
)
–0.102
(
)
0.105 ± 0.008
(2.667 ± 0.203)
0.067 ± 0.010
(1.702 ± 0.254)
0.050 ± 0.012
(1.270 ± 0.305)
+0.012
–0.020
0.022 ± 0.005
(0.559 ± 0.127)
0.143
0.032 ± 0.008
(0.813 ± 0.203)
+0.305
–0.508
3.632
(
)
0.380 – 0.420
(9.652 – 10.668)
0.169 – 0.185
(4.293 – 4.699)
0.079 – 0.135
(2.007 – 3.429)
0.035 – 0.055
(0.889 – 1.397)
0.139 – 0.153
(3.531 – 3.886)
DIA
0.560 – 0.650
T Package
5-Lead TO-220
0.460 – 0.500
(11.68 – 12.70)
(14.224 – 16.510)
0.620 ± 0.020
(15.75 ± 0.508)
0.866 – 0.913
(21.996 – 23.190)
0.700 – 0.728
(17.780 – 18.491)
0.970 – 1.050
(24.64 – 26.67)
0.055 – 0.090
(1.397 – 2.286)
0.079 – 0.115
(2.007 – 2.921)
0.015 – 0.025
(0.381 – 0.635)
0.210 – 0.240
(5.334 – 6.096)
0.057 – 0.077
(1.448 – 1.956)
0.149 – 0.230
(3.785 – 5.842)
0.028 – 0.035
(0.711 – 0.889)
0.304 – 0.380
(7.722 – 9.652)
1268fs, sn1268 LT/GP 0194 10K REV 0 • PRINTED IN THE USA
LINEAR TECHNOLOGY CORPORATION 1994
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7487
4
●
●
(408) 432-1900 FAX: (408) 434-0507 TELEX: 499-3977
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