LT1614CS8 [Linear]
Inverting 600kHz Switching Regulator; 倒相600kHz的开关稳压器
| 型号： | LT1614CS8 |
| 厂家： | 
Linear |
| 描述： | Inverting 600kHz Switching Regulator |
| 文件： | 总8页 (文件大小：221K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Final Electrical Specifications
LT1614
Inverting 600kHz
Switching Regulator
July 1998
U
DESCRIPTION
FEATURES
The LT®1614 is a fixed frequency, inverting mode switch-
ing reglator that operates from an input voltage as low as
1V. Utilizing a low noise topology, the LT1614 can gener-
ate a negative output down to –24V from a 1V to 5V input.
Fixed frequency switching ensures a clean output free
from low frequency noise. The device contains a low-
battery detector with a 200mV reference and shuts down
tolessthan10µA.NoloadquiescentcurrentoftheLT1614
is 1mA and the internal NPN power switch handles a
500mA current with a voltage drop of just 295mV.
■
Better Regulation Than a Charge Pump
■
0.1Ω Effective Output Impedance
■
■
■
■
■
■
■
–5V at 200mA from a 5V Input
600kHz Fixed Frequency Operation
Operates with VIN as Low as 1V
1mA Quiescent Current
Low Shutdown Current: 10µA
Low-Battery Detector
Low VCESAT Switch: 295mV at 500mA
U
APPLICATIONS
High frequency switching enables the use of small induc-
tors and capacitors. Ceramic capacitors can be used in
many applications, eliminating the need for bulky tanta-
lum types.
■
MR Head Bias
■
LCD Bias
■
GaAs FET Bias
Positive-to-Negative Conversion
■
The LT1614 is available in 8-lead MSOP or SO packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
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TYPICAL APPLICATION
5V to –5V Converter
5V to –5V Converter Efficiency
C3
1µF
90
L1
22µH
L2
22µH
V
IN
5V
80
70
60
50
40
V
OUT
V
SW
IN
–5V
+
SHDN
LT1614
C1
200mA
69.8k
24.9k
33µF
C2
33µF
D1
V
C
NFB
+
GND
100k
1nF
1614 TA01
C1, C2: AVX TAJB336M010
C3: AVX 1206CY106
D1: MBR0520
3
10
30
100
300
L1, L2: MURATA LQH3C220
LOAD CURRENT (mA)
1614 TA02
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.
1
LT1614
W W W
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ABSOLUTE AXI U RATI GS
VIN, SHDN, LBO Voltage ......................................... 12V
SW Voltage ............................................... –0.4V to 30V
NFB Voltage ............................................................ –3V
VC Voltage ................................................................ 2V
LBI Voltage ............................................ 0V ≤ VLBI ≤ 1V
Current into FB Pin .............................................. ±1mA
Junction Temperature...........................................125°C
Operating Temperature Range
LT1614C................................................. 0°C to 70°C
LT1614I ............................................. –40°C to 85°C
Extended Commercial
Temperature Range (Note 1) .................. –40°C to 85°C
Storage Temperature Range ................ –65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
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/O
PACKAGE RDER I FOR ATIO
ORDER PART
NUMBER
ORDER PART
NUMBER
TOP VIEW
TOP VIEW
LT1614CS8
LT1614CMS8
NFB
1
2
3
4
8
7
6
5
LBO
LBI
NFB
1
2
3
4
8 LBO
7 LBI
LT1614IS8
V
C
V
C
6 V
SHDN
GND
IN
5 SW
SHDN
GND
V
IN
MS8 PACKAGE
8-LEAD PLASTIC MSOP
SW
S8 PART MARKING
MS8 PART MARKING
LTEJ
S8 PACKAGE
8-LEAD PLASTIC SO
TJMAX = 125°C, θJA = 160°C/W
1614
1614I
TJMAX = 125°C, θJA = 120°C/W
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
Commercial Grade 0°C to 70°C. VIN = 1.5V, VSHDN = VIN, TA = 25°C unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Quiescent Current
1
5
2
10
mA
µA
V
= 0V
SHDN
Feedback Voltage
●
●
–1.21
–2.5
–1.24
–4.5
–1.27
–7
V
NFB Pin Bias Current (Note 2)
Reference Line Regulation
V
= –1.24V
µA
NFB
1V ≤ V ≤ 2V
2V ≤ V ≤ 6V
0.6
0.3
1.1
0.8
%/V
%/V
IN
IN
Minimum Input Voltage
Maximum Input Voltage
Error Amp Transconductance
Error Amp Voltage Gain
Switching Frequency
0.92
1
6
V
V
●
∆I = 5µA
16
µmhos
V/V
100
600
●
●
500
750
kHz
Maximum Duty Cycle
73
70
80
80
%
%
Switch Current Limit (Note 3)
0.75
1.2
A
2
LT1614
ELECTRICAL CHARACTERISTICS
Commercial Grade 0°C to 70°C. VIN = 1.5V, VSHDN = VIN, TA = 25°C unless otherwise noted.
PARAMETER
Switch V
CONDITIONS
MIN
TYP
MAX
UNITS
I
I
= 500mA (25°C, 0°C)
= 500mA (70°C)
295
350
400
mV
mV
CESAT
SW
SW
Shutdown Pin Current
LBI Threshold Voltage
V
SHDN
V
SHDN
= V
= 0V
10
–5
20
–10
µA
µA
IN
190
185
200
210
215
mV
mV
●
LBO Output Low
I
= 10µA
0.1
0.01
10
0.25
0.1
50
V
µA
SINK
LBO Leakage Current
V
V
= 250mV, V
= 5V
LBO
LBI
LBI Input Bias Current (Note 4)
Low-Battery Detector Gain
Switch Leakage Current
= 150mV
nA
LBI
1MΩ Load
= 5V
1000
0.01
V/V
µA
V
3
SW
Industrial Grade –40°C to 85°C. VIN = 1.5V, VSHDN = VIN unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Quiescent Current
1
5
2
10
mA
µA
V
= 0V
SHDN
Feedback Voltage
●
●
–1.21
–2
–1.24
–4.5
–1.27
–7.5
V
NFB Pin Bias Current (Note 2)
Reference Line Regulation
V
= –1.24V
µA
NFB
1V ≤ V ≤ 2V
2V ≤ V ≤ 6V
0.6
0.3
1.1
0.8
%/V
%/V
IN
IN
Minimum Input Voltage
–40°C
85°C
1.1
0.8
1.25
1.0
V
V
Maximum Input Voltage
Error Amp Transconductance
Error Amp Voltage Gain
Switching Frequency
●
6
V
µmhos
V/V
∆I = 5µA
16
100
600
80
●
●
500
70
750
kHz
Maximum Duty Cycle
%
Switch Current Limit (Note 3)
0.75
1.2
A
Switch V
I
I
= 500mA (–40°C)
= 500mA (85°C)
250
330
350
400
mV
mV
CESAT
SW
SW
Shutdown Pin Current
V
V
= V
= 0V
10
–5
20
–10
µA
µA
SHDN
SHDN
IN
LBI Threshold Voltage
LBO Output Low
●
180
200
0.1
220
0.25
0.3
mV
V
I
= 10µA
SINK
LBO Leakage Current
V
V
= 250mV, V
= 5V
LBO
0.1
µA
nA
V/V
µA
LBI
LBI
LBI Input Bias Current (Note 4)
Low-Battery Detector Gain
Switch Leakage Current
= 150mV
5
30
1MΩ Load
= 5V
1000
0.01
V
3
SW
The
●
denotes specifications which apply over the full operating
Note 2: Bias current flows out of NFB pin.
temperature range.
Note 3: Switch current limit guaranteed by design and/or correlation to
Note 1: The LT1614C is guaranteed to meet specified performance from
0°C to 70°C and is designed, characterized and expected to meet these
extended temperature limits, but is not tested at –40°C and 85°C. The
LT1614I is guaranteed to meet the extended temperature limits.
static tests. Duty cycle affects current limit due to ramp generator.
Note 4: Bias current flows out of LBI pin.
3
LT1614
U
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PIN FUNCTIONS
NFB(Pin1):NegativeFeedbackPin. Referencevoltageis
–1.24V. Connect resistive divider tap here. The sug-
gested value for R2 is 24.9k. Set R1 and R2 according to:
GND (Pin 4): Ground. Connect directly to local ground
plane.
SW (Pin 5): Switch Pin. Minimize trace area at this pin to
keep EMI down.
| VOUT | –1.24
R1=
VIN (Pin 6): Supply Pin. Must have 1µF ceramic bypass
capacitor right at the pin, connected directly to ground.
1.24
+ 4.5 •10–6
R2
LBI (Pin 7): Low-Battery Detector Input. 200mV refer-
ence. Voltage on LBI must stay between ground and
700mV. Float this pin if not used.
VC (Pin 2): Compensation Pin for Error Amplifier. Con-
nect a series RC from this pin to ground. Typical values
are 100kΩ and 1nF. Minimize trace area at VC.
LBO (Pin 8): Low-Battery Detector Output. Open collec-
tor,cansink10µA.A1MΩpull-upisrecommended.Float
this pin if not used.
SHDN (Pin 3): Shutdown. Ground this pin to turn off
switcher. MustbetiedtoVIN (orhighervoltage)toenable
switcher. Do not float the SHDN pin.
W
BLOCK DIAGRAM
V
IN
6
V
IN
+
–
R5
40k
R6
40k
SHDN
V
C
SHUTDOWN
3
g
m
2
LBI
7
ERROR
AMPLIFIER
+
–
+
–
LBO
8
Q1
Q2
ENABLE
200mV
×10
BIAS
R3
30k
A4
A1
R4
140k
SW
5
COMPARATOR
–
+
1
DRIVER
FF
RAMP
NFB
GENERATOR
V
OUT
Q3
R
Q
+
Σ
S
R1
A2
+
(EXTERNAL)
NFB
+
A = 3
–
0.15Ω
R2
600kHz
OSCILLATOR
(EXTERNAL)
4
GND
1614 BD
4
LT1614
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APPLICATIONS INFORMATION
Shutdown Pin
3.3V
R1
V
IN
LT1614
LBO
The LT1614 has a Shutdown pin (SHDN) that must be
groundedtoshutthedevicedownortiedtoavoltageequal
or greater than VIN to operate. The shutdown circuit is
shown in Figure 1.
1M
LBI
+
–
TO PROCESSOR
R2
100k
200mV
V
LB
– 200mV
2µA
Note that allowing SHDN to float turns on both the start-
up current (Q2) and the shutdown current (Q3) for VIN >
2VBE.TheLT1614doesn’tknowwhattodointhissituation
and behaves erratically. SHDN voltage above VIN is al-
lowed. This merely reverse-biases Q3’s base emitter junc-
tion, a benign condition.
R1 =
INTERNAL
REFERENCE
GND
1614 F02
Figure 2. Setting Low-Battery Detector Trip Point
V
IN
200k
Q3
V
IN
R2
2N3906
REF
LBO
LBI
SHUTDOWN
400k
CURRENT
LT1614
SHDN
V
200k
200mV
+
GND
10k
10µF
START-UP
CURRENT
1614 F03
Q2
Figure 3. Accessing 200mV Reference
Q1
1614 F01
Coupled Inductors
Figure 1. Shutdown Circuit
The applications shown in this data sheet use two un-
coupled inductors because the Murata units specified are
small and inexpensive. This topology can also be used
with a coupled inductor as shown in Figure 4. Be sure to
get the phasing right.
Low-Battery Detector
The LT1614’s low-battery detector is a simple PNP input
gain stage with an open collector NPN output. The nega-
tive input of the gain stage is tied internally to a 200mV
reference. The positive input is the LBI pin. Arrangement
as a low-battery detector is straightforward. Figure 2
details hookup. R1 and R2 need only be low enough in
value so that the bias current of the LBI pin doesn’t cause
large errors. For R2, 100k is adequate. The 200mV refer-
ence can also be accessed as shown in Figure 3.
C3
1µF
L1A
10µH
L1B
10µH
V
•
•
IN
5V
V
OUT
V
SW
IN
–5V
+
SHDN
C1
33µF
200mA
69.8k
LT1614
C2
33µF
D1
V
C
NFB
+
GND
24.9k
100k
1nF
1614 F04
C1, C2: AVX TAJB336M010
C3: AVX 1206CY106
D1: MBR0520
L1: COILTRONICS CTX10-1
Figure 4. 5V to –5V Converter with Coupled Inductor
5
LT1614
TYPICAL APPLICATION
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5V to –15V/80mA DC/DC Converter
C1
1µF
L1
22µH
L2
22µH
V
IN
5V
V
OUT
V
SW
IN
–15V
+
SHDN
80mA
255k
22µF
LT1614
10µF
25V
D1
NFB
V
C
+
GND
24.9k
100k
1nF
1614 TA05
C1: 25V, Y5V
D1: MBR0520
L1, L2: MURATA LQH3C220
5V to –15V Converter Efficiency
80
75
70
65
60
55
50
1
10
100
LOAD CURRENT (mA)
1614 TA06
6
LT1614
U
PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted.
MS8 Package
8-Lead Plastic MSOP
(LTC DWG # 05-08-1660)
0.118 ± 0.004*
(3.00 ± 0.102)
8
7
6
5
0.118 ± 0.004**
(3.00 ± 0.102)
0.192 ± 0.004
(4.88 ± 0.10)
1
2
3
4
0.040 ± 0.006
(1.02 ± 0.15)
0.034 ± 0.004
(0.86 ± 0.102)
0.007
(0.18)
0° – 6° TYP
SEATING
PLANE
0.012
(0.30)
REF
0.021 ± 0.006
(0.53 ± 0.015)
0.006 ± 0.004
(0.15 ± 0.102)
MSOP (MS8) 1197
0.0256
(0.65)
TYP
*
DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH,
PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
S8 Package
8-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.189 – 0.197*
(4.801 – 5.004)
7
5
8
6
0.150 – 0.157**
(3.810 – 3.988)
0.228 – 0.244
(5.791 – 6.197)
1
0.053 – 0.069
3
4
2
0.010 – 0.020
(0.254 – 0.508)
× 45°
(1.346 – 1.752)
0.004 – 0.010
(0.101 – 0.254)
0.008 – 0.010
(0.203 – 0.254)
0°– 8° TYP
0.016 – 0.050
0.406 – 1.270
0.050
(1.270)
TYP
0.014 – 0.019
(0.355 – 0.483)
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
SO8 0996
7
LT1614
TYPICAL APPLICATION
U
3.3V to –3.1V/200mA DC/DC Converter
C1
1µF
L1
22µH
L2
22µH
V
IN
3.3V
V
OUT
V
SW
FB
IN
–3.1V
SHDN
+
200mA
18.7k
LT1614
22µF
D1
V
C
22µF
+
GND
12.7k
100k
1nF
1614 TA03
C1: AVX1206CY106
D1: MBR0520
L1, L2: MURATA LQH3C220
3.3V to –3.1V Converter Efficiency
80
70
60
50
40
30
20
3
10
30
100
300
LOAD CURRENT (mA)
1614 TA04
RELATED PARTS
PART NUMBER
LTC®1174
LT1307
DESCRIPTION
COMMENTS
High Efficiency Step-Down and Inverting DC/DC Converter
Single Cell Micropower 600kHz PWM DC/DC Converter
Single Cell High Current Micropower 600kHz Boost Converter
Micropower Boost DC/DC Converter
Selectable I
= 300mA or 600mA
PEAK
3.3V at 75mA from 1 Cell, MSOP Package
5V at 1A from a Single Li-Ion Cell, SO-8 Package
Programmable Peak Current Limit, MSOP Package
2 Cells to 3.3V at 200mA, MSOP Package
LT1308
LT1316
LT1317
Micropower 600kHz PWM DC/DC Converter
LTC1474
LT1610
Low Quiescent Current High Efficiency DC/DC Converter
1.7MHz Single Cell Micropower DC/DC Converter
I = 10µA, Programmable Peak Current Limit, MSOP
Q
5V at 200mA from 3.3V, MSOP Package
1614i LT/GP 0798 4K • PRINTED IN THE USA
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
8
●
●
(408) 432-1900 FAX: (408) 434-0507 TELEX: 499-3977
LINEAR TECHNOLOGY CORPORATION 1998
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