15143 [Linear]
Step-Up/Step-Down Switched Capacitor DC/DC Converters with Low-Battery Comparator; 升压/降压型开关电容DC / DC转换器与低电池电压比较器
| 型号： | 15143 |
| 厂家： | 
Linear |
| 描述： | Step-Up/Step-Down Switched Capacitor DC/DC Converters with Low-Battery Comparator |
| 文件： | 总8页 (文件大小：211K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC1514-3.3/LTC1514-5
Step-Up/Step-Down Switched
Capacitor DC/DC Converters
with Low-Battery Comparator
U
FEATURES
DESCRIPTION
TheLTC®1514-3.3/LTC1514-5aremicropowerswitched
capacitor DC/DC converters that produce a regulated
output voltage by either stepping up or stepping down
the input voltage. Output voltage is fixed at either 3.3V
(LTC1514-3.3) or 5V (LTC1514-5) by an internal resistor
divider.
■
3.3V or 5V Output Voltages
■
2V to 10V Input Voltage Range
■
Up to 50mA Output Current
■
■
■
■
■
■
■
■
■
Only Three External Capacitors Required
Soft Start Limits Inrush Current at Turn-On
Low Operating Current: 60µA
Low Shutdown Current: 10µA
A unique architecture allows the parts to accommodate
a wide input voltage range (2V to 10V) while maintaining
±4% regulation. Additional circuitry prevents excessive
inrush current and output voltage ripple when large VIN
to VOUT differentials are present.
Shutdown Disconnects Load from VIN
Short-Circuit and Overtemperature Protected
650kHz Switching Frequency
Low-Battery Comparator Active in Shutdown
Available in SO-8 Package
An internal uncommitted comparator is kept active in
shutdown. The comparator has an open-drain output for
flexible interfacing.
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APPLICATIONS
■
Battery-Operated Equipment
The parts are short-circuit and overtemperature pro-
tected. Battery life is maximized by very low operating
currents (ICC = 60µA typ, 10µA in shutdown). Both parts
are available in an SO-8 package.
■
Smart Card Readers
■
Local Power Supplies
■
Handheld Instruments
■
, LTC and LT are registered trademarks of Linear Technology Corporation.
Battery Backup Supplies
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TYPICAL APPLICATION
LTC1514-5 Output Voltage
vs Input Voltage
5V Step-Up/Step-Down Power Supply with Low-Battery Detect
5.2
I
= 10mA
100k
OUT
1.33M
1%
LTC1514-5
SHDN
5.1
5.0
4.9
4.8
1
2
3
4
8
7
6
5
V
= 5V
OUT
OUT
V
ON OFF
LOW BAT
OUT
I
= 50mA
LBO
LBI
V
IN
+
+
V
10µF
C1
C1
IN
0.22µF
4-CELL
NiCd
+
499k
1%
–
GND
10µF
1514 TA01
2
3
4
5
6
7
8
9
10
INPUT VOLTAGE (V)
LT1514 • TA02
1
LTC1514-3.3/LTC1514-5
W W
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ABSOLUTE MAXIMUM RATINGS
PACKAGE/ORDER INFORMATION
(Note 1)
VIN to GND................................................ –0.3V to 12V
VOUT to GND ............................................. –0.3V to 12V
SHDN, LBI, LBO to GND ........................... –0.3V to 12V
ORDER PART
NUMBER
TOP VIEW
1
2
3
4
8
7
6
5
LTC1514CS8-3.3
LTC1514CS8-5
LTC1514IS8-3.3
LTC1514IS8-5
SHDN
LBO
LBI
V
V
OUT
V
OUT Short-Circuit Duration............................. Indefinite
IN
+
Operating Temperature Range
C1
C1
Commercial ............................................. 0°C to 70°C
Industrial ........................................... –40°C to 85°C
Storage Temperature Range ................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
–
GND
S8 PACKAGE
8-LEAD PLASTIC SO
S8 PART MARKING
TJMAX = 125°C, θJA = 110°C/ W
15143 1514I3
15145 1514I5
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
VIN = 2V to 10V, SHDN = 3V, C1 = 0.22µF, CIN = COUT = 10µF, unless otherwise noted (Note 2).
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
V
V
V
V
Operating Voltage
LTC1514-3.3
LTC1514-5
●
●
2.0
2.7
8
10
V
V
IN
(LTC1514-3.3)
(LTC1514-5)
2V ≤ V ≤ 8V, I
≤ 15mA
≤ 50mA
●
●
3.17
3.17
3.3
3.3
3.43
3.43
V
V
OUT
OUT
IN
OUT
OUT
3V ≤ V ≤ 8V, I
IN
2.7V ≤ V ≤ 10V, I
≤ 15mA
≤ 50mA
●
●
4.8
4.8
5
5
5.2
5.2
V
V
IN
OUT
OUT
3.3V ≤ V ≤ 10V, I
IN
Operating Current
Shutdown Current
V
IN
V
IN
≤ 5V, I
> 5V, I
= 0, SHDN = 3V
= 0, SHDN = 3V
●
●
60
75
100
120
µA
µA
IN
IN
OUT
OUT
SHDN = 0V, V ≤ 5V
SHDN = 0V, V > 5V
●
10
20
35
µA
µA
IN
IN
Output Ripple
Full Load (Note 2)
LBI Ramping Negative
LBI = 1.145V
100
650
1.145
1
mV
P-P
Switching Frequency
LBI Trip Point
●
●
500
800
kHz
V
1.110
1.180
LBI Trip Point Hysteresis
LBI Input Current
%
●
●
●
–50
50
0.4
1
nA
V
LBO V
I
= 100µA, V = 3V
0.025
OL
SINK
IN
LBO Leakage Current
SHDN Input Threshold
V
LBO
= 5V, LBI = V
–1
µA
IN
V
V
●
●
0.4
1
1
V
V
IL
1.6
IH
SHDN Input Current
SHDN = V
SHDN = 0V
●
●
–1
–1
1
1
µA
µA
IN
I
t
Short-Circuit Current
V
= 0V
●
12
4
40
mA
ms
OUT
ON
OUT
Soft Start Turn-On Time
The
●
denotes specifications which apply over the full operating
Note 2: For V ≥ 8V, C
= 22µF.
IN
OUT
temperature range.
Note 1: Absolute Maximum Ratings are those values beyond which the life of
the device may be impaired.
2
LTC1514-3.3/LTC1514-5
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TYPICAL PERFORMANCE CHARACTERISTICS
LTC1514-3.3
LTC1514-5
LTC1514-3.3 Output Voltage
Ripple vs Input Voltage
250
Efficiency vs Output Current
Efficiency vs Output Current
100
80
60
40
20
0
100
80
60
40
20
0
V
T
= 3.3V
V
I
A
= 3.3V
OUT
A
OUT
OUT
V
IN
= 6V
V
IN
= 2.7V
= 25°C
= 10mA
V
= 2V
IN
T
= 25°C
200
150
100
50
V
= 4.4V
= 2.7V
IN
V
IN
= 3.3V
V
IN
V
IN
= 8V
C
= 10µF
OUT
V
IN
= 6V
C
= 22µF
OUT
C
= 47µF
OUT
V
A
= 5V
OUT
T
= 25°C
0
0.01
0.1
1
10
100
0.01
0.1
1
10
100
0
2
6
8
4
10
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
INPUT VOLTAGE (V)
1514 G01
1514 G02
1514 G03
LTC1514-5 Output Voltage Ripple
vs Input Voltage
LTC1514-3.3 Output Voltage
vs Input Voltage
LTC1514-5 Operating Current
vs Input Voltage
3.45
3.40
3.35
3.30
3.25
3.20
250
200
150
100
50
120
100
80
V
C
T
= 3.3V
V
I
A
= 5V
V
I
= 5V
= 0mA
OUT
OUT
A
OUT
OUT
OUT
OUT
= 10µF
= 10mA
= 25°C
T
= 25°C
C
= 10µF
OUT
25°C
85°C
C
= 22µF
OUT
60
–40°C
C
= 47µF
OUT
40
0
20
0
2
4
6
8
10
0
2
4
6
8
10
0
2
4
6
8
10
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
1514 G05
1514 G04
1514 G06
LTC1514-3.3
Efficiency vs Input Voltage
LTC1514-5
Efficiency vs Input Voltage
LTC1514-X Shutdown Supply
Current vs Input Voltage
25
20
15
10
5
100
80
60
40
20
100
80
SHDN = 0V
V
= 3.3V
V
= 5V
OUT
OUT
OUT
OUT
I
= 10mA
I
= 10mA
T
A
= 25°C
T
A
= 25°C
85°C
25°C
60
–40°C
40
0
20
0
2
4
6
8
10
0
2
4
6
8
10
2
4
6
8
10
12
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
1514 G09
1514 G07
1514 G08
3
LTC1514-3.3/LTC1514-5
U W
TYPICAL PERFORMANCE CHARACTERISTICS
LTC1514-5 Step-Down Mode
Load Transient Response
LTC1514-5 Step-Up Mode
Load Transient Response
VOUT
VOUT
AC COUPLED
100mV/DIV
AC COUPLED
100mV/DIV
50mA
0mA
IOUT
50mA/DIV
IOUT
50mA/DIV
VIN = 8V, VOUT = 5V, COUT = 10µF, TA = 25°C
VIN = 3.3V, VOUT = 5V, COUT = 10µF, TA = 25°C
1514 G10
1514 G11
W
BLOCK DIAGRAM
–
+
C1
C1
V
IN
STEP-UP/STEP-DOWN
CHARGE PUMP
V
OUT
SHDN
–
+
650kHz
OSCILLATOR
LBO
LBI
–
+
1.145V
V
REF
1514 BD
GND
U
U
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PIN FUNCTIONS
LBO (Pin 2): Open-Drain, Low-Battery Comparator Out-
put. This pin will pull low whenever the voltage on the LBI
pinislessthantheinternalreferencevoltage(1.145Vtyp).
SHDN (Pin 1): Shutdown Input. A logic low on the SHDN
pin puts the part into shutdown mode. A logic high
(VSHDN ≥ 1.6V) enables the charge pump regulator. At
high VIN voltages, the SHDN pin may still be controlled
with3VlogicwithoutcausingalargeriseinVIN quiescent
current. The SHDN pin may not float; connect to VIN if
unused.
LBI (Pin 3): Low-Battery Comparator Input. The voltage
on this pin is compared to the internal reference voltage
(1.145V). The LBO output will sink current when the
voltage on the LBI pin is less than 1.145V typ. The low-
4
LTC1514-3.3/LTC1514-5
U
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PIN FUNCTIONS
battery comparator and 1.145V reference are kept alive in
shutdown.
VIN (Pin 7): Charge Pump Input Voltage. May be between
2V and 8V (LTC1514-3.3) or between 2.7V and 10V
(LTC1514-5). VIN should be bypassed with a ≥10µF low
ESR capacitor as close as possible to the pin for best
performance.
GND (Pin 4): Ground. Should be tied to a ground plane for
best performance.
C1– (Pin 5): Charge Pump Flying Capacitor, Negative
Terminal.
C1+ (Pin 6): Charge Pump Flying Capacitor, Positive
Terminal.
VOUT (Pin 8): Regulated Output Voltage. The output volt-
age is internally set to either 3.3V (LTC1514-3.3) or to 5V
(LTC1514-5)usinganinternalresistordivider.VOUT should
be bypassed with a ≥10µF low ESR capacitor as close as
possible to the pin for best performance.
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APPLICATIONS INFORMATION
Regulator Operation
tantalum and should be 10µF or greater. If the input
source impedance is very low (<0.5Ω), CIN may not be
needed.IncreasingthesizeofCOUT to22µForgreaterwill
reduce output voltage ripple—particularly with high VIN
voltages (8V or greater). A ceramic capacitor is recom-
mended for the flying capacitor C1 with a value of 0.1µF
or 0.22µF. Smaller value flying capacitors may be used in
low output current applications.
The regulator section of the LTC1514-3.3/LTC1514-5
consists of a charge pump, reference, comparator and
some logic. The divided down output voltage is com-
pared to the internal reference voltage. When the divided
output drops below the reference voltage, the charge
pump is enabled, which boosts the output back into
regulation. Hysteresis in the comparator forces the regu-
lator to burst on and off and causes approximately
100mV of peak-to-peak ripple to appear at the output. By
enabling the charge pump only when needed, the
LTC1514-3.3 and LTC1514-5 are able to achieve high
efficiencies with low output load currents.
Output Ripple
Normal LTC1514-3.3/LTC1514-5 operation produces
voltage ripple on the VOUT pin. Output voltage ripple is
required for the parts to regulate. Low frequency ripple
exists due to the hysteresis in the sense comparator and
propagation delays in the charge pump enable/disable
circuits. High frequency ripple is also present mainly
from the ESR (equivalent series resistance) in the output
capacitor. Typical output ripple (VIN < 8V) under maxi-
mumloadis100mVpeak-to-peakwithalowESR(<0.5Ω)
10µF output capacitor. For applications requiring VIN to
exceed 8V, a 22µF or larger COUT capacitor is recom-
mended to maintain max ripple in the 100mV range.
Each part’s charge pump has a unique architecture that
allows the input voltage to be either stepped up or
stepped down to produce a regulated output. Internal
circuitry senses the VIN to VOUT differential voltage and
controls the charge pump operating mode. In addition,
the effective output impedance of the charge pump is
internally adjusted to prevent large inrush currents and
allow for a wide input voltage range. When the input
voltageislowerthantheoutputvoltage, thechargepump
operates as a step-up voltage doubler. When the input
voltage is greater than the output, the charge pump
operates as a step-down gated switch.
The magnitude of the ripple voltage depends on several
factors. High input voltages increase the output ripple
since more charge is delivered to COUT per charging
cycle. A large C1 flying capacitor (>0.22µF) also
increases ripple in step-up mode for the same reason.
Largeoutputcurrentloadand/orasmalloutputcapacitor
(<10µF) results in higher ripple due to higher output
voltage dV/dt. High ESR capacitors (ESR > 0.5Ω) on the
Capacitor Selection
For best performance, low ESR capacitors are recom-
mendedforbothCIN andCOUT toreducenoiseandripple.
The CIN and COUT capacitors should be either ceramic or
5
LTC1514-3.3/LTC1514-5
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APPLICATIONS INFORMATION
output pin cause high frequency voltage spikes on VOUT
with every clock cycle.
InternalsoftstartcircuitrycontrolstherateatwhichVOUT
may be charged from 0V to its final regulated value. The
typical start-up time from VOUT = 0V to 5V is 4ms. This
correspondstoaneffectiveVOUT chargingcurrentofonly
12.5mA for a 10µF output capacitor (27.5mA for 22µF,
etc). Note that any output current load present during
start-up will add directly to the charging currents men-
tioned above. The soft start circuitry limits start-up
current both at initial power-up and when coming out of
shutdown.
There are several ways to reduce the output voltage
ripple. A larger COUT capacitor (22µF or greater) will
reduce both the low and high frequency ripple due to the
lowerCOUT charginganddischargingdV/dtandthelower
ESR typically found with higher value (larger case size)
capacitors. A low ESR ceramic output capacitor will
minimize the high frequency ripple, but will not reduce
the low frequency ripple unless a high capacitance value
is chosen. A reasonable compromise is to use a 10µF to
22µF tantalum capacitor in parallel with a 1µF to 3.3µF
ceramic capacitor on VOUT to reduce both the low and
highfrequencyripple. AnRCorLCfiltermayalsobeused
to reduce high frequency voltage spikes (see Figure 1).
As the VIN (or boosted VIN) to VOUT voltage differential
grows, the effective output impedance of the charge
pump is automatically increased by internal voltage
sensing circuitry. This feature minimizes the current
spikes pulled from VIN whenever the charge pump is
enabled and helps toreduce bothinput and outputripple.
8
V
V
OUT
OUT
Protection Features
+
1µF
CERAMIC
15µF
TANTALUM
LTC1514-X
The LTC1514-X contain thermal shutdown and short-
circuitprotectionfeatures.Thepartswillshutdownwhen
the junction temperature reaches approximately 150°C
and will resume operation once the junction temperature
has dropped back to approximately 140°C. The parts will
limit output current to 12mA (typ) when a short-circuit
condition (VOUT < 100mV) exists. The parts can survive
an indefinite short to GND. The LTC1514-X devices use
a low thermal resistance SO-8 package (110°C/W vs
150°C/W for standard SO-8). This permits full output
current, even at high input supply voltages.
2Ω
8
V
V
OUT
OUT
+
+
10µF
10µF
LTC1514-X
TANTALUM
TANTALUM
1514 F01
Figure 1. Output Ripple Reduction Techniques
Inrush Currents
Low-Battery Comparator
A common problem with switched capacitor regulators
is inrush current—particularly during power-up and
coming out of shutdown mode. Whenever large VIN (or
boosted VIN) to VOUT voltage differentials are present,
most charge pumps will pull large current spikes from
the input supply. Only the effective charge pump output
impedance limits the current while the charge pump is
enabled. This may disrupt input supply regulation, espe-
cially if the input supply is a low power DC/DC converter
or linear regulator. The LTC1514-3.3/LTC1514-5 mini-
mize inrush currents both at start-up and under normal
high VIN to VOUT operation.
The internal low-battery comparator trips at 1.145 ±3%
(LBIrampingnegative). Programmingthecomparatorto
tripatahighervoltagecaneasilybedonewithanexternal
LTC1514-X
V
BAT
1
2
3
4
8
7
6
5
SHDN
LBO
LBI
V
OUT
V
R1
IN
V
= 1.145V(1 + R1/R2)
TRIP
+
(LBI RAMPING NEGATIVE)
C1
–
R2
GND
C1
1514 F02
Figure 2. Programming the Low-Battery Comparator Trip Voltage
6
LTC1514-3.3/LTC1514-5
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APPLICATIONS INFORMATION
resistor divider (see Figure 2). Since the low-battery
comparator is kept alive in shutdown, it may be used to
protect batteries against deep discharge by shutting
down the power supply when the battery voltage gets too
low. The open-drain comparator output allows for flex-
ible interfacing between the LBO output and external
logic. LBO pull-up resistors in the 50k to 1M range are
recommended.
U
TYPICAL APPLICATIONS N
3.3V Step-Up/Step-Down Supply with Power Good Output
806k
1%
100k
1
LTC1514-3.3
V
I
= 3.3V ±4%
OUT
OUT
OUT
8
7
6
5
= 15mA, V > 2V
IN
SHDN
LBO
LBI
V
OUT
ON OFF
I
= 50mA, V > 3V
IN
2
3
4
V
IN
POWER GOOD
V
IN
+
2V TO 8V
+
3V V
TRIP
10µF
C1
C1
+
0.22µF
499k
1%
–
10µF
GND
1514 TA05
Low Power Battery Backup Supply with Autoswitchover and No Reverse Current
BACKED-UP
CIRCUITRY
MAIN
5V SUPPLY
BAT54
499k
5V BACKUP SUPPLY
LTC1514-5
TP0610T
I
= 15mA
OUT
1
2
3
4
8
7
6
5
SHDN
LBO
LBI
V
OUT
1.5M
1%
TRICKLE CHARGE
V
IN
+
AND LTC1514 I
+
DD
4.6V V
499k
TRIP
10µF
C1
C1
3-CELL
0.1µF
+
499k
1%
–
NiCd BATTERY
GND
10µF
1514 TA03
Battery/External Power Autoswitch Regulator
MBR0520L
6V
WALL
ADAPTER
INPUT
499k
EXTERNAL
POWER GOOD
1M
1%
LTC1514-5
5V
1
2
3
4
8
7
6
5
+
ON OFF
SHDN
LBO
LBI
V
OUT
22µF
V
IN
+
C1
C1
3-CELL
NiCd
BATTERY
0.22µF CHARGE PATH
–
499k
1%
GND
+
10µF
1514 TA06
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.
7
LTC1514-3.3/LTC1514-5
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TYPICAL APPLICATIONS N
Low Power Dual Output Supply (Maximum Combined IOUT = 50mA)
ON OFF
10Ω
Q2
220k
1
2
3
4
8
7
6
5
Q1
V
OUT
5V ±4%
V
SHDN
LBO
V
OUT
OUT
47k
3.3V
V
IN
±4%
V
IN
750k
1%
2.2nF
2.7V TO 10V
LTC1514-5
+
+
C1
LBI
+
+
10µF
402k
1%
0.22µF
22µF
10µF
–
C1
GND
1514 TA04
Q1: TP0610T
Q2: MMBT3906LT1
Step-Up/Step-Down Power Supply with Input Autoswitching
CENTRAL SEMI
CMPD6263C
Si6943DQ
Si6943DQ
Si6943DQ
+6VDC
WALL
ADAPTER
4 × AAA
ALKALINE
CELLS
MMBZ
5235BLT1
(6.8V)
470k
EXT_PWR_GOOD
MMBD
914LT1
10k
7
10k
+
10µF
V
IN
V
25V
OUT
1
3
2
8
6
5
V
SHDN
5V
OUT
+
2.4k
50mA
+
LBI
LTC1514-5 C1
22µF
10V
0.22µF
–
1k
C1
1M
LBO
2N7002
GND
4
MMBT
3904LT1
100k
1514 TA07
MMBT
3904LT1
ON OFF
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PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted.
S8 Package
8-Lead Plastic Small Outline (Narrow 0.150)
0.189 – 0.197*
(4.801 – 5.004)
(LTC DWG # 05-08-1610)
0.010 – 0.020
(0.254 – 0.508)
7
5
8
6
× 45°
0.053 – 0.069
(1.346 – 1.752)
0.004 – 0.010
(0.101 – 0.254)
0.008 – 0.010
(0.203 – 0.254)
0°– 8° TYP
0.150 – 0.157**
(3.810 – 3.988)
0.228 – 0.244
(5.791 – 6.197)
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
SO8 0996
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
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2
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RELATED PARTS
PART NUMBER
LTC1515 Series
LTC1516
DESCRIPTION
COMMENTS
Step-Up/Step-Down Switched Capacitor DC/DC Converters with Reset V 2V to 10V, 3.3V, 5V and ADJ Versions, I
to 50mA
OUT
= 50mA (V ≥ 3V)
IN
Micropower, Regulated 5V Charge Pump DC/DC Converter
Micropower, Regulated 5V Charge Pump DC/DC Converter
Micropower, Regulated 5V Charge Pump DC/DC Converter
I
= 20mA (V ≥ 2V), I
OUT
IN
OUT IN
LTC1517-5
LTC1522
LTC1522 Without Shutdown and Packaged in SOT-23
Available in 8-Pin MSOP, 6µA Quiescent Current, I
= 20mA
OUT
LTC1555/LTC1556 SIM Power Supply and Level Translators
Step-Up/Step-Down SIM Power Supply and Level Translators
5V to –5V Conversion with Low Voltage Loss
LTC660
100mA CMOS Voltage Converter
151435f LT/TP 0298 4K • PRINTED IN USA
Linear Technology Corporation
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1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900
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FAX: (408) 434-0507 TELEX: 499-3977 www.linear-tech.com
LINEAR TECHNOLOGY CORPORATION 1997
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