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PDF LTC1751-5 Data sheet ( Hoja de datos )
| Número de pieza | LTC1751-5 | |
| Descripción | Micropower/ Regulated Charge Pump DC/DC Converters | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LTC1751/LTC1751-3.3/LTC1751-5
Micropower, Regulated
Charge Pump
DC/DC Converters
FEATURES
s 5V Output Current: 100mA (VIN ≥ 3V)
s 3.3V Output Current: 80mA (VIN ≥ 2.5V)
s Ultralow Power: 20µA Quiescent Current
s Regulated Output Voltage: 3.3V ±4%, 5V ±4%, ADJ
s No Inductors
s Short-Circuit/Thermal Protection
s VIN Range: 2V to 5.5V
s 800kHz Switching Frequency
s Very Low Shutdown Current: <2µA
s Shutdown Disconnects Load from VIN
s PowerGood/Undervoltage Output
s Adjustable Soft-Start Time
s Available in an 8-Pin MSOP Package
U
APPLICATIO S
s Li-Ion Battery Backup Supplies
s Local 3V and 5V Conversion
s Smart Card Readers
s PCMCIA Local 5V Supplies
s White LED Backlighting
DESCRIPTIO
The LTC®1751 family are micropower charge pump DC/
DC converters that produce a regulated output voltage at
up to 100mA. The input voltage range is 2V to 5.5V.
Extremely low operating current (20µA typical with no
load) and low external parts count (one flying capacitor
and two small bypass capacitors at VIN and VOUT) make
them ideally suited for small, battery-powered applica-
tions.
The LTC1751 family operate as Burst ModeTM switched
capacitor voltage doublers to achieve ultralow quiescent
current. They have thermal shutdown capability and can
survive a continuous short circuit from VOUT to GND. The
PGOOD pin on the LTC1751-3.3 and LTC1751-5 indicates
when the output voltage has reached its final value and if
the output has an undervoltage fault condition. The FB pin
of the adjustable LTC1751 can be used to program the
desired output voltage or current. An optional soft-start
capacitor may be used at the SS pin to prevent excessive
inrush current during start-up.
The LTC1751 family is available in an 8-pin MSOP
package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
TYPICAL APPLICATIO
Regulated 5V Output from a 2.7V to 5.5V Input
VIN
2.7V
TO 5.5V C2
10µF
OFF ON
3
VIN
2
VOUT
71
SHDN PGOOD
8
LTC1751-5
SS C+
6
4
GND
C– 5
R1
100k
PGOOD
CFLY
1µF
1751 TA01
CFLY = MURATA GRM39X5R105K6.3AJ
C1, C2 = MURATA GRM40X5R106K6.3AJ
VOUT
C1
10µF
5V ±4%
IOUT ≤ 100mA, VIN ≥ 3V
IOUT ≤ 50mA, VIN ≥ 2.7V
Output Voltage vs Input Voltage
5.2
IOUT = 50mA
CFLY = 1µF
COUT = 10µF
5.1
TA = 85°C
5.0 TA = 25°C
TA = –40°C
4.9
4.8
2.5
3.0 3.5 4.0 4.5
INPUT VOLTAGE (V)
5.0 5.5
1751 TA02
1
1 page  
LTC1751/LTC1751-3.3/LTC1751-5
TYPICAL PERFOR A CE CHARACTERISTICS
(LTC1751-5)
Power Efficiency vs Load Current
100
TA = 25°C
90 CFLY = 1µF
80 COUT = 10µF
VIN = 2.7V
70
VIN = 4.1V
60
Short-Circuit Output Current
vs Input Voltage
250
TA = 25°C
CFLY = 1µF
200
50 VIN = 5.5V
150
40
30
100
20
10
0
0.001
0.01 0.1 1 10 100
LOAD CURRENT (mA)
1751 G11
50
2.0 2.5
3.0 3.5 4.0 4.5
INPUT VOLTAGE (V)
5.0 5.5
1751 G12
Start-Up
Output Ripple
Load Transient Response
SHDN
2V/DIV
PGOOD
5V/DIV
VOUT
2V/DIV
VOUT
AC COUPLED
50mV/DIV
IOUT
50mA/DIV
VOUT
AC COUPLED
50mV/DIV
CSS = 10nF
2ms/DIV
1751 G13
VIN = 3V
IOUT = 100mA
COUT = 10µF
5µs/DIV
1751 G14
VIN = 3V
50µs/DIV
1751 G15
PI FU CTIO S
PGOOD (Pin 1) (LTC1751-3.3/LTC1751-5): Output Volt-
age Status Indicator. On start-up, this open-drain pin re-
mains low until the output voltage, VOUT, is within 4.5%
(typ) of its final value. Once VOUT is valid, PGOOD becomes
high-Z. If, due to a fault condition, VOUT falls 7% (typ) below
its correct regulation level, PGOOD pulls low. PGOOD may
be pulled up through an external resistor to any appropri-
ate reference level.
FB (Pin 1) (LTC1751): The voltage on this pin is compared
to the internal reference voltage (1.205V) by the error
comparator to keep the output in regulation. An external
resistor divider is required between VOUT and FB to pro-
gram the output voltage.
VOUT (Pin 2): Regulated Output Voltage. For best perfor-
mance, VOUT should be bypassed with a 6.8µF (min) low
ESR capacitor as close to the pin as possible .
VIN (Pin 3): Input Supply Voltage. VIN should be bypassed
with a 6.8µF (min) low ESR capacitor.
GND (Pin 4): Ground. Should be tied to a ground plane for
best performance.
C – (Pin 5): Flying Capacitor Negative Terminal.
C+ (PIN 6): Flying Capacitor Positive Terminal.
SHDN (Pin 7): Active Low Shutdown Input. A low on
SHDN disables the device. SHDN must not be allowed to
float.
SS (Pin 8): Soft-Start Programming Pin. A capacitor on SS
programs the start-up time of the charge pump so that
large start-up input current is eliminated.
5
5 Page 
LTC1751/LTC1751-3.3/LTC1751-5
TYPICAL APPLICATIO S
USB Port to Regulated 5V Power Supply with Soft-Start
1µF
1Ω
10µF
5
C–
3
VIN
6
C+
VOUT
2
7 LTC1751-5
SHDN
8
SS
1nF
1
PGOOD
GND
4
10µF
VOUT = 5V
100k
PGOOD
1751 TA04
2-Cell NiCd or NiMH to 3.3V with Low Standby Current
1µF
2-CELL
NiCd OR
NiMH
+
+
OFF ON
56
C–
3
VIN
C+
2
VOUT
10µF LTC1751-3.3
7
SHDN
8 SS
1
PGOOD
1nF GND
4
10µF
3.3V
40mA
100k
PGOOD
1751 TA06
Boosted Constant Current Source
1µF
VIN
10µF
OFF ON
5
C–
3
VIN
6
C+
VOUT
2
LTC1751
7
SHDN
8 SS
1
FB
GND
4
10µF
IL
=
1.205V
RX
VOUT ≤ 2 VIN
LOAD
RX
1751 TA07
VIN = 5V
10µF
Low Power Battery Backup with Auto Switchover and No Reverse Current
Si4435DY
1µF
75k
IN4148
1.43M
3-CELL
NiCd
BATTERY
+
+
10µF
+
330pF
5
C–
3
VIN
6
C+
VOUT
2
LTC1751-5
8
SS
1
PGOOD
7
SHDN
GND
4
BAT54C
10µF
VOUT = 5V
IOUT ≤ 100mA
100k
HIGH = BACKUP MODE
475k
7
4 LTC1540
–8
3+
6
10k 5 HYST
21
1M
1751 TA05
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-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
11
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet LTC1751-5.PDF ] | |
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