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PDF LTC3260 Data sheet ( Hoja de datos )
| Número de pieza | LTC3260 | |
| Descripción | Low Noise Dual Supply Inverting Charge Pump | |
| Fabricantes | Linear | |
| Logotipo |  |
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LTC3260
Low Noise Dual Supply
Inverting Charge Pump
FEATURES
n VIN Range: 4.5V to 32V
n Inverting Charge Pump Generates –VIN
n Charge Pump Output Current Up to 100mA
n Low Noise Negative LDO Post Regulator
(ILDO– = 50mA Max)
n Low Noise Independent Positive LDO Regulator
(ILDO+ = 50mA Max)
n 100µA Quiescent Current in Burst Mode® Operation
with Both LDO Regulators On
n 50kHz to 500kHz Programmable Oscillator Frequency
n Stable with Ceramic Capacitors
n Short-Circuit/Thermal Protection
n Low Profile 3mm × 4mm 14-Pin DFN and Thermally
Enhanced 16-Pin MSOP Packages
APPLICATIONS
n Low Noise Bipolar/Inverting Supplies
n Industrial/Instrumentation Low Noise Bias
Generators
n Portable Medical Equipment
n Portable Instruments
DESCRIPTION
The LTC®3260 is a low noise dual polarity output power
supply that includes an inverting charge pump with both
positive and negative LDO regulators. The charge pump
operates over a wide 4.5V to 32V input range and can deliver
up to 100mA of output current. Each LDO regulator can
provide up to 50mA of output current. The negative LDO
post regulator is powered from the charge pump output.
The LDO output voltages can be adjusted using external
resistor dividers.
The charge pump employs either low quiescent current
Burst Mode operation or low noise constant frequency
mode. In Burst Mode operation the charge pump VOUT
regulates to –0.94 • VIN, and the LTC3260 draws only
100µA of quiescent current with both LDO regulators on.
In constant frequency mode the charge pump produces
an output equal to –VIN and operates at a fixed 500kHz
or to a programmed value between 50kHz to 500kHz us-
ingwww.DataSheet.co.kr an external resistor. The LTC3260 is available in low
profile (0.75mm) 3mm x 4mm 14-pin DFN and thermally
enhanced 16-pin MSOP packages.
L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks
and ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
TYPICAL APPLICATION
±12V Outputs from a Single 15V Input
15V
–15V
10µF
1µF
VIN LDO+
LTC3260
EN+ ADJ+
EN– BYP+
MODE
C+
C–
GND
BYP–
ADJ–
VOUT
LDO–
10µF
RT
200k
12V
10µF 909k
10nF
10nF
100k
100k
10µF
3260 TA01a
909k
–12V
LDO Rejection of VOUT Ripple
VLDO+
10mV/DIV
AC-COUPLED
VLDO–
10mV/DIV
AC-COUPLED
VOUT
10mV/DIV
AC-COUPLED
VVVILLNDDOO=+–1==5V1–21V2V
IfIOLLDDSOOC+–==–5550000mmkHAAz
1µs/DIV
3260 TA01b
3260f
1
Datasheet pdf - http://www.DataSheet4U.net/
1 page  
TYPICAL PERFORMANCE CHARACTERISTICS
(TA = 25°C, CFLY = 1µF, CIN = COUT = CLDO+ = CLDO– = 10µF unless otherwise noted)
Effective Open-Loop Resistance
vs Temperature
60 fOSC = 500kHz
50
40
30
20
10
0
–50 –25
VIN = 32V
VIN = 25V
VIN = 12V
0 25 50 75 100 125 150
TEMPERATURE (°C)
3620 G07
Effective Open-Loop Resistance
vs Supply Voltage
90
80
70 fOSC = 200kHz
60
50
40 fOSC = 500kHz
30
20
10
0
0 5 10 15 20 25 30 35
SUPPLY VOLTAGE (V)
3260 G10
vVsOUSTuSpphloyrtV-Colitracgueit Current
250
200 RT = GND
150
100 RT = 200kΩ
50
0
0 5 10 15 20 25 30 35
SUPPLY VOLTAGE (V)
3260 G08
ADJ+ Pin Voltage vs Temperature
1.224
1.212
1.200
www.DataSheet.co.kr
1.188
1.176
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
3260 G11
LTC3260
vVsolOtaugtpeuLtoCsusrr(eVnINt (–C|oVnOsUtTa|n)t
Frequency Mode)
3.0 VIN = 12V
2.5 fOSC = 200kHz
2.0
fOSC = 50kHz
1.5
1.0
0.5
0
0.1 1
fOSC = 500kHz
10 100
OUTPUT CURRENT (mA)
LDO+ Dropout Voltage
vs Temperature
800
700
VILIDNO=+
12V
= 50mA
3260 G09
600
500
400
300
200
100
0
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
3260 G12
LDO+ Supply Rejection
60
50
40
30
20
10
IVVLILDNDOO=++6==.555V0VmA
0
VCRLDIPOP+LE=
= 50mVRMS
10µF
0.1 1 10
100
FREQUENCY (kHz)
1000
3260 G13
LDO+ GND Pin Current vs ILOAD
0.14
VIN = 12V
0.12
0.10
0.08
0.06
0.04
0.02
0
0 1 10 100
ILOAD (mA)
3260 G14
LDO+ Load Regulation
1.2006
1.2004
VIN = 12V
UNITY GAIN
1.2002
1.2000
1.1998
1.1996
1.1994
0.1
1 10
ILDO+ (mA)
100
3260 G15
3260f
5
Datasheet pdf - http://www.DataSheet4U.net/
5 Page 
LTC3260
APPLICATIONS INFORMATION
Effective Open-Loop Output Resistance
The effective open-loop output resistance (ROL) of a charge
pump is a very important parameter which determines the
strength of the charge pump. The value of this parameter
depends on many factors such as the oscillator frequency
(fOSC), value of the flying capacitor (CFLY), the nonoverlap
time, the internal switch resistances (RS) and the ESR of
the external capacitors.
Typical ROL values as a function of temperature are shown
in Figure 4
60 fOSC = 500kHz
50
40
30
20
10
0
–50 –25
VIN = 32V
VIN = 25V
VIN = 12V
0 25 50 75 100 125 150
TEMPERATURE (°C)
3620 F04
Figure 4. Typical ROL vs Temperature
Input/Output Capacitor Selection
The style and value of capacitors used with the LTC3260
determine several important parameters such as regulator
control loop stability, output ripple, charge pump strength
and minimum turn-on time. To reduce noise and ripple,
it is recommended that low ESR ceramic capacitors be
used for the charge pump and LDO outputs. All capacitors
should retain at least 2µF of capacitance over operating
temperature and bias voltage. Tantalum and aluminum
capacitors can be used in parallel with a ceramic capacitor
to increase the total capacitance but should not be used
alone because of their high ESR. In constant frequency
mode, the value of COUT directly controls the amount of
output ripple for a given load current. Increasing the size of
COUT will reduce the output ripple at the expense of higher
minimum turn-on time. The peak-to-peak output ripple at
the VOUT pin is approximately given by the expression:
VRIPPLE(P-P)
≈
IOUT
COUT
1
fOSC
–
tON
where COUT is the value of the output capacitor, fOSC is the
oscillator frequency and tON is the on-time of the oscillator
(1µs typical).
Just as the value of COUT controls the amount of output
ripple, the value of CIN controls the amount of ripple present
at the input (VIN) pin. The amount of bypass capacitance
required at the input depends on the source impedance
driving VIN. For best results it is recommended that VIN
be bypassed with at least 2µF of low ESR capacitance. A
high ESR capacitor such as tantalum or aluminum will
have higher input noise than a low ESR ceramic capacitor.
Therefore, a ceramic capacitor is recommended as the
main bypass capacitance with a tantalum or aluminum
capacitor used in parallel if desired.
Flying Capacitor Selectionwww.DataSheet.co.kr
The flying capacitor controls the strength of the charge
pump. A 1µF or greater ceramic capacitor is suggested
for the flying capacitor for applications requiring the full
rated output current of the charge pump.
For very light load applications, the flying capacitor may
be reduced to save space or cost. For example, a 0.2µF
capacitor might be sufficient for load currents up to 20mA.
A smaller flying capacitor leads to a larger effective open-
loop resistance (ROL) and thus limits the maximum load
current that can be delivered by the charge pump.
Ceramic Capacitors
Ceramic capacitors of different materials lose their capaci-
tance with higher temperature and voltage at different rates.
For example, a capacitor made of X5R or X7R material
will retain most of its capacitance from –40°C to 85°C
whereas a Z5U or Y5V style capacitor will lose considerable
capacitance over that range. Z5U and Y5V capacitors may
3260f
11
Datasheet pdf - http://www.DataSheet4U.net/
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LTC3260.PDF ] | |
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