Datasheet

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LTC3261

3261fb

For more information www.linear.com/3261

Typical applicaTion

FeaTures DescripTion

High Voltage,

Low Quiescent Current

Inverting Charge Pump

The LT C

3261 is a high voltage inverting charge pump

that operates over a wide 4.5V to 32V input range and

is capable of delivering up to 100mA of output current.

The charge pump employs either low quiescent current

Burst Mode operation or low noise constant frequency

mode. In Burst Mode operation the charge pump V

OUT

regulates to –0.94 • V

and the LTC3261 draws only 60µA

of quiescent current. In constant frequency mode the charge

pump produces an output equal to –V

and operates at

a fixed 500kHz or to a programmed frequency between

50kHz to 500kHz using an external resistor. The LTC3261

is available in a thermally enhanced 12-pin MSOP package.

applicaTions

4.5V to 32V V

Range

Inverting Charge Pump Generates –V

60µA Quiescent Current in Burst Mode

Operation

Charge Pump Output Current Up to 100mA

50kHz to 500kHz Programmable Oscillator

Frequency

Short-Circuit/Thermal Protection

Low Profile Thermally Enhanced 12-Pin MSOP

Package

Bipolar/Inverting Supplies

Industrial/Instrumentation Bias Generators

Portable Medical Equipment

Portable Instruments

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.

15V to –15V Inverter

10µF10µF

–15V

3261 TA01

OUT

15V

LTC3261

GND

MODE

–

1µF

OUT

Ripple

100µs/DIV

OUT

10mV/DIV

AC-COUPLED

OUT

= –14.8V

OUT

= –14.1V

MODE = L

MODE = H

OUT

200mV/DIV

AC-COUPLED

3261 TA01a

= 15V

OSC

= 500kHz

OUT

= 5mA

Summary of content (14 pages)

PAGE 1
LTC3261 High Voltage, Low Quiescent Current Inverting Charge Pump Description Features n n n n n n n 4.
PAGE 2
LTC3261 Absolute Maximum Ratings Pin Configuration (Notes 1, 3) VIN, EN, MODE............................................ –0.3V to 36V VOUT............................................................ –36V to 0.3V RT................................................................. –0.3V to 6V VOUT Short-Circuit Duration.............................. Indefinite Operating Junction Temperature Range (Note 2)................................................... –55°C to 150°C Storage Temperature Range..........
PAGE 3
LTC3261 Electrical Characteristics The l denotes the specifications which apply over the specified operating junction temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = EN = 12V, MODE = 0V, RT = 200kΩ.
PAGE 4
LTC3261 Typical Performance Characteristics (TA = 25°C, CFLY = 1µF, CIN = COUT = 10µF unless otherwise noted) 600 400 300 RT = 200kΩ 200 100 0 5 10 15 20 25 SUPPLY VOLTAGE (V) 30 500 400 300 200 100 0 35 1 10 100 RT (kΩ) 1000 3261 G01 14 80 VIN = 12V 60 VIN = 5V 40 20 0 6 4 40 35 30 25 20 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 3261 G07 fOSC = 500kHz fOSC = 200kHz fOSC = 50kHz 6 5 4 3 2 1 0 5 10 15 20 25 SUPPLY VOLTAGE (V) 30 0 –50 –25 35 0 25 50 75 100 125 150 TEMP
PAGE 5
LTC3261 Typical Performance Characteristics (TA = 25°C, CFLY = 1µF, CIN = COUT = 10µF unless otherwise noted) Voltage Loss (VIN – |VOUT|) vs Output Current (Constant Frequency Mode) fOSC = 50kHz fOSC = 200kHz fOSC = 500kHz VOLTAGE LOSS (V) 2.5 VIN = 12V 2.0 1.5 1.0 0.5 0.0 0.
PAGE 6
LTC3261 Pin Functions NC (Pins 1, 3, 6, 7,12): No Connect Pins. These pins are not connected to the LTC3261 die. These pins should be left floating or connected to ground. Pins 6 and 7 can also be shorted to adjacent pins. VIN (Pin 9): Input Voltage for the Charge Pump. VIN should be bypassed with a low impedance ceramic capacitor. RT (Pin 2): Input Connection for Programming the Switching Frequency. The RT pin servos to a fixed 1.2V when the EN pin is driven to a logic “high”.
PAGE 7
LTC3261 Operation (Refer to the Block Diagram) Shutdown Mode In shutdown mode, all circuitry except the internal bias is turned off. The LTC3261 is in shutdown when a logic low is applied to the enable input (EN). The LTC3261 only draws 2µA (typical) from the VIN supply in shutdown. Constant Frequency Operation The LTC3261 provides low noise constant frequency operation when a logic low is applied to the MODE pin. The charge pump and oscillator circuit are enabled using the EN pin.
PAGE 8
LTC3261 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.
PAGE 9
LTC3261 Applications Information should be consulted to ensure the desired capacitance at all temperatures and voltages. Table 1 is a list of ceramic capacitor manufacturers and their websites. Table 1 AVX www.avxcorp.com Kemet www.kemet.com Murata www.murata.com Taiyo Yuden www.t-yuden.com Vishay www.vishay.com TDK www.component.tdk.
PAGE 10
LTC3261 Typical Applications High Input Divide by 2 Voltage Divider C2 1µF 50V 9V TO 32V C1 4.7µF 50V VIN C+ EN C– VOUT LTC3261 MODE RT GND 3261 TA04 VIN/2 C3 4.7µF 25V NOTE: MINIMUM LOAD OF 120µA IS REQUIRED TO ASSURE START-UP Inverting Charge Pump with Bipolar Doubler D1 1N4148 4.5V TO 32V C1 4.7µF 50V C+ VIN EN LTC3261 C– D4 1N4148 D3 1N4148 GND VOUT 3261 TA06 ~ 2VIN C5 4.7µF 100V C2 1µF 50V C3 1µF 50V C4 1µF 50V MODE RT D2 1N4148 ~ –2VIN C6 4.7µF 100V –VIN C7 4.
PAGE 11
LTC3261 Typical Applications High Voltage to Inverted Low Voltage Charge Pump 4.5V TO 32V C1 4.7µF 50V D1 MBR0540 VIN VOUT VOUT C4 4.7µF 50V EN C+ C2 1µF 50V  V –V – |I | •R  VOUT  –  IN f OUT OL –Vf  2    LTC3261 D2 MBR0540 C3 1µF 50V D3 MBR0540 C– MODE GND RT 3261 TA07 3261fb For more information www.linear.
PAGE 12
LTC3261 Package Description Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. MSE Package 12-Lead Plastic MSOP, Exposed Die Pad (Reference LTC DWG # 05-08-1666 Rev F) BOTTOM VIEW OF EXPOSED PAD OPTION 2.845 ± 0.102 (.112 ± .004) 5.23 (.206) MIN 2.845 ± 0.102 (.112 ± .004) 0.889 ± 0.127 (.035 ± .005) 6 1 1.651 ± 0.102 (.065 ± .004) 1.651 ± 0.102 3.20 – 3.45 (.065 ± .004) (.126 – .136) 12 0.65 0.42 ± 0.038 (.0256) (.0165 ± .
PAGE 13
LTC3261 Revision History REV DATE DESCRIPTION A 9/12 Changed the Operating Junction Temperature to –55°C to 150°C in the Absolute Maximum section 2 Added LTC3261HMSE and LTC3261MPMSE to Order Information table 2 Added the word junction to the heading for Electric Characteristics 3 Added LTC3261H and LTC3261MP guarantees into Note 2 following LTC3261I sentence 3 Deleted Thermal Shutdown curve from Figure 4 9 Changed two paragraphs with respect to operation at 150°C and thermal shutdown 9 Upd
PAGE 14
LTC3261 Typical Application 24V to –24V Inverter C2 1µF 8 5 + C– C 9 24V VOUT VIN C1 10µF 4 LTC3261 10 11 –24V C3 10µF EN MODE RT 2 GND 13 3261 TA03 Related Parts PART NUMBER DESCRIPTION COMMENTS LT1054/LT1054L Switched-Capacitor Voltage Converters with Regulator VIN: 3.