LT1614

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High Voltage, Low Quiescent Current Inverting Charge Pump The L TC®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 • VIN and the L TC3261 draws only 60μA of quiescent current. In constant frequency mode the charge pump produces an output equal to –V IN and operates at a fixed 500kHz or to a programmed frequency between 50kHz to 500kHz using an external resistor. The L TC3261 is available in a thermally enhanced 12-pin MSOP package.

APPLICATIONS

n 4.5V to 32V V IN Range n Inverting Charge Pump Generates –V IN n 60μA Quiescent Current in Burst Mode ® Operation n Charge Pump Output Current Up to 100mA n 50kHz to 500kHz Programmable Oscillator Frequency n Short-Circuit/Thermal Protection n Low Profile Thermally Enhanced 12-Pin MSOP Package n Bipolar/Inverting Supplies n Industrial/Instrumentation Bias Generators n Portable Medical Equipment n Portable Instruments L, L T , L TC, L TM, 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

1μF VOUT Ripple 100μs/DIV VOUT 10mV/DIV AC-COUPLED VOUT = –14.8V VOUT = –14.1V MODE = L MODE = HVOUT 200mV/DIV AC-COUPLED

3261 TA01a

VIN = 15V fOSC = 500kHz IOUT = 5mA

V Operating Junction Temperature Range (Notes 1, 3) NC RT NC V OUT NC NC MODE EN V IN NC TOP VIEW MSE PACKAGE 12-LEAD PLASTIC MSOP GND TJMAX = 150°C, θJA = 40°C/W EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB PIN CONFIGURATION ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE L TC3261EMSE#PBF L TC3261EMSE#TRPBF 3261 12-Lead Plastic MSOP –40°C to 125°C L TC3261IMSE#PBF L TC3261IMSE#TRPBF 3261 12-Lead Plastic MSOP –40°C to 125°C Consult L TC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container . Consult L TC Marketing for information on non-standard lead based finish parts. For more information on lead free part marking, go to: http://www.linear .com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear .com/tapeandreel/

ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = EN = 12V , MODE = 0V , RT = 200kΩ. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Charge Pump V IN Input Voltage Range l 4.5 32 V VUVLO VIN Undervoltage Lockout Threshold V IN Rising VIN Falling l l 3.4 3.8 3.6 V IVIN VIN Quiescent Current Shutdown, = EN = 0V MODE = VIN, IVOUT = 0mA MODE = 0V , IVOUT = 0mA 3.5 120 5.5 μA μA mA VRT RT Regulation Voltage 1.200 V VOUT VOUT Regulation Voltage MODE = 12V MODE = 0V –0.94 • VIN –VIN V V fOSC Oscillator Frequency RT = GND 450 500 550 KHz ROUT Charge Pump Output Impedance MODE = 0V , RT = GND 32 Ω ISHORT_CKT Max IVOUT Short-Circuit Current V OUT = GND, RT = GND l 100 160 250 mA VMODE(H) MODE Threshold Rising l 1.1 2 V VMODE(L) MODE Threshold Falling l 0.4 1.0 V IMODE MODE Pin Internal Pull-Down Current V IN = MODE = 32V 0.7 μA VEN(H) EN Threshold Rising l 1.1 2 V VEN(L) EN Threshold Falling l 0.4 1.0 V IEN EN Pin Internal Pull-Down Current V IN = EN = 32V 0.7 μA Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: The L TC3261 is tested under pulsed load conditions such that T J ≈ TA. The L TC3261E is guaranteed to meet specifications from 0°C to 85°C junction temperature. Specifications over the –40°C to 125°C operating junction temperature range are assured by design, characterization and correlation with statistical process controls. The L TC3261I is guaranteed over the –40°C to 125°C operating junction temperature range. High junction temperatures degrade operating lifetimes; operating lifetime is derated for junction temperatures greater than 125°C. Note that the maximum ambient temperature consistent with these specifications is determined by specific operating conditions in conjunction with board layout, the rated package thermal impedance and other environmental factors. The junction temperature (T J, in °C) is calculated from the ambient temperature (TA, in °C) and power dissipation (PD, in Watts) according to the formula: T J = TA + (PD • θJA), where θJA = 40°C/W is the package thermal impedance. Note 3: This IC includes overtemperature protection that is intended to protect the device during momentary overload conditions. Junction temperatures will exceed 150°C when overtemperature protection is active. Continuous operation above the specified maximum operating junction temperature may result in device degradation or failure.

TYPICAL PERFORMANCE CHARACTERISTICS Oscillator Frequency vs Supply Voltage Effective Open-Loop Resistance vs Temperature Quiescent Current vs Supply Voltage (Constant Frequency Mode) Quiescent Current vs Temperature (Constant Frequency Mode) Oscillator Frequency vs RT V OUT Short-Circuit Current vs Supply Voltage VOUT Short Circuit Current vs Temperature Shutdown Current vs Temperature Quiescent Current vs Temperature (Burst Mode Operation) (TA = 25°C, CFL Y = 1μF , CIN = COUT = 10μF unless otherwise noted) SUPPL Y VOL TAGE (V) 500 600 400 300 200 100 20 25 3010 1553 5

3261 G01

RT = GND RT = 200kΩ OSCILLATOR FREQUENCY (kHz) RT (kΩ) 500 600 400 300 200 100 100 100010 10000

3261 G02

OSCILLATOR FREQUENCY (kHz) TEMPERATURE (°C) –50 5025 100 750–25 150 125

3261 G03

SHUTDOWN CURRENT (μA) VIN = 5V VIN = 12V VIN = 32V TEMPERATURE (°C) –50 140 100 120 5025 100 750–25 150 125

3261 G04

QUIESCENT CURRENT (μA) RT = GND VIN = 32V VIN = 12V VIN = 5V SUPPL Y VOL TAGE (V) 1510 25 2053 5 30

3261 G05

QUIESCENT CURRENT (mA) fOSC = 50kHz fOSC = 200kHz fOSC = 500kHz TEMPERATURE (°C) –50 50250 100 75–25 150 125

3261 G06

QUIESCENT CURRENT (mA) fOSC = 50kHz fOSC = 200kHz fOSC = 500kHz VIN = 12V TEMPERATURE (°C) –50 50250 100 75–25 150 125

3261 G07

EFFECTIVE OPEN LOOP RESISTANCE (Ω) VIN = 12V VIN = 25V VIN = 32V fOSC = 500kHz SUPPL Y VOL TAGE (V) 250 150 200 100 151052 5 20 35 30

3261 G08

VOUT SHORT CIRCUIT CURRENT (mA) fOSC = 500kHz fOSC = 200kHz TEMPERATURE (°C) –50 100 200 180 160 140 120 –25 0 25 50 125 75 100

3261 G8b

VOUT SHORT CIRCUIT CURRENT (mA) VIN = 12V RT = GND

TYPICAL PERFORMANCE CHARACTERISTICS Voltage Loss (VIN – |VOUT|) vs Output Current (Constant Frequency Mode) A = 25°C, CFL Y = 1μF , CIN = COUT = 10μF unless otherwise noted) Effective Open-Loop Resistance vs Supply Voltage Average Input Current vs Output Current VOUT Load Transient Burst Mode Operation (MODE = H) VOUT Ripple VOUT Transient (MODE = Low to High) OUTPUT CURRENT (mA) 0.1 0.0 3.0 2.0 2.5 1.0 0.5 1.5 1 100 10

3261 G09

VOL TAGE LOSS (V) fOSC = 500kHz fOSC = 200kHz fOSC = 50kHz VIN = 12V SUPPL Y VOL TAGE (V) 5 1 01 52 0 3 5 25 30

3261 G10

EFFECTIVE OPEN LOOP RESISTANCE (Ω) fOSC = 200kHz fOSC = 500kHz VOUT 500mV/DIV AC-COUPLED 2ms/DIV 3261 G11VIN = 12V fOSC = 500kHz –5mA IOUT –50mA VOUT 500mV/DIV AC-COUPLED 2ms/DIV 3261 G12VIN = 12V fOSC = 500kHz IOUT = –5mA MODE OUTPUT CURRENT (mA) 0.1 0.1 100 1 100 10

3261 G13

AVERAGE INPUT CURRENT (mA) MODE = L MODE = H VIN = 12V fOSC = 500kHz 100μs/DIV VOUT 10mV/DIV AC-COUPLED VOUT 200mV/DIV AC-COUPLED

3261 G14

VIN = 15V fOSC = 500kHz IOUT = 5mA MODE = L MODE = H

13 GND

C+ C– 9 4 EN MODE RT PIN FUNCTIONS NC (Pins 1, 3, 6, 7,12): No Connect Pins. These pins are not connected to the L TC3261 die. These pins should be left floating or connected to ground. Pins 6 and 7 can also be shorted to adjacent pins. RT (Pin 2): Input Connection for Programming the Switch- ing Frequency. The RT pin servos to a fixed 1.2V when the EN pin is driven to a logic “high”. A resistor from RT to GND sets the charge pump switching frequency. If the RT pin is tied to GND, the switching frequency defaults to a fixed 500kHz. V OUT (Pin 4): Charge Pump Output Voltage. In constant frequency mode (MODE = low) this pin is driven to –VIN. In Burst Mode operation, (MODE = high) this pin voltage is regulated to –0.94 • V IN using an internal burst comparator with hysteretic control. C– (Pin 5): Flying Capacitor Negative Connection. C+ (Pin 8): Flying Capacitor Positive Connection. VIN (Pin 9): Input Voltage for the Charge Pump. VIN should be bypassed with a low impedance ceramic capacitor . EN (Pin 10): Logic Input. A logic “high” on the EN pin enables the inverting charge pump. MODE (Pin 12): Logic Input. The MODE pin deter- mines the charge pump operating mode. A logic “high” on the MODE pin forces the charge pump into Burst Mode operation regulating V OUT to approximately –0.94 • VIN with hysteretic control. A logic “low” on the MODE pin forces the charge pump to operate as an open- loop inverter with a constant switching frequency. The switching frequency in both modes is determined by an external resistor from the RT pin to GND. In Burst Mode, this represents the frequency of the burst cycles before the part enters the low quiescent current sleep state. GND (Exposed Pad Pin 13): Ground. The exposed pack- age pad is ground and must be soldered to the PC board ground plane for proper functionality and for rated thermal performance.

supports a wide input power supply range from 4.5V to 32V . the beginning of a clock cycle, switches S1 and S2 are closed. –VIN less any voltage drop due to the load current on VOUT. the part operates at a constant frequency of 500kHz. higher output ripple and is ideal for light load operation. and optimizes the duration of the low current sleep state. Figure 1. Oscillator Frequency vs RT shutdown or thermal shutdown. mentary overload conditions outside normal operation. erating junction temperature may impair device reliability.

3261 F01

Figure 2. Typical ROL vs Temperature

• 1 fOSC –t ON where fOSC is the oscillator frequency t ON is the on-time of the oscillator (1μs) typical and COUT is the value of the output capacitor . Just as the value of C OUT 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 V IN. For best results it is recommended that V IN 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 Selection 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 (R OL) 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 also have a poor voltage coefficient causing them to lose 60% or more of their capacitance when the rated voltage is applied. Therefore when comparing different capacitors, it is often more ap- propriate to compare the amount of achievable capacitance for a given case size rather than discussing the specified capacitance value. The capacitor manufacture’s data sheet Input/Output Capacitor Selection The style and value of capacitors used with the L TC3261 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 output. The charge pump output capacitor 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 C OUT directly controls the amount of output ripple for a given load current. Increasing the size of C OUT will reduce the output ripple at the expense of higher minimum turn-on time. The peak-to-peak output ripple at the V OUT pin is approximately given by the expression: TEMPERATURE (°C) –50 50250 100 75–25 150 125

3261 F02

capacitor manufacturers and their websites. tions. Figure 3 shows an example layout for the L TC3261. close to sensitive pins such as the RT pin . of the package and PC board considerably. under the line shown for a given ambient temperature. where IOUT denotes output current at the VOUT pin. the part will be in thermal shutdown. Figure 3. Recommended Layout Figure 4. Maximum Power Dissipation vs Ambient Temperature

3261 F04

3261 F03

3261 TA06

4.5V TO 32V NOTE: I2VINt *–2VINt *OUT < = 100mA ~ 2VIN ~ –2VIN –VIN 4.7μF 50V 1μF 50V 1μF 50V 1μF 50V 4.7μF 50V 1N4148 4.7μF 100V MODE RT C VIN VOUT EN GND L TC3261 4.7μF 100V 1N4148 1N4148 1N4148

3261 TA07

4.5V TO 32V 4.7μF 50V 1μF 50V 1μF 50V MBR0540 MBR0540 MBR0540 MODE RT VIN VOUT VOUT EN GND L TC3261 4.7μF 50V VOUT – VIN –Vf –| IOUT | tROL 2 –Vf High Input Divide by 2 Voltage Divider Inverting Charge Pump with Bipolar Doubler High Voltage to Inverted Low Voltage Charge Pump 4.7μF 25V 1μF 50V 9V TO 32V VIN/2 4.7μF 50V VIN VOUT MODE RT EN GND

3261 TA04

NOTE: MINIMUM LOAD OF 120μA IS REQUIRED TO ASSURE START-UP

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 representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. PACKAGE DESCRIPTION MSOP (MSE12) 0911 REV F 0.53 ± 0.152 (.021 ± .006) SEATING PLANE 0.18 (.007) 1.10 (.043) MAX 0.22 – 0.38 (.009 – .015) TYP 0.86 (.034) REF 0.650 (.0256) BSC 12 11 10 9 8 7 DETAIL “B” 1 6 NOTE: 1. DIMENSIONS IN MILLIMETER/(INCH) 2. DRAWING NOT TO SCALE 3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX 6. EXPOSED PAD DIMENSION DOES INCLUDE MOLD FLASH. MOLD FLASH ON E-PAD SHALL NOT EXCEED 0.254mm (.010") PER SIDE. 0.254 (.010) 0° – 6° TYP DETAIL “A” DETAIL “A” GAUGE PLANE RECOMMENDED SOLDER PAD LAYOUT BOTTOM VIEW OF EXPOSED PAD OPTION 2.845 ± 0.102 (.112 ± .004) 4.039 ± 0.102 (.159 ± .004) (NOTE 3) 1.651 ± 0.102 (.065 ± .004) 1.651 ± 0.102 (.065 ± .004) 0.1016 ± 0.0508 (.004 ± .002) 12 345 6 3.00 ± 0.102 (.118 ± .004) (NOTE 4) 0.406 ± 0.076 (.016 ± .003) REF 4.90 ± 0.152 (.193 ± .006) DETAIL “B” CORNER TAIL IS PART OF THE LEADFRAME FEATURE. FOR REFERENCE ONL Y NO MEASUREMENT PURPOSE

0.12 REF

0.35 REF 5.23 (.206) MIN 3.20 – 3.45 (.126 – .136) 0.889 ± 0.127 (.035 ± .005) 0.42 ± 0.038 (.0165 ± .0015) TYP 0.65 (.0256) BSC 12-Lead Plastic MSOP, Exposed Die Pad (Reference LTC DWG # 05-08-1666 Rev F) Please refer to http://www.linear .com/designtools/packaging/ for the most recent package drawings.

Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear .com © LINEAR TECHNOLOGY CORPORATION 2012 LT 0412 • PRINTED IN USA RELATED PARTS TYPICAL APPLICATION 24V to –24V Inverter 10μF 10μF –24V

3261 TA03

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