FEATURES APPLICATIO S TYPICAL APPLICATIO. LTC /LTC Micropower, Regulated 3.3V/5V Charge Pump with Shutdown in SOT-23 DESCRIPTIO

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1 LTC74-./LTC74- Micropower, Regulated.V/V Charge Pump with Shutdown in SOT- FEATRES ltralow Power: I IN = µa Regulated Output Voltage:.V ±4%, V ±4% V Output Current: ma (.V).V Output Current: 4mA (.V) No Inductors Needed Very Low Shutdown Current: <µa Shutdown Disconnects Load from Internal Oscillator: 6kHz Short-Circuit and Overtemperature Protected ltrasmall Application Circuit: (. Inch ) 6-Pin SOT- Package APPLICATIO S SIM Interface Supplies for GSM Cellular Telephones White LED Power Supplies Li-Ion Battery Backup Supplies Handheld Computers Smart Card Readers PCMCIA Local V Supplies DESCRIPTIO The LTC 74 is a micropower charge pump DC/DC converter that produces a regulated output. The input voltage range is V to 4.4V for.v output and.7v to.v for V output. Extremely low operating current and a low external parts count (one flying capacitor and two small bypass capacitors at and ) make the LTC74 ideally suited for small, battery-powered applications. The total component area of the application circuit shown below is only. inch. The LTC74 operates as a Burst Mode TM switched capacitor voltage doubler to produce a regulated output. It has thermal shutdown capability and can survive a continuous short circuit from to. The LTC74 is available in a 6-pin SOT- package., LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode is a trademark of Linear Technology Corporation. TYPICAL APPLICATIO µf ON/OFF 6 C + LTC74-X Regulated.V Output from V to 4.4V Input Regulated V Output from.7v to.v Input C 4 µf =.V ±4% I OT = ma TO ma, >.V I OT = ma TO 4mA, >.V = V ±4% I OT = ma TO ma, >.7V I OT = ma TO ma, >.V µf 74 TA OTPT VOLTAGE (V).4 IOT = ma C OT = µf C FLY = µf..... LTC74-. Output Voltage vs Supply Voltage T A = 8 C T A = C T A = 4 C TA OTPT VOLTAGE (V) LTC74- Output Voltage vs Supply Voltage I OT = ma C OT = µf C FLY = µf T A = C T A = 8 C T A = 4 C TA

2 LTC74-./LTC74- ABSOLTE AXI RATI GS W W W (Note ) to....v to 6V to....v to 6V to....v to 6V I OT (Note 4)... 7mA Short-Circuit Duration... Indefinite Operating Temperature Range (Note )... 4 C to 8 C Storage Temperature Range... 6 C to C Lead Temperature (Soldering, sec)... C W PACKAGE/ORDER I FOR ATIO TOP VIEW 6 C + 4 C S6 PACKAGE 6-LEAD PLASTIC SOT- T JMAX = C, θ JA = C/ W Consult factory for Industrial and Military grade parts. ORDER PART NMBER LTC74ES6-. LTC74ES6- S6 PART MARKING LTGK LTLW ELECTRICAL CHARACTERISTICS The denotes specifications which apply over the full operating temperature range, otherwise specifications are at T A = C. C FLY = µf (Note ), C IN = µf, C OT = µf. SYMBOL PARAMETER CONDITIONS MIN TYP MAX NITS LTC74-. Input Supply Voltage. 4.4 V Output Voltage.V 4.4V, I OT ma.7..4 V.V 4.4V, I OT 4mA.7..4 V I CC Operating Supply Current.V 4.4V, I OT = ma, = µa V R Output Ripple =.V, I OT = 4mA mv P-P η Efficiency =.V, I OT = ma 8 % f OSC Switching Frequency Oscillator Free Running 6 khz t ON Turn-On Time =.V, I OT = ma.8 ms I SC Output Short-Circuit Current =.V, = V, =.V 8 ma LTC74- Input Supply Voltage.7. V Output Voltage.7V.V, I OT ma V.V.V, I OT ma V I CC Operating Supply Current.7V.V, I OT = ma, = µa V R Output Ripple = V, I OT = ma 6 mv P-P η Efficiency = V, I OT = ma 8.7 % f OSC Switching Frequency Oscillator Free Running 7 khz t ON Turn-On Time = V, I OT = ma.4 ms I SC Output Short-Circuit Current = V, = V, = V ma LTC74-./LTC74- I Shutdown Supply Current.6V, I OT = ma, V = V. µa.6v <, I OT = ma, V = V. µa V IH Input Threshold (High).4 V V IL Input Threshold (Low). V I IH Input Current (High) = µa I IL Input Current (Low) = V µa Note : Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note :.6µF is the minimum required C FLY capacitance for rated output current capability. Depending on the choice of capacitor material, a somewhat higher value of capacitor may be required to attain.6µf over temperature. Note : The LTC74ES6-X is guaranteed to meet performance specifications from C to 7 C. Specifications over the 4 C to 8 C operating temperature range are assured by design, characterization and correlation with statistical process controls. Note 4: Based on long term current density limitations.

3 LTC74-./LTC74- TYPICAL PERFOR A CE CHARACTERISTICS W LTC74-., T A = C unless otherwise noted. OTPT VOLTAGE (V).4... Output Voltage vs Output Current T A = C C OT = µf C FLY = µf = V =.V SPPLY CRRENT (µa) No Load Supply Current vs Supply Voltage I OT = µa C FLY = µf V = T A = 8 C T A = C T A = 4 C SPPLY CRRENT (µa) Supply Current vs V TA = C I OT = µa = V =.V = 4.V OTPT CRRENT (ma) V CONTROL VOLTAGE (V) 74 G 74 G 74 G SHORT-CIRCIT CRRENT (ma) Short-Circuit Current vs Supply Voltage T A = C C FLY = µf Load Transient Response G4 4. Output Ripple EFFICIENCY (%) Efficiency vs Load Current TA = C 9 = V 8 C FLY = µf.. LOAD CRRENT (ma) 74 G Start-p Time I OT ma to ma ma/div AC COPLED mv/div AC COPLED mv/div V/DIV V/DIV = V µs/div 74 G7 C OT = µf = V µs/div 74 G8 C OT = µf I OT = ma = V µs/div 74 G9 C OT = µf

4 LTC74-./LTC74- TYPICAL PERFOR A CE CHARACTERISTICS W LTC74-, T A = C unless otherwise noted. Output Voltage vs Output Current No Load Supply Current vs Supply Voltage Supply Current vs V OTPT VOLTAGE (V) T A = C C OT = µf C FLY = µf = V =.7V SPPLY CRRENT (µa) I OT = µa C FLY = µf V = T A = 8 C T A = 4 C T A = C SPPLY CRRENT (µa) T A = C I OT = µa =.V =.7V =.V OTPT CRRENT (ma) V CONTROL VOLTAGE (V) 74- G 74 G 74 G SHORT-CIRCIT CRRENT (ma) Short-Circuit Current vs Supply Voltage T A = C C FLY = µf G EFFICIENCY (%) Efficiency vs Load Current VIN = V 9 T A = C 8 C FLY = µf LOAD CRRENT (ma) 74- G Load Transient Response Output Ripple Start-p Time I OT ma to ma ma/div AC COPLED mv/div AC COPLED mv/div V/DIV V/DIV = V µs/div 74 G6 C OT = µf = V µs/div 74 G7 C OT = µf I OT = ma = V µs/div 74 G8 C OT = µf 4

5 LTC74-./LTC74- TYPICAL PERFOR A CE CHARACTERISTICS W LTC74-.. LTC74-, T A = C unless otherwise noted. EFFICIENCY (%) Efficiency vs Supply Voltage LTC74-. I OT = ma LTC74- I OT = ma T A = C C FLY = µf OSCILLATOR FREQENCY (khz) Oscillator Frequency vs Supply Voltage T A = 8 C T A = C T A = 4 C THRESHOLD VOLTAGE (V) V Threshold Voltage vs Supply Voltage T A = 4 C T A = C T A = 8 C G9 74 G 74 G PI F CTIO S (Pin ): Regulated Output Voltage. For best performance, should be bypassed with a 6.8µF (min) low ESR capacitor as close as possible to the pin. (Pin ): Ground. Should be tied to a ground plane for best performance. (Pin ): Active Low Shutdown Input. A low on disables the LTC74. must not be allowed to float. C (Pin 4): Flying Capacitor Negative Terminal. (Pin ): Input Supply Voltage. should be bypassed with a 6.8µF (min) low ESR capacitor. C + (Pin 6): Flying Capacitor Positive Terminal. SI PLIFIED W BLOCK DIAGRA W * C + C OT µf C FLY µf + COMP CONTROL C C IN µf V REF *CHARGE PMP SHOWN IN PHASE, THE CHARGING PHASE. PHASE IS ALSO THE SHTDOWN PHASE 74 BD

6 LTC74-./LTC74- APPLICATIO S I FOR ATIO Operation (Refer To Block Diagram) The LTC74 uses a switched-capacitor charge pump to boost to a regulated output voltage. Regulation is achieved by sensing the output voltage through an internal resistor divider and enabling the charge pump when the divided output drops below the lower trip point of COMP. When the charge pump is enabled, a two-phase nonoverlapping clock activates the charge pump switches. The flying capacitor is charged to on phase one of the clock. On phase two of the clock it is stacked in series with and connected to. This sequence of charging and discharging the flying capacitor continues at a free running frequency of 6kHz (typ). Once the attenuated output voltage reaches the upper trip point of COMP, the charge pump is disabled. When the charge pump is disabled the LTC74 draws only µa from thus providing high efficiency under low load conditions. In shutdown mode all circuitry is turned off and the LTC74 draws only leakage current from the supply. Furthermore, is disconnected from. The pin is a CMOS input with a threshold voltage of approximately.8v, but may be driven to a logic level that exceeds. The LTC74 is in shutdown when a logic low is applied to the pin. Since the pin is a high impedance CMOS input, it should never be allowed to float. To ensure that its state is defined, it must always be driven with a valid logic level. Power Efficiency The efficiency (η) of the LTC74 is similar to that of a linear regulator with an effective input voltage of twice the actual input voltage. This results because the input current for a voltage doubling charge pump is approximately twice the output current. In an ideal voltage doubling regulator the power efficiency would be given by: ( )( ) P V I OT OT OT η= = P ( V )( I ) = IN IN OT W V V OT At moderate-to-high output power, the switching losses and quiescent current of the LTC74 are negligible and the expression above is valid. For example, an LTC74- with IN = V, I OT = ma and regulating to V, has a measured efficiency of 8.7%, which is in close agreement with the theoretical 8.% calculation. The LTC74 continues to maintain good efficiency even at fairly light loads because of its inherently low power design. Short-Circuit/Thermal Protection During short-circuit conditions, the LTC74 will draw between ma and 4mA from causing a rise in the junction temperature. On-chip thermal shutdown circuitry disables the charge pump once the junction temperature exceeds approximately C and reenables the charge pump once the junction temperature drops back to approximately 4 C. The LTC74 will cycle in and out of thermal shutdown indefinitely without latchup or damage until the short circuit on is removed. Capacitor Selection The style and value of capacitors used with the LTC74 determine several important parameters such as output ripple, charge pump strength and turn-on time. To reduce noise and ripple, it is recommended that low ESR (<.Ω) capacitors be used for both C IN and C OT. These capacitors should be either ceramic or tantalum and be 6.8µF or greater. Aluminum capacitors are not recommended because of their high ESR. If the source impedance to is very low up to several megahertz, C IN may not be needed. A ceramic capacitor is recommended for the flying capacitor with a value in the range of µf to.µf. Note that a large value flying capacitor (>.µf) will increase output ripple unless C OT is also increased. For very low load applications, C FLY may be reduced to.µf to.47µf. This will reduce output ripple at the expense of maximum output current and efficiency. In order to achieve the rated output current it is necessary to have at least.6µf of capacitance for the flying capacitor. Capacitors of different material lose their capacitance over temperature at different rates. For example, a ceramic capacitor made of X7R material will retain most of its capacitance from 4 C to 8 C, whereas a Z or YV style capacitor will lose considerable capacitance over that 6

7 LTC74-./LTC74- APPLICATIO S I FOR ATIO W range. The capacitor manufacturer s data sheet should be consulted to determine what style and value of capacitor is needed to ensure.6µf at all temperatures. + LTC74-X µf TANTALM µf CERAMIC Output Ripple Low frequency regulation mode ripple exists due to the hysteresis in the sense comparator and propagation delay in the charge pump control circuit. The amplitude and frequency of this ripple are heavily dependent on the load current, the input voltage and the output capacitor size. For large the ripple voltage can become substantial because the increased strength of the charge pump causes fast edges that may outpace the regulation circuitry. Generally the regulation ripple has a sawtooth shape associated with it. A high frequency ripple component may also be present on the output capacitor due to the charge transfer action of the charge pump. In this case the output can display a voltage pulse during the charging phase. This pulse results from the product of the charging current and the ESR of the output capacitor. It is proportional to the input voltage, the value of the flying capacitor and the ESR of the output capacitor. Typical combined output ripple for the LTC74- with = V under maximum load is 6mV P-P using a low ESR µf output capacitor. A smaller output capacitor and/or larger output current load will result in higher ripple due to higher output voltage slew rates. There are several ways to reduce output voltage ripple. For applications requiring higher or lower peak-to-peak ripple, a larger C OT capacitor (µf or greater) is recommended. A larger capacitor will reduce both the low and high frequency ripple due to the lower charging and discharging slew rates, as well as the lower 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 used. To reduce both the low and high frequency ripple, a reasonable compromise is to use a µf to µf tantalum capacitor in parallel with a µf to.µf ceramic capacitor on. An R-C filter may also be used to reduce high frequency voltage spikes (see Figure ). LTC74-X Ω + + µf TANTALM µf TANTALM 74 F Figure. Output Ripple Reduction Techniques In low load or high applications, smaller values for the flying capacitor may be used to reduce output ripple. A smaller flying capacitor (.µf to.47µf) delivers less charge per clock cycle to the output capacitor resulting in lower output ripple. However, with a smaller flying capacitor, the maximum available output current will be reduced along with the efficiency. Note that when using a larger output capacitor the turn on time of the device will increase. Inrush Currents During normal operation will experience current transients in the ma to ma range whenever the charge pump is enabled. However during start-up, inrush currents may approach ma. For this reason it is important to minimize the source impedance between the input supply and the pin. Too much source impedance may result in regulation problems or prevent start-up. ltralow Quiescent Current Regulated Supply The LTC74 contains an internal resistor divider (refer to the Simplified Block Diagram) that typically draws.µa from. During no-load conditions, this internal load causes a droop rate of only mv per second on with C OT = µf. Applying a Hz to Hz, % to % duty cycle signal to the pin ensures that the circuit of Figure comes out of shutdown frequently enough to maintain regulation. Since the LTC74 spends nearly the entire time in shutdown, the no-load quiescent current is approximately ( )(.µa)/(η ). The LTC74 must be out of shutdown for a minimum duration of µs to allow enough time to sense the output voltage and keep it in regulation. A Hz, % duty cycle 7

8 LTC74-./LTC74- APPLICATIO S I FOR ATIO signal will keep in regulation under no-load conditions. As the load current increases, the frequency with which the LTC74 is taken out of shutdown must also be increased. PIN WAVEFORM Figure. ltralow Quiescent Current Regulated Supply SPPLY CRRENT (µa) 6 4 µf. T A = C I OT = µa C FLY = µf W V C + OT LTC74-X C LTC74- LTC F Figure. No-Load Supply Current vs Supply Voltage for the Circuit Shown in Figure 6 4 µf µf LOW I Q MODE (Hz TO Hz, % TO % DTY CYCLE) 74 F Layout Considerations Due to high switching frequency and high transient currents produced by the LTC74, careful board layout is necessary. A true ground plane and short connections to all capacitors will improve performance and ensure proper regulation under all conditions. Figure 4 shows the recommended layout configuration µf µf LTC74-X Figure 4. Recommended Layout µf 74- F4 Thermal Management For higher input voltages and maximum output current, there can be substaintial power dissipation in the LTC74. If the junction temperature increases above approximately C, the thermal shutdown circuitry will automatically deactivate the output. To reduce the maximum junction temperature, a good thermal connection to the PC board is recommended. Connecting the pin (Pin ) to a ground plane and maintaining a solid ground plane under the device on at least two layers of the PC board can reduce the thermal resistance of the package and PC board system to about C/W. 8

9 LTC74-./LTC74- TYPICAL APPLICATIO S Low Power Battery Backup with Autoswitchover and No Reverse Current V µf N448 7k + -CELL NiCd BATTERY µf µf LTC74-. LTC-. µf =.V I OT ma I OT ma BACKP.M k 6 LTC4 8 HIGH = BACKP MODE k M 74 TA SB Port to Regulated V Power Supply µf LTC74- µf µf V ±4% ma 74 TA6 9

10 LTC74-./LTC74- TYPICAL APPLICATIO S V, ma Step-p Generator from V µf V µf LTC74- V ma µf LTC74- µf ON/OFF 74 TA7 Lithium-Ion Battery to V White or Blue LED Driver µf V TO 4.4V Li-Ion BATTERY µf µf Ω Ω Ω LTC74- ON/OFF 74 TA8.V and V Step-p Generator from V µf µf.v I. + I ma V µf LTC74-. µf LTC74- µf V.I. + I η (I. + 4I ) ON/OFF 74 TA9

11 LTC74-./LTC74- PACKAGE DESCRIPTION Dimensions in inches (millimeters), unless otherwise noted. S6 Package 6-Lead Plastic SOT- (LTC DWG # -8-64).8. (..8) (NOTE ).6. (..8)..7 (.9.69).9 (.74) REF.. (..6).9 (.7) REF.9.4 (..7).. (.4.).9. (.4.8) (NOTE ) NOTE:. DIMENSIONS ARE IN MILLIMETERS. DIMENSIONS ARE INCLSIVE OF PLATING. DIMENSIONS ARE EXCLSIVE OF MOLD FLASH AND METAL BRR 4. MOLD FLASH SHALL NOT EXCEED.4mm. PACKAGE EIAJ REFERENCE IS SC-74A (EIAJ)...9. (.4.) (..) SIX PLACES (NOTE ) S6 SOT- 898 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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.

12 LTC74-./LTC74- TYPICAL APPLICATIO Low Power Battery Backup with Autoswitchover and No Reverse Current µf Si44DY V µf N448 7k + -CELL NiCd BATTERY µf LTC74- µf = V I OT ma BAT4C.4M k 6 LTC4 8 k M 74 TA RELATED PARTS PART NMBER DESCRIPTION COMMENTS LT4 High Power Doubler Charge Pump p to ma Output, =.V to V, SO-8 Package LTC44 Charge Pump Inverter with Shutdown = V to 8V, V to V Supply LTC6 V, ma Flash Memory Prog. Supply Regulated V ±% Output, I Q = µa LTC4/LTC Buck/Boost Charge Pumps with I Q = 6µA ma Output at V,.V or V; V to V Input LTC6 Micropower V Charge Pump I Q = µa, p to ma Output, = V to V LTC7-/LTC7-. Micropower V/.V Doubler Charge Pumps I Q = 6µA, p to ma Output LTC Micropower V Doubler Charge Pump I Q = 6µA, p to ma Output LT6 Step-p Switching Regulator in SOT- I Q = µa, =.V to V, p to 4V Output LTC68 Low Noise Doubler Charge Pump Output Noise = 6µV RMS,.V to.v Output Linear Technology Corporation 6 McCarthy Blvd., Milpitas, CA (48)4-9 FAX: (48) f LT/TP 4 4K PRINTED IN SA LINEAR TECHNOLOGY CORPORATION 999