LTC1928-5 Doubler Charge Pump with Low Noise Linear Regulator in ThinSOT FEATURES DESCRIPTION Low Output Noise: 90µVRMS (100kHz BW) nn Fixed Output Voltage: 5V nn Input Voltage Range: 2.7V to 4.4V nn No Inductors Required nn Uses Small Ceramic Capacitors nn Output Current Up to 30mA nn 550kHz Switching Frequency nn Low Operating Current: 190µA nn Low Shutdown Current: 4µA nn Internal Thermal Shutdown and Current Limiting nn Low Profile (1mm) ThinSOT™ Package The LTC®1928-5 is a doubler charge pump with an internal low noise, low dropout (LDO) linear regulator. The part is designed to provide a low noise boosted supply voltage for powering noise sensitive devices such as high frequency VCOs in wireless applications. nn An internal charge pump converts a 2.7V to 4.4V input to a boosted output, while the internal LDO regulator converts the boosted voltage to a low noise regulated output. The regulator is capable of supplying up to 30mA of output current. Shutdown reduces the supply current to <8µA, removes the load from VIN by disabling the regulator and discharges VOUT to ground through a 200Ω switch. APPLICATIONS The LTC1928-5 LDO regulator is stable with only 2µF on the output. Small ceramic capacitors can be used, reducing PC board area. VCO Power Supplies for Cellular Phones 2-Way Pagers nn Wireless PCMCIA Cards nn Portable Medical Instruments nn Low Power Data Acquisition nn Remote Transmitters nn White LED Drivers nn GaAs Switches nn nn The LTC1928-5 is short-circuit and overtemperature protected. The part is available in a 6-pin low profile (1mm) ThinSOT package. L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and ThinSOT and Burst Mode are trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATION Output Noise (BW = 10Hz to 2.5MHz) LTC1928-5 VIN 2.7V TO 4.4V 1 4.7µF 0.47µF 5 6 VIN CP VOUT CPO CN/SHDN GND 5V 3 4 2 VOUT 4.7µF 4.7µF VOUT 200µV/DIV 19285 F01 Figure 1. Low Noise 5V Power Supply CCPO = COUT = 4.7µF 100µs/DIV IOUT = 10mA VIN = 3V VOUT = 5A TA = 25°C 19285 TA01 19285fa For more information www.linear.com/LTC 1928-5 1 LTC1928-5 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) VIN to Ground................................................ –0.3V to 5V VOUT Voltage............................................ –0.3V to 5.25V CPO to Ground...........................................................10V CN/SHDN to Ground...................... –0.3V to (VIN + 0.3V) VOUT Short-Circuit Duration.............................. Indefinite IOUT.........................................................................40mA Operating Temperature Range (Note 2)....–40°C to 85°C Maximum Junction Temperature ......................... 125°C Storage Temperature Range................... –65°C to 150°C Lead Temperature (Soldering, 10 sec).................... 300°C TOP VIEW VIN 1 6 CN/SHDN GND 2 5 CP VOUT 3 4 CPO S6 PACKAGE 6-LEAD PLASTIC SOT-23 TJMAX = 125°C, θJA = 230°C/W ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LTC1928ES6-5#PBF LTC1928ES6-5#TRPBF LTKT 6-Lead Plastic SOT-23 –40°C to 85°C Consult LTC Marketing for parts specified with wider operating temperature ranges. Consult LTC Marketing for information on nonstandard 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. VIN = 3V, CFLY = 0.47µF, COUT, CCPO, CIN = 4.7µF unless otherwise specified. PARAMETER CONDITIONS VIN Operating Voltage MIN l TYP 2.7 MAX 4.4 UNITS V IVIN Shutdown Current SHDN = 0V (Note 5) l 4 8 µA IVIN Operating Current IOUT = 0mA, Burst Mode™ Operation l 190 330 µA Regulated Output Voltage IOUT = 1mA l 4.9 5 5.1 V Charge Pump Oscillator Frequency IOUT > 500µA, VIN = 2.7V to 4.4V l 480 550 620 kHz CPO Output Resistance VIN = 2.7V, IOUT = 10mA VIN = 4.4V, IOUT = 10mA l l 17 14 30 24 Ω Ω VOUT Dropout Voltage (Note 3) IOUT = 10mA, VOUT = 5V l 100 mV VOUT Temperature Coefficient ±50 ppm VOUT Enable Time RLOAD = 2k 0.6 ms VOUT Output Noise Voltage IOUT = 10mA, 10Hz ≤ f ≤ 100kHz IOUT = 10mA, 10Hz ≤ f ≤ 2.5MHz 90 800 µVRMS µVP-P VOUT Line Regulation VIN = 2.7V to 4.4V, IOUT = 0 l 4 20 mV VOUT Load Regulation IOUT = 1mA to 10mA IOUT = 1mA to 30mA (Note 4) l 2 4 10 mV mV VOUT Shutdown Resistance CN/SHDN = 0V (Note 5) VIN = 2.7V, Resistance Measured to Ground VIN = 4.4V, Resistance Measured to Ground l l 160 100 400 300 Ω Ω 19285fa 2 For more information www.linear.com/LTC 1928-5 LTC1928-5 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 3V, CFLY = 0.47µF, COUT, CCPO, CIN = 4.7µF unless otherwise specified. CN/SHDN Input Threshold VIN = 2.7V to 4.4V (Note 5) l 0.15 0.5 1.6 V CN/SHDN Input Current CN/SHDN = 0V (Note 5) l –1 –3 –6 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 LTC1928ES6-5 is guaranteed to meet performance specifications from 0°C to 70°C. Specifications over the –40°C to 85°C operating temperature range are assured by design, characterization and correlation with statistical process controls. Note 3: Dropout voltage is the minimum input/output voltage required to maintain regulation at the specified output current. In dropout the output voltage will be equal to: VCPO – VDROPOUT (see Figure 2). TYPICAL PERFORMANCE CHARACTERISTICS CPO Output Resistance vs VIN TA = 25°C CFLY = 0.47µF 30 IOUT = 10mA VOUT Transient Response 10 TA = 25°C VCPO = 2(VIN) 7 15 (A) 6 (B) 5 4 3 3.0 3.5 VIN (V) 4.0 2.5 4.5 3.0 3.5 VIN (V) 0 4.0 10 5 0 4.5 Shutdown to Enable Timing (Figure 5) 5 4 4 2 1 0 TA = 25°C VIN = 3V VOUT = 5V IOUT = 10mA COUT = CCPO = 4.7µF 200s/DIV 19285 G04 100 150 200 TIME (µs) 250 300 5.030 VOUT Voltage vs Temperature VIN = 3V IOUT = 10mA 0 VOUT VOLTAGE (V) SHDN (V) 2 5 VOUT (V) VOUT (V) SHDN (V) 5.040 3 50 19285 G03 Enable to Shutdown Timing (Figure 5) 0 0 (A) THE MAXIMUM GENERATED NO LOAD CPO VOLTAGE (B) THE MINIMUM ALLOWABLE CPO VOLTAGE, AT FULL LOAD, TO ENSURE THAT THE LDO IS NOT DISABLED 19285 G02 19285 G01 2 TA = 25°C VIN = 3V VOUT = 5V COUT = 4.7µF –5 15 10 5 2.5 5 –10 VCPO = 1.45(VIN) IOUT (mA) VCPO (V) 20 ∆VOUT (mV) 8 25 RCPO (Ω) Min and Max VCPO vs VIN 9 35 3 2 1 0 NO LOAD TA = 25°C VIN = 3V VOUT = 5V COUT = 4.7µF 5.020 5.010 5.000 4.990 4.980 –50 –25 1ms/DIV 19285 G05 50 25 75 0 TEMPERATURE (°C) 100 125 19285 G06 19285fa For more information www.linear.com/LTC 1928-5 3 LTC1928-5 TYPICAL PERFORMANCE CHARACTERISTICS Operating Current vs VIN (No Load) 260 Efficiency vs Supply Voltage 100 TA = 25°C TA = 25°C IOUT = 15mA CFLY = 0.47µF 90 200 180 160 80 70 60 140 100 2.5 3.0 3.5 VIN (V) 4.0 4.5 40 4.989 4.988 4.987 4.986 4.985 4.984 50 120 TA = 25°C VIN = 3V CFLY = 0.47µF 4.900 OUTPUT VOLTAGE (V) 220 EFFICIENCY (%) OPERATING CURRENT (µA) 240 Output Voltage vs Output Current 4.901 4.983 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 SUPPLY VOLTAGE (V) 19285 G07 4.982 0 5 10 15 20 25 30 OUTPUT CURRENT (mA) 19285 G08 35 40 19285 G09 PIN FUNCTIONS VIN (Pin 1): Input Voltage, 2.7V to 4.4V. VIN should be bypassed with a ≥2µF low ESR capacitor as close to the pin as possible for best performance. A minimum capacitance value of 0.1µF is required. GND (Pin 2): System Ground. CP (Pin 5): Flying Capacitor Positive Input. CN/SHDN (Pin 6): Flying Capacitor Negative Input and SHDN. When this pin is pulled to ground through a 100Ω resistor, the part will go into shutdown within approximately 30µs. VOUT (Pin 3): Low Noise Regulated Output Voltage. VOUT should be bypassed with a ≥2µF low ESR capacitor as close to the pin as possible for best performance. The VOUT voltage is internally set to 5V. CPO (Pin 4): Boosted Unregulated Voltage. Approximately 1.95VIN at low loads. Bypass with a ≥2µF low ESR capacitor. 19285fa 4 For more information www.linear.com/LTC 1928-5 LTC1928-5 BLOCK DIAGRAM CFLY 0.47µF CP CIN 4.7µF 1 6 CN/SHDN CHARGE PUMP AND SLEW CONTROL 4 ENB CPO CCPO 4.7µF – VIN 5 CLK B + POR/ SHDN CONTROL BURST 550kHz OSCILLATOR + – SD + – VOUT 3 VREF = 1.235V COUT 4.7µF 160Ω SD 2 19285 BD GND APPLICATIONS INFORMATION Operation The LTC1928-5 uses a switched-capacitor charge pump to generate a CPO voltage of approximately 2VIN. CPO powers an internal low dropout linear regulator that supplies a regulated output at VOUT. Internal comparators are used to sense CPO and VIN voltages for power-up conditioning. The output current is sensed to determine the charge pump operating mode. A trimmed internal bandgap is used as the voltage reference and a trimmed internal oscillator is used to control the charge pump switches. The charge pump is a doubler configuration that uses one external flying capacitor. When enabled, a 2-phase nonoverlapping clock controls the charge pump switches. At start-up, the LDO is disabled and the load is removed from CPO. When CPO reaches 1.75VIN the LDO is enabled. If CPO falls below 1.45VIN the LDO will be disabled. Gen- erally, the charge pump runs open loop with continuous clocking for low noise. If CPO is greater than 1.95VIN and IOUT is less than 200µA, the charge pump will operate in Burst Mode operation for increased efficiency but slightly higher output noise. In Burst Mode operation, the clock is disabled when CPO reaches 1.95VIN and enabled when CPO droops by about 150mV. The switching frequency is precisely controlled to ensure that the frequency is above 455kHz and at the optimum rate to ensure maximum efficiency. The switch edge rates are also controlled to minimize noise. The effective output resistance at CPO is dependent on the voltage at VIN, CPO, the flying capacitor value CFLY and the junction temperature. A low ESR capacitor of ≥2µF should be used at CPO for minimum noise. The LDO is used to filter the ripple on CPO and to set an output voltage independent of CPO. VOUT is set by an in19285fa For more information www.linear.com/LTC 1928-5 5 LTC1928-5 APPLICATIONS INFORMATION ternal reference and resistor divider. The LDO requires a capacitor on VOUT for stability and improved load transient response. A low ESR capacitor of ≥2µF should be used. Maximum IOUT Calculations The maximum available current can be calculated based on the open circuit CPO voltage, the dropout voltage of the LDO and the effective output resistance of the charge pump. The open circuit CPO voltage is approximately 2VIN (see Figure 2). RCPO VCPO RDROPOUT + + 2V IN – – VOUT VDROPOUT IOUT CCPO 19285 F02 Figure 2. Equivalent Circuit Example: VIN = 3V VOUT = 5V RCPO = 30Ω Maximum unloaded CPO voltage = 2VIN = 6V VDROPOUT(MAX) = 100mV IOUT(MAX)= (2VIN – VDROPOUT(MAX) – VOUT)/RCPO = (6V – 0.1V – 5V)/30Ω = 30mA VCPO must be greater than 1.45VIN = 4.35V. To confirm this, calculate VCPO: VCPO = 6V – (30mA • 30Ω) = 5.1V For minimum noise applications the LDO must be kept out of dropout to prevent CPO noise from coupling into VOUT. External CPO Loading The CPO output can drive an external load (for example, an LDO). The current required by this additional load will reduce the available current from VOUT. If the external load requires 1mA, the available current at VOUT will be reduced by 1mA. Short-Circuit and Thermal Protection VOUT can be shorted to ground indefinitely. Internal circuitry will limit the output current. If the junction temperature exceeds 150°C the part will shut down. Excessive power dissipation due to heavy loads will also cause the part to shut down when the junction temperature exceeds 150°C. The part will become enabled when the junction temperature drops below 140°C. If the fault conditions remain in place, the part will cycle between the shutdown and enabled states. Capacitor Selection For best performance it is recommended that low ESR ceramic capacitors be used to reduce noise and ripple. COUT must be ≥2µF and CCPO must be equal to or greater than COUT. CIN is dependent on the input power supply source impedance. The charge pump demands large instantaneous currents which may induce ripple onto a common voltage rail. CIN should be ≥2µF and a spike reducing resistor of 2.2Ω may be required between VIN and the supply. A low ESR ceramic capacitor is recommended for the flying capacitor CFLY with a value of 0.47µF. At low load or high VIN a smaller capacitor could be used to reduce ripple on CPO which would reflect as lower ripple on VOUT. If a minimum enable time is required, the CPO output filter capacitor should be at least 2× the VOUT filter capacitor. When the LDO is first enabled, the CPO capacitor will dump a large amount of charge into the VOUT capacitor. If the drop in the CPO voltage falls below 1.45VIN the LDO will be disabled and the CPO voltage will be required to charge up to 1.75VIN to enable the LDO. The resulting cycling extends the enable time. Output Ripple The output ripple on CPO includes a spike component from the charge pump switches and a droop component which is dependent on the load current and the value of C3. The charge pump has been carefully designed to minimize the spike component, however, low ESR capacitors are essential to reduce the remaining spike energy effect on the CPO voltage. CCPO should be increased for high load currents to minimize the droop component. Ripple components on CPO are greatly reduced at VOUT by the LDO, however, COUT should also be a low ESR capacitor to improve filtering of the CPO noise. 19285fa 6 For more information www.linear.com/LTC 1928-5 LTC1928-5 APPLICATIONS INFORMATION Shutdown device dissipates the majority of its heat through its pins, especially GND (Pin 2). Thermal resistance to ambient can be optimized by connecting GND to a large copper region on the PCB, which serves as a heat sink. Applications that operate the LTC1928-5 near maximum power levels should maximize the copper area at all pins except CP and CN/SHDN and ensure that there is some airflow over the part to carry away excess heat. When CN/SHDN = 0V, the part will be in shutdown, the supply current will be <8µA and VOUT will be shorted to ground through a 160Ω switch. In addition, CPO will be high impedance and disconnected from VIN and CN/SHDN. Shutdown is achieved by internally sampling the CN/SHDN pin for a low voltage. Time between shutdown samples is about 30µs. During the sample time the charge pump switches are disabled and CN/SHDN must be pulled to ground within 400ns. A resistor value between 100Ω and 1k is recommended. Parasitic lead capacitance should be minimized on the CN/SHDN pin. General Layout Considerations Due to the high switching frequency and high transient currents produced by the device, careful board layout is a must. A clean board layout using a ground plane and short connections to all capacitors will improve noise performance and ensure proper regulation. Power-On Reset Measuring Output Noise Upon initial power-up, a power-on reset circuit ensures that the internal functions are correctly initialized. Once VIN reaches about 1V, the power-on reset circuit will enable the part as long as the CN/SHDN pin is not pulled low. Measuring the LTC1928 low noise levels requires care. Figure 3 shows a test setup for taking the measurement. Good connection and signal handling technique should yield about 800µVP-P over a 2.5MHz bandwidth. The noise measurement involves AC-coupling the LTC1928 output into the test setup’s input and terminating this connection with 50Ω. Coaxial connections must be maintained to preserve measurement integrity. Thermal Considerations The power handling capability of the device will be limited by the maximum rated junction temperature (125°C). The device dissipation PD = IOUT(2VIN – VOUT) + VIN(2mA). The BNC CABLES OR COUPLERS BATTERY OR LOW NOISE DC POWER SUPPLY LTC1928 VOUT DEMO BOARD COUPLING CAPACITOR + CONNECT BNC AND RLOAD GROUND TO THE OUTPUT CAPACITOR GROUND TERMINAL – R* RLOAD PREAMP 1822 INPUT BANDWIDTH FILTER 10× OSCILLOSCOPE R* PLACE BANDWIDTH FILTER COMPONENTS IN SHIELDED BOX WITH COAXIAL CONNECTORS R* PLACE COUPLING CAPACITOR IN SHIELDED BOX WITH COAXIAL CONNECTOR *50Ω TERMINATIONS HP-11048C OR EQUIVALENT NOTE: KEEP BNC CONNECTIONS AS SHORT AS POSSIBLE 19285 F03 Figure 3. LTC1928-5 Noise Measurement Test Setup 5V VIN 3V VRIPPLE < 800µVP-P COUT 4.7µF 3 2 1 CIN 4.7µF LTC1928-5 VOUT CPO GND CP VIN CN/SHDN ADDITIONAL LDO 4 5 6 CFLY 0.47µF CCPO 4.7µF IN OUT GND 3.3V 10µF 19285 F04 Figure 4. LTC1928-5, External Load on CPO, No Shutdown State 19285fa For more information www.linear.com/LTC 1928-5 7 LTC1928-5 PACKAGE DESCRIPTION Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. S6 Package 6-Lead Plastic TSOT-23 (Reference LTC DWG # 05-08-1636) 0.62 MAX 2.90 BSC (NOTE 4) 0.95 REF 1.22 REF 3.85 MAX 2.62 REF 1.4 MIN 2.80 BSC 1.50 – 1.75 (NOTE 4) PIN ONE ID RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR 0.30 – 0.45 6 PLCS (NOTE 3) 0.95 BSC 0.80 – 0.90 0.20 BSC 0.01 – 0.10 1.00 MAX DATUM ‘A’ 0.30 – 0.50 REF 0.09 – 0.20 (NOTE 3) NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. DRAWING NOT TO SCALE 3. DIMENSIONS ARE INCLUSIVE OF PLATING 4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR 5. MOLD FLASH SHALL NOT EXCEED 0.254mm 6. JEDEC PACKAGE REFERENCE IS MO-193 1.90 BSC S6 TSOT-23 0302 19285fa 8 For more information www.linear.com/LTC 1928-5 LTC1928-5 REVISION HISTORY REV DATE DESCRIPTION A 09/15 Revised package drawing. PAGE NUMBER 8 19285fa 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 itsinformation circuits as described herein will not infringe on existing patent rights. For more www.linear.com/LTC 1928-5 9 LTC1928-5 TYPICAL APPLICATION VIN 2.7V TO 4.4V CIN 4.7µF 1 5 CFLY 0.47µF 6 LTC1928-5 VIN CP VOUT CPO CN/SHDN GND 3 4 2 VRIPPLE < 800µVP-P CCPO 4.7µF 19285 F05 100Ω 2N7002 5V COUT 4.7µF SHDN Figure 5. Low Noise 5V Supply with Shutdown RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC1550/LTC1551 Low Noise, 900kHz Charge Pump 1mVP-P Typical Ripple, Up to 10mA LT1611 Inverting 1.4MHz Switching Regulator 5V to –5V at 150mA, Low Output Noise LT1613 1.4MHz Boost Switching Regulator in ThinSOT 3.3V to 5V at 200mA, Low Noise PWM Operation LTC1682 Doubler Charge Pump with Low Noise Linear Regulator 60µVRMS Noise, IOUT Up to 80mA, MSOP LTC1754-5 Micropower 5V Charge Pump in ThinSOT IQ = 13µA, IOUT to 50mA, Shutdown LT1761 Series 100mA ThinSOT, Low Noise LDO Regulators 20µA IQ, 20µVRMS Noise, 300mV Dropout LTC3200 Constant Frequency Doubler Charge Pump Low Noise, 5V Output or Adjustable 19285fa 10 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 For more information www.linear.com/LTC 1928-5 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com/LTC1928-5 LT 0915 REV A • PRINTED IN USA LINEAR TECHNOLOGY CORPORATION 2000