LTC1928-5 Doubler Charge Pump with Low Noise Linear Regulator in ThinSOT U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO Low Output Noise: 90µVRMS (100kHz BW) Fixed Output Voltage: 5V Input Voltage Range: 2.7V to 4.4V No Inductors Required Uses Small Ceramic Capacitors Output Current Up to 30mA 550kHz Switching Frequency Low Operating Current: 190µA Low Shutdown Current: 4µA Internal Thermal Shutdown and Current Limiting Low Profile (1mm) ThinSOTTM Package U APPLICATIO S ■ ■ ■ ■ ■ ■ ■ ■ 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. 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. 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 Wireless PCMCIA Cards Portable Medical Instruments Low Power Data Acquisition Remote Transmitters White LED Drivers GaAs Switches The LTC1928-5 is short-circuit and overtemperature protected. The part is available in a 6-pin low profile (1mm)ThinSOT package. , LTC and LT are registered trademarks of Linear Technology Corporation ThinSOT is a trademark of Linear Technology Corporation. U 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 = 5V TA = 25°C 19285 TA01 1 LTC1928-5 W W W AXI U U ABSOLUTE RATI GS U U W PACKAGE/ORDER I FOR ATIO (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 ORDER PART NUMBER TOP VIEW VIN 1 6 CN/SHDN GND 2 5 CP VOUT 3 4 CPO LTC1928ES6-5 S6 PART MARKING S6 PACKAGE 6-LEAD PLASTIC SOT-23 TJMAX = 125°C, θJA = 230°C/ W LTKT Consult factory for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. VIN = 3V, CFLY = 0.47µF, COUT, CCPO, CIN = 4.7µF unless otherwise specified. PARAMETER CONDITIONS MIN VIN Operating Voltage TYP UNITS 4.4 V IVIN Shutdown Current SHDN = 0V (Note 5) ● 4 8 µA IVIN Operating Current IOUT = 0mA, Burst ModeTM Operation ● 190 330 µA Regulated Output Voltage IOUT = 1mA ● 5 5.1 ● 2.7 MAX 4.9 ±50 VOUT Temperature Coefficient Charge Pump Oscillator Frequency IOUT > 500µA, VIN = 2.7V to 4.4V ● CPO Output Resistance VIN = 2.7V, IOUT = 10mA VIN = 4.4V, IOUT = 10mA ● ● VOUT Dropout Voltage (Note 3) IOUT = 10mA, VOUT = 5V ● 480 V ppm 550 620 kHz 17 14 30 24 Ω Ω 100 mV 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 ● 4 20 mV VOUT Load Regulation IOUT = 1mA to 10mA IOUT = 1mA to 30mA (Note 4) ● 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 ● ● 160 100 400 300 Ω Ω CN/SHDN Input Threshold VIN = 2.7V to 4.4V (Note 5) ● 0.15 0.5 1.6 V CN/SHDN Input Current CN/SHDN = 0V (Note 5) ● –1 –3 –6 µA Burst Mode is a trademark of Linear Technology Corporation. Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. 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. 2 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). LTC1928-5 ELECTRICAL CHARACTERISTICS Note 4: Operating conditions are limited by maximum junction temperature. The regulated output specification will not apply for all possible combinations of input voltage and output current. When operating at maximum input voltage, the output current range may be limited. When operating at maximum output current, the input voltage range may be limited. Note 5: CN/SHDN must be driven with a source impedance of at least 100Ω (RSOURCE) to prevent damage to the part. This pin is multiplexed and may be connected through a low switch impedance to VIN. There may be a large amount of current (VIN/RSOURCE) until the shutdown state occurs after which the charge pump switches at CN/SHDN become high impedance and the current will fall to < 8µA. U W TYPICAL PERFOR A CE CHARACTERISTICS Min and Max VCPO vs VIN 9 TA = 25°C CFLY = 0.47µF 30 IOUT = 10mA VOUT Transient Response 10 TA = 25°C ∆VOUT (mV) CPO Output Resistance vs VIN 35 8 VCPO = 2(VIN) 7 VCPO (V) RCPO (Ω) 25 20 (A) 6 (B) IOUT (mA) 4 10 3 3.0 3.5 VIN (V) 4.0 2.5 4.5 3.0 3.5 VIN (V) TA = 25°C VIN = 3V VOUT = 5V COUT = 4.7µF –5 15 15 5 2.5 0 –10 VCPO = 1.45(VIN) 5 5 4.0 10 5 0 4.5 0 50 100 150 200 TIME (µs) 250 (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 Shutdown to Enable Timing (Figure 5) 300 19285 G03 Enable to Shutdown Timing (Figure 5) VOUT Voltage vs Temperature 0 2 5 5 4 4 3 2 1 0 TA = 25°C VIN = 3V VOUT = 5V IOUT = 10mA COUT = CCPO = 4.7µF 200µs/DIV 19285 G04 5.030 VIN = 3V IOUT = 10mA 0 VOUT VOLTAGE (V) SHDN (V) 2 VOUT (V) VOUT (V) SHDN (V) 5.040 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 3 LTC1928-5 U W TYPICAL PERFOR A CE CHARACTERISTICS Operating Current vs VIN (No Load) 260 Efficiency vs Supply Voltage 100 TA = 25°C TA = 25°C IOUT = 15mA CFLY = 0.47µF 90 180 160 OUTPUT VOLTAGE (V) 200 80 70 60 140 4.989 4.988 4.987 4.986 4.985 4.984 50 120 100 2.5 TA = 25°C VIN = 3V CFLY = 0.47µF 4.900 220 EFFICIENCY (%) OPERATING CURRENT (µA) 240 Output Voltage vs Output Current 4.901 4.983 4.982 40 3.0 3.5 VIN (V) 4.0 0 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 SUPPLY VOLTAGE (V) 4.5 19285 G07 5 10 15 20 25 30 OUTPUT CURRENT (mA) W CFLY 0.47µF CIN 4.7µF 1 6 CN/SHDN CHARGE PUMP AND SLEW CONTROL 4 CPO CCPO 4.7µF – VIN 5 ENB CLK B + + POR/ SHDN CONTROL BURST 550kHz OSCILLATOR – SD + – VOUT 3 VREF = 1.235V COUT 4.7µF 160Ω SD 2 19285 BD GND 4 40 19285 G09 19285 G08 BLOCK DIAGRA CP 35 LTC1928-5 U U U 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. 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. 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. U W U U 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. Generally, 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 internal 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). 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. 5 LTC1928-5 W U U VCPO U RCPO APPLICATIONS INFORMATION RDROPOUT + + 2V IN – – VOUT VDROPOUT CCPO IOUT 19285 F02 Figure 2. Equivalent Circuit 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 ≥ 2 µF and a spike reducing resistor of 2.2Ω may be required between VIN and the supply. 6 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. Shutdown 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 V IN 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. LTC1928-5 U U W U APPLICATIONS INFORMATION Power-On Reset General Layout Considerations 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. 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. Thermal Considerations Measuring Output Noise 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 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. 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. BNC CABLES OR COUPLERS BATTERY OR LOW NOISE DC POWER SUPPLY COUPLING CAPACITOR LTC1928 VOUT DEMO BOARD + 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 VRIPPLE < 800µVP-P 5V VIN 3V COUT 4.7µF LTC1928-5 3 2 1 CIN 4.7µF VOUT CPO GND CP VIN CN/SHDN ADDITIONAL LDO 4 5 6 CFLY 0.47µF CCPO 4.7µF IN OUT 3.3V GND 10µF 19285 F04 Figure 4. LTC1928-5, External Load on CPO, No Shutdown State 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. 7 LTC1928-5 U U W U APPLICATIONS INFORMATION VIN 2.7V TO 4.4V CIN 4.7µF LTC1928-5 1 5 CFLY 0.47µF 6 VIN VOUT CP CPO CN/SHDN GND 3 VRIPPLE < 800µVP-P 4 2 CCPO 4.7µF 19285 F05 100Ω 2N7002 5V COUT 4.7µF SHDN Figure 5. Low Noise 5V Supply with Shutdown U PACKAGE DESCRIPTION S6 Package 6-Lead Plastic SOT-23 SOT-23 (Original) SOT-23 (ThinSOT) A .90 – 1.45 (.035 – .057) 1.00 MAX (.039 MAX) A1 .00 – 0.15 (.00 – .006) .01 – .10 (.0004 – .004) A2 .90 – 1.30 (.035 – .051) .80 – .90 (.031 – .035) L .35 – .55 (.014 – .021) .30 – .50 REF (.012 – .019 REF) (Reference LTC DWG # 05-08-1634) (Reference LTC DWG # 05-08-1636) 2.80 – 3.10 (.110 – .118) (NOTE 3) .20 (.008) A DATUM ‘A’ A2 2.60 – 3.00 1.50 – 1.75 (.102 – .118) (.059 – .069) (NOTE 3) L NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS MILLIMETERS 2. DIMENSIONS ARE IN (INCHES) .09 – .20 (.004 – .008) (NOTE 2) 1.90 (.074) REF PIN ONE ID A1 3. DRAWING NOT TO SCALE 4. DIMENSIONS ARE INCLUSIVE OF PLATING 5. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR 6. MOLD FLASH SHALL NOT EXCEED .254mm 7. PACKAGE EIAJ REFERENCE IS: SC-74A (EIAJ) FOR ORIGINAL JEDEL MO-193 FOR THIN .95 (.037) REF .25 – .50 (.010 – .020) (6PLCS, NOTE 2) S6 SOT-23 0401 RELATED PARTS PART NUMBER DESCRIPTION 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 8 Linear Technology Corporation COMMENTS 1928f LT/TP 0601 2K • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com LINEAR TECHNOLOGY CORPORATION 2000