LTC1502IS8-3.3

LTC1502-3.3 Single Cell to 3.3V Regulated Charge Pump DC/DC Converter FEATURES s s s s s s s s s s s DESCRIPTIO Input Voltage Range: 0.9V to 1.8V 0.9V Guaranteed Start-Up Voltage Regulated Output Voltage: 3.3V ± 4% Output Current: 10mA (VIN ≥ 1V) No Inductors Shutdown Disconnects Load from VIN Low Operating Current: 40µA Low Shutdown Current: 5µA Short-Circuit and Overtemperature Protected Application Circuit Fits in < 0.125in2 PCB Area Available in 8-Pin MSOP and SO Packages The LTC®1502-3.3 is a quadrupler charge pump DC/DC converter that produces a regulated 3.3V output from a single alkaline cell input. It requires only five small external capacitors—no inductors are required. Low supply current (40µA typical, 5µA in shutdown) and minimal external components make the LTC1502-3.3 ideal for space and power conscious single-cell applications. The total printed circuit board area of the circuit shown below is less than 0.125in2. Forcing the C1 –/SHDN pin low through an external resistive pull-down puts the part into shutdown mode. During shutdown, the internal oscillator is stopped and the load is disconnected from VIN. An internal pull-up current on the C1 –/SHDN pin forces the part back into normal operation once the pull-down resistance is removed. The LTC1502-3.3 is short-circuit protected and survives an indefinite VOUT short to ground. The LTC1502-3.3 is available in 8-pin MSOP and SO packages. , LTC and LT are registered trademarks of Linear Technology Corporation. APPLICATIO S s s s s s Pagers Battery Backup Supplies Portable Electronic Equipment Handheld Medical Instruments Glucose Meters TYPICAL APPLICATIO 1 10µF 1µF 2 8 Single Cell to 3.3V DC/DC Converter 3.5 C2 VOUT 7 C1+ C3 + LTC1502-3.3 6 3 C1–/SHDN C3 – 4 5 GND VIN 10µF 1µF VIN SINGLE CELL NiCd or ALKALINE 1502-3.3 TA01 VOUT = 3.3V IOUT = 10mA 3.4 OUTPUT VOLTAGE (V) 3.3 IOUT = 10mA IOUT = 15mA 10µF 3.2 3.1 PCB LAYOUT FITS IN < 0.125IN2 3.0 0.8 U Output Voltage vs Input Voltage TA = 25°C 1.0 1.4 1.6 1.2 INPUT VOLTAGE (V) 1.8 1502-3.3 TA02 U U 1 LTC1502-3.3 ABSOLUTE MAXIMUM RATINGS (Note 1) VIN to GND .................................................. – 0.3V to 2V VOUT to GND ............................................... – 0.3V to 5V All Other Pins to GND ................................. – 0.3V to 5V VOUT Short-Circuit Duration ............................ Indefinite Storage Temperature Range ................ – 65°C to 150°C Operating Temperature Range Commercial ............................................ 0°C to 70°C Extended Commercial (Note 4) .......... – 40°C to 85°C Industrial ........................................... – 40°C to 85°C Lead Temperature (Soldering, 10 sec)................. 300°C PACKAGE/ORDER INFORMATION TOP VIEW C2 C1+ – C1 /SHDN GND 1 2 3 4 8 7 6 5 VOUT C3 + C3 – VIN ORDER PART NUMBER LTC1502CMS8-3.3 MS8 PART MARKING LTEC C2 1 C1+ 2 C1–/SHDN 3 GND 4 MS8 PACKAGE 8-LEAD PLASTIC MSOP TJMAX = 125°C, θJA = 250°C/ W Consult factory for Military grade parts. ELECTRICAL CHARACTERISTICS The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 0.9V to 1.8V, C1 = C3 = 1µF, CIN = C2 = COUT = 10µF unless otherwise specified. PARAMETER VIN Operating Voltage Minimum VIN Start-Up Voltage VOUT Voltage VIN Operating Current VIN Shutdown Current Output Ripple Efficiency Switching Frequency C1–/SHDN Shutdown Input Threshold C1–/SHDN Shutdown Input Current VOUT Turn-On Time VOUT Short-Circuit Current TA = 0°C to 70°C (Note 2) TA = – 40°C to 85°C (Note 2) IOUT ≤ 3.5mA, 0.9V ≤ VIN ≤ 1.8V IOUT ≤ 10mA, 1V ≤ VIN ≤ 1.8V IOUT = 0mA C1–/SHDN = 0V IOUT = 10mA, VIN = 1.25V VIN = 1V, IOUT = 10mA Oscillator Free-Running C1–/SHDN in Hi-Z Sampling State C1–/SHDN = 0V (Note 3) VIN = 1V, IOUT = 0mA VIN = 1.5V, VOUT Forced to 0V q q CONDITIONS q q q q q q q Note 1: Absolute Maximum Ratings are those values beyond which the life of the device may be impaired. Note 2: Start-up testing is done with a 100kΩ equivalent load on VOUT. Note 3: Currents flowing into the device are positive polarity. Currents flowing out of the device are negative polarity. 2 U U W WW U W TOP VIEW 8 7 6 5 VOUT C3 + C3 – VIN ORDER PART NUMBER LTC1502CS8-3.3 LTC1502IS8-3.3 S8 PART MARKING 150233 502I33 S8 PACKAGE 8-LEAD PLASTIC SO TJMAX = 125°C, θJA = 150°C/ W MIN 0.9 TYP 0.75 MAX 1.8 0.9 1.1 3.43 3.43 90 15 UNITS V V V V V µA µA mVP-P % kHz 3.17 3.17 3.3 3.3 40 5 50 77 500 0.20 – 0.5 0.55 – 2.5 5 20 0.85 –8 V µA ms mA Note 4: Commercial grade specifications are guaranteed over the 0°C to 70°C operating temperature range. In addition, commercial grade specifications are assured over the –40°C to 85°C operating temperature range by design, characterization and correlation with statistical process controls. Industrial grade specifications are guaranteed and tested over the –40°C to 85°C operating temperature range. LTC1502-3.3 TYPICAL PERFOR A CE CHARACTERISTICS No Load Input Current vs Input Voltage 80 IOUT = 0mA TA = 85°C 40 TA = 0°C 20 OUTPUT VOLTAGE (V) INPUT CURRENT (µA) INPUT CURRENT (µA) 60 TA = 70°C TA = 25°C TA = – 40°C 0 0.8 1.0 1.4 1.6 1.2 INPUT VOLTAGE (V) Maximum Start-Up Load Current vs Input Voltage 16 TA = 25°C 100 LOAD CURRENT (mA) 12 EFFICIENCY (%) VIN = 1.25V 60 VIN = 1.5V VIN = 1.8V 40 8 4 0 0.8 1.0 1.4 1.6 1.2 INPUT VOLTAGE (V) Oscillator Frequency vs Input Voltage 700 OSCILLATOR FREQUENCY (kHz) BATTERY LIFE (HOURS) 600 TA = 85°C TA = 70°C TA = 25°C TA = 0°C 500 400 TA = – 40°C 300 0.8 1.0 1.4 1.6 1.2 INPUT VOLTAGE (V) UW 1502-3.3 G01 Shutdown Input Current vs Input Voltage 16 C1–/SHDN = 0V 3.40 Output Voltage vs Output Current TA = 25°C 12 3.35 VIN = 1.5V 3.30 VIN = 1V VIN = 1.8V 8 TA = 70°C 4 TA = 85°C 3.25 TA = – 40°C 1.8 TA = 25°C TA = 0°C 1.8 3.20 0.01 1 10 0.1 OUTPUT CURRENT (mA) 100 1502-3.3 G03 0 0.8 1.0 1.4 1.6 1.2 INPUT VOLTAGE (V) 1502-3.3 G02 Efficiency vs Output Current TA = 25°C VOUT = 3.3V VIN = 1V IOUT 0mA to 10mA 5mA/DIV Load Transient Response 80 VOUT AC COUPLED 50mV/DIV 20 VIN = 1.25V TA = 25°C 200µs/DIV 1502-3.3 G06 1.8 0 0.01 1 0.1 10 OUTPUT CURRENT (mA) 100 1502-3.3 G05 1502-3.3 G04 Calculated Battery Life, Battery = 2400mA • Hr AA Cell 100k Shutdown Waveforms (See Figure 1) 10k VOUT 2V/DIV 1k OFF VCTRL 100 ON VIN = 1.25V RLOAD = 10k TA = 25°C 0.01 0.1 1 10 AVERAGE LOAD CURRENT (mA) 100 100µs/DIV 1502-3.3 G09 1.8 10 0.001 1502-3.3 G07 1502-3.3 G08 3 LTC1502-3.3 PIN FUNCTIONS C2 (Pin 1): Charge Pump 1 (CP1) Output. This pin also serves as the input supply for charge pump 2 (CP2). To ensure proper start-up, the C2 pin must not be externally loaded. Bypass the C2 pin with a ≥ 10µF low ESR capacitor to ground. C1+ (Pin 2): Charge Pump 1 Flying Capacitor Positive Terminal. GND (Pin 4): Ground. Connect to a ground plane for best performance. VIN (Pin 5): Input Supply Voltage. Bypass VIN with a ≥10µF low ESR capacitor to ground. C3 – (Pin 6): Charge Pump 2 (CP2) Flying Capacitor Negative Terminal. C3+ (Pin 7): Charge Pump 2 Flying Capacitor Positive Terminal. VOUT (Pin 8): 3.3V Regulated Output Voltage. VOUT is disconnected from VIN during shutdown. Bypass VOUT with a ≥ 10µF low ESR capacitor to ground. C1–/SHDN (Pin 3): Charge Pump 1 Flying Capacitor Negative Terminal and Shutdown Input. Pulling this pin to ground through a ≈ 100Ω resistor will put the part into shutdown mode. With a high resistance pull-down FET, the series resistor may be eliminated. The external pulldown device must be high impedance for normal operation (see Applications Information). Peak voltage present on this pin is approximately equal to VIN. BLOCK DIAGRAM SHUTDOWN C1–/SHDN C1+ C2 C3– C3+ VIN 5 CIN 2.5µA CP1 400k VIN CP2 8 VOUT COUT COMP3 U2 0.55V HIZ1 CLK1/CLK2 1M SHDN TIMING CONTROL OSCEN U3 C2 VOUT BIAS CONTROL INTERNAL VCC COMP1 4 – + + + – W – + U U U C1 C2 C3 3 2 1 6 7 HIZ2 2.1M COMP2 U4 1.2M 1.2V REF 4 GND 1502-3.3 BD LTC1502-3.3 TEST CIRCUIT 1 10µF 2 C2 VOUT 8 10µF 1µF IOUT 7 C3 + C1+ 1µF LTC1502-3.3 3 6 C1–/SHDN C3 – 4 5 GND VIN 100Ω SWITCH CLOSED FOR SHUTDOWN 10µF VIN 100pF 1502-3.3 TC APPLICATIONS INFORMATION Regulator Operation The LTC1502-3.3 uses a quadrupler charge pump DC/DC converter to produce a boosted output voltage. The quadrupler charge pump consists of two voltage doubler charge pumps (CP1 and CP2 on the Block Diagram) cascaded in series. CP1 doubles the input voltage VIN and the CP1 output voltage is stored on external capacitor C2. The C2 pin also serves as the input for doubler CP2 whose output is stored on the output capacitor COUT. Each doubler is controlled by a two-phase clock which is generated in the Timing Control circuit. On phase one of the clock, the flying capacitors C1 and C3 are charged to their respective input voltages. On phase two each charged flying capacitor is stacked on top of the input voltage and discharged through an internal switch onto its respective output. This sequence of charging and discharging the CP1 and CP2 flying capacitors continues at the free running oscillator frequency (500kHz typ) until the output is in regulation. Regulation is achieved by comparing the divided down output voltage to a fixed voltage reference. The charge pump clocks are disabled when the output voltage is above the desired regulation point set by COMP1. When the output has dropped below the lower trip point of COMP1, the charge pump clocks are turned back on until VOUT is boosted back into regulation. Enhanced Start-Up Enhanced start-up capability is provided by the COMP2 circuitry. COMP2 compares the divided down C2 voltage to the input voltage VIN. The COMP2 output disables the output charge pump CP2 whenever the divided C2 voltage is lower than VIN. The CP2 output is thereby forced into a high impedance state until the voltage on C2 has been raised above VIN (the C2 pin should not be loaded for proper start-up). This allows a higher internal gate drive voltage to be generated (from the C2 pin) before the output (VOUT) is connected to a load. Hysteresis in COMP2 forces CP2 to be turned ON and OFF while COUT is charging up to prevent a lockup condition if C2 droops too low during start-up. By the time the output nears the regulation point, the C2 voltage is well above the lower trip point of COMP2 and CP2 will remain enabled. This method of disabling the output charge pump while an internal boosted gate drive supply is developed allows the part to start up at low voltages with a larger output current load than would otherwise be possible. Shutdown Shutdown is implemented using an external pull-down device on the C1–/SHDN pin. The recommended external pull-down device is an open-drain FET with resistive current limiting (see Figure 1). The pull-down device must sink up to 300µA and pull down below 0.2V to ensure proper shutdown operation, however, the actual series resistance is not critical. The pull-down device must also go into a HiZ state for the LTC1502-3.3 to become active. The timing control circuitry forces the CP1 switches into a high impedance state every 16 clock cycles. The Hi-Z duration is equal to one clock cycle. At the end of the Hi-Z time interval, the voltage on the C1–/SHDN pin is sampled. If the C1–/SHDN pin has been pulled to a logic low state, the part will go into shutdown mode. When the pull-down device is disabled, an internal pull-up current U W U U 5 LTC1502-3.3 APPLICATIONS INFORMATION 1 2 C2 VOUT 8 100Ω ON OFF VCTRL C1+ LTC1502-3.3 3 6 C1–/SHDN C3 – 4 5 GND VIN 7 C3 + Figure 1. Pull-Down Circuitry for Shutdown will force a logic high on the C1–/SHDN pin and put the part back into active mode. If no external pull-down is present during the Hi-Z interval, the internal pull-up current will maintain a logic high on the C1–/SHDN pin thereby keeping the part in active mode. The shutdown feature can be used to prevent charge pump switching during noise sensitive intervals. Since the charge pump oscillator is disabled during shutdown, output switching noise can be eliminated while the external pull-down is active. The LTC1502-3.3 takes between 20µs and 50µs to switch from shutdown to active mode once the pull-down device has been turned off (assuming a 100pF external capacitance to GND on the C1–/SHDN pin). A 100k pull-up resistor from VIN to C1–/SHDN will speed up this transition by a factor of five at the expense of 10µA or so of additional shutdown current. To maintain regulation, a sufficiently large output capacitor must be used to prevent excessive VOUT droop while the charge pump is in shutdown. Also, there must be adequate time for the charge pump to recharge the output capacitor while the part is active. In other words, the average load current must be low enough for the LTC1502-3.3 to maintain a 3.3V output while the part is active. Capacitor Selection For best performance, it is recommended that low ESR capacitors be used for CIN, C2 and COUT to reduce noise and ripple. The CIN, C2 and COUT capacitors should be either ceramic or tantalum and should be 10µF or greater. If the input source impedance is very low (< 0.5Ω), CIN may not be needed. Ceramic capacitors are recommended for the flying capacitors C1 and C3 with values of 0.47µF to 2.2µF. Smaller values may be used in low output current applications (e.g., IOUT < 1mA). 6 U W U U Output Ripple Normal LTC1502-3.3 operation produces voltage ripple on the VOUT pin. Output voltage ripple is required for regulation. Low frequency ripple exists due to the hysteresis in the sense comparator and propagation delays in the charge pump enable/disable circuits. High frequency ripple is also present mainly from the ESR (equivalent series resistance) in the output capacitor. Typical output ripple (VIN = 1.25V) under maximum load is 50mV peak-to-peak with a low ESR 10µF output capacitor. The magnitude of the ripple voltage depends on several factors. High input voltages increase the output ripple since more charge is delivered to COUT per charging cycle. Large output current load and/or a small output capacitor ( 0.5Ω) on the output pin cause high frequency voltage spikes on VOUT with every clock cycle. There are several ways to reduce the output voltage ripple. A larger COUT capacitor (22µF or greater) will reduce both the low and high frequency ripple due to the lower COUT charging and discharging dV/dt and 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 chosen. A reasonable compromise is to use a 10µF to 22µF tantalum capacitor in parallel with a 1µF to 3.3µF ceramic capacitor on VOUT to reduce both the low and high frequency ripple. An RC filter may also be used to reduce high frequency voltage spikes (see Figure 2). 8 10µF 1502-3.3 F01 VOUT LTC1502-3.3 + VOUT 10µF TANTALUM 1µF CERAMIC VOUT LTC1502-3.3 8 2Ω + 10µF + VOUT 10µF 1502-3.3 F02 Figure 2. Output Ripple Reduction Techniques LTC1502-3.3 APPLICATIONS INFORMATION Short-Circuit Protection When the output is shorted to ground, the LTC1502-3.3 will continuously charge the C2 capacitor up to approximately 1.4 times VIN, and then discharge C2 into the shorted output. Since the discharging of C2 into VOUT will bring the C2 voltage below the COMP2 start-up comparator trip voltage, the output charge pump will be forced Hi-Z while C2 charges up again. Hence, the internal charge pump gate drive voltage is limited to (1.4)(VIN(MAX)) on the C2 pin, and no continuous current is supplied to VOUT. The resulting output short-circuit current is limited to under 20mA (typ) thereby allowing the LTC1502-3.3 to endure an indefinite output short circuit without damage. When the short is removed, the part will start up, and operate normally. PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. 0.040 ± 0.006 (1.02 ± 0.15) 0.007 (0.18) 0.021 ± 0.006 (0.53 ± 0.015) 0° – 6° TYP SEATING PLANE 0.012 (0.30) 0.0256 REF (0.65) BSC * DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE ** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE S8 Package 8-Lead Plastic Small Outline (Narrow 0.150) (LTC DWG # 05-08-1610) 0.189 – 0.197* (4.801 – 5.004) 0.010 – 0.020 × 45° (0.254 – 0.508) 0.008 – 0.010 (0.203 – 0.254) 0°– 8° TYP 0.053 – 0.069 (1.346 – 1.752) 8 0.004 – 0.010 (0.101 – 0.254) 0.228 – 0.244 (5.791 – 6.197) 0.150 – 0.157** (3.810 – 3.988) 7 6 5 0.014 – 0.019 (0.355 – 0.483) TYP *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE 0.016 – 0.050 (0.406 – 1.270) 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. U U W U U MS8 Package 8-Lead Plastic MSOP (LTC DWG # 05-08-1660) 0.118 ± 0.004* (3.00 ± 0.102) 0.034 ± 0.004 (0.86 ± 0.102) 8 76 5 0.006 ± 0.004 (0.15 ± 0.102) 0.193 ± 0.006 (4.90 ± 0.15) 0.118 ± 0.004** (3.00 ± 0.102) MSOP (MS8) 1098 1 23 4 0.050 (1.270) BSC SO8 1298 1 2 3 4 7 LTC1502-3.3 TYPICAL APPLICATIONS Single Cell to 3.3V DC/DC Converter with Shutdown 1 10µF 1µF 100Ω 2 C2 + SHDN µCONTROLLER Single Cell Battery Backup Supply with Autoswitchover and No Reverse Current MAIN SUPPLY 5V 3 1µF 2 1 10µF 1µF 7 8 10µF 1µF 100Ω LT1521-3.3 1 VOUT = 3.3V IOUT = 300mA (IOUT = 10mA IN BACKUP MODE) TRICKLE CHARGE 1.1M 3.9V VTRIP* 470k 3 4 5 6 *REFERRED TO MAIN SUPPLY RELATED PARTS PART NUMBER LT1307/LT1307B LT1308A/LT1308B LTC1517-3.3 LTC1558/LTC1559 LT1610 LT1611 LT1613 LT1615 LTC1682 DESCRIPTION 750mA Single Cell Micropower 600kHz PWM DC/DC Converter 2A Single Cell Micropower 600kHz PWM DC/DC Converter Micropower Regulated 3.3V Charge Pump DC/DC Converter Backup Battery Controller with Programmable Output Single Cell Micropower 1.7MHz PWM DC/DC Converter 1.4MHz Inverting Switching Regulator 1.4MHz Boost Switching Regulator Micropower Boost Switching Regulator Low Noise Doubler Charge Pump 8 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900 q FAX: (408) 434-0507 q www.linear-tech.com U VOUT C3 + 8 7 1µF 10µF VOUT = 3.3V IOUT = 10mA C1 LTC1502-3.3 3 6 C1–/SHDN C3 – 4 5 GND VIN 10µF SINGLE CELL NiCd OR ALKALINE 1502-3.3 TA03 150k C2 VOUT 1 CELL NiCd 2 C1+ C3 + LTC1502-3.3 6 3 C3 – C1–/SHDN 5 4 GND VIN 10µF 7 LTC1540 + – 8 Q1 2N7002 LOGIC LOW = BACKUP MODE 1502-3.3 TA04 2 1 COMMENTS 3.3V at 75mA from 1 Cell, MSOP Package 3.3V at 300mA from 1 Cell, SO-8 Package IOUT = 15mA (VIN ≥ 2.5V) Uses Single NiCd Cell, 100mW Output (Min) 30µA IQ, MSOP Package 5V to – 5V at 150mA, Low Output Noise, SOT-23 package 5V at 200mA from 3.3V Input, SOT-23 Package 30µA IQ, VOUT Up to 34V, SOT-23 Package 60µVRMS Noise, IOUT Up to 50mA, MSOP 15023f LT/TP 0899 4K • PRINTED IN USA © LINEAR TECHNOLOGY CORPORATION 1999