LTC1515 Series Step-Up/Step-Down Switched Capacitor DC/DC Converters with Reset U DESCRIPTION FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ The LTC®1515, LTC1515-3/5 and LTC1515-3.3/5 are micropower switched capacitor DC/DC converters that produce a regulated output voltage by either stepping up or stepping down the input voltage. Output voltage is adjustable using an external resistor divider (LTC1515) or programmable to either 3V/5V (LTC1515-3/5) or 3.3V/5V (LTC1515-3.3/5) using a logic pin. Adjustable/Selectable 3V, 3.3V or 5V Output Voltages 2V to 10V Input Voltage Range Up to 50mA Output Current Only Three External Capacitors Required Soft Start Limits Inrush Current at Turn-On Low Operating Current: 60µA Very Low Shutdown Current: < 1µA Shutdown Disconnects Load from VIN VOUT Programmable to 3V/5V or 3.3V/5V Short-Circuit and Overtemperature Protected 650kHz Switching Frequency Open-Drain Power-On Reset Output Daisy-Chained Control Outputs Available in SO-8 Package A unique architecture allows the parts to accommodate a wide input voltage range (2V to 10V) while maintaining ±4% regulation. Additional circuitry prevents excessive inrush current and output voltage ripple when large VIN to VOUT differentials are present. An internal power-on reset circuit forces the POR pin low on initial power-up. The POR output remains low until 200ms (typ) after VOUT is in regulation. U APPLICATIONS ■ ■ ■ ■ The parts are short-circuit and overtemperature protected. Battery life is maximized by very low operating currents (ICC = 60µA typ, ICC < 1µA in shutdown). All three parts are available in an SO-8 package. SIM Interface in GSM Cellular Telephones Smart Card Readers Local Power Supplies Portable Equipment , LTC and LT are registered trademarks of Linear Technology Corporation. U TYPICAL APPLICATION LTC1515-X 5V Output vs Input Voltage Programmable 3.3V/5V Power Supply with Power-On Reset 5.2 100k RESET 5V 3.3V 1 SHDN VOUT 8 VOUT = 3.3V OR 5V IOUT = 50mA 2 7 POR VIN LTC1515-3.3/5 3 6 5/3 C1+ 4 GND C1– 5 + + 10µF 0.22µF 10µF VIN 4-CELL NiCd OUTPUT VOLTAGE (V) ON OFF IOUT = 10mA 5/3 = 3V 5.1 5.0 4.9 LTC1515 • TA01 4.8 2 3 4 5 8 6 7 INPUT VOLTAGE (V) 9 10 LT1515 • TA02 1 LTC1515 Series W W U W ABSOLUTE MAXIMUM RATINGS (Note 1) VIN to GND ................................................ – 0.3V to 12V VOUT to GND ............................................. – 0.3V to 12V SHDN, 5/3, FB to GND .............................. – 0.3V to 12V VOUT Short-Circuit Duration ............................. Indefinite Operating Temperature Range Commercial ............................................. 0°C to 70°C Industrial ............................................ – 40°C to 85°C Storage Temperature Range ................ – 65°C to 150°C Lead Temperature (Soldering, 10 sec)................. 300°C U W U PACKAGE/ORDER I FOR ATIO ORDER PART NUMBER TOP VIEW SHDN 1 8 VOUT POR 2 7 VIN FB 3 6 C1 + GND 4 5 C1 – S8 PACKAGE 8-LEAD PLASTIC SO TOP VIEW SHDN 1 8 VOUT POR 2 7 VIN 5/3 3 6 C1 + GND 4 5 C1 – LTC1515CS8 LTC1515IS8 S8 PART MARKING 1515 1515I TJMAX = 125°C, θJA = 110°C/W ORDER PART NUMBER LTC1515CS8-3/5 LTC1515CS8-3.3/5 LTC1515IS8-3/5 LTC1515IS8-3.3/5 S8 PART MARKING S8 PACKAGE 8-LEAD PLASTIC SO 151535 515335 TJMAX = 125°C, θJA = 110°C/W 515I35 15I335 Consult factory for Military grade parts. ELECTRICAL CHARACTERISTICS VIN = 2V to 10V, SHDN = 3V, C1 = 0.22µF, CIN = COUT = 10µF unless otherwise noted (Note 2). PARAMETER CONDITIONS VIN Operating Voltage VOUT = 5V VOUT = 3V/3.3V VOUT = ADJ ● ● ● MIN 2.7 2.0 2.0 VOUT = 3V (LTC1515-3/5) 2V ≤ VIN ≤ 8V, IOUT ≤ 15mA 3V ≤ VIN ≤ 8V, IOUT ≤ 50mA ● ● 2.88 2.88 VOUT = 3.3V (LTC1515-3.3/5) 2V ≤ VIN ≤ 8V, IOUT ≤ 15mA 3V ≤ VIN ≤ 8V, IOUT ≤ 50mA ● ● VOUT = 5V (LTC1515-3/5, LTC1515-3.3/5) 2.7V ≤ VIN ≤ 10V, IOUT ≤ 15mA 3.3V ≤ VIN ≤ 10V, IOUT ≤ 50mA VFB Feedback Voltage LTC1515, VFB Ramping Negative TYP MAX UNITS 10 8 10 V V V 3.0 3.0 3.12 3.12 V V 3.17 3.17 3.3 3.3 3.43 3.43 V V ● ● 4.8 4.8 5.0 5.0 5.2 5.2 V V ● 1.190 1.232 1.275 V VFB Feedback Hysteresis LTC1515 Effective Output Resistance LTC1515, VIN = 3V, Step-Up Mode ● 1 VIN Operating Current VIN ≤ 5V, IOUT = 0, SHDN = 3V VIN > 5V, IOUT = 0, SHDN = 3V ● ● VIN Shutdown Current SHDN = 0V, VIN ≤ 5V SHDN = 0V, VIN > 5V ● Output Ripple Full Load (Note 2) 60 75 % 30 Ω 100 135 µA µA 1 25 µA µA 100 mVP-P Switching Frequency Full Load ● 500 650 800 kHz 5/3, SHDN Input Threshold VIL VIH ● ● 0.4 1.0 1.0 1.6 V V 5/3, SHDN = VIN 5/3, SHDN = 0V ● ● –1 –1 1 1 µA µA FB Input Current FB = 1.232V ● – 50 50 nA POR Output Low Voltage ISINK = 100µA, VIN = 3V ● 0.4 V 5/3, SHDN Input Current 2 0.05 LTC1515 Series ELECTRICAL CHARACTERISTICS VIN = 2V to 10V, SHDN = 3V, C1 = 0.22µF, CIN = COUT = 10µF unless otherwise noted (Note 2). PARAMETER CONDITIONS POR Leakage Current VPOR = 5V ● MIN –1 POR Trip Point (With Respect to VOUT) VOUT Ramping Negative ● – 10 TYP MAX UNITS µA 1 – 7.5 POR Trip Point Hysteresis –5 % 1 IOUT Short-Circuit Current VOUT = 0V tON Soft Start Turn-On Time POR Delay After VOUT Above POR Threshold 12 ● The ● denotes specifications which apply over the full operating temperature range. Note 1: Absolute Maximum Ratings are those values beyond which the life of the device may be impaired. % 40 mA 280 ms 4 140 ● ms 200 Note 2: For VIN ≥ 8V, COUT = 22µF. U W TYPICAL PERFORMANCE CHARACTERISTICS LTC1515-X 3.3V Efficiency vs Output Current 100 VOUT = 3.3V TA = 25°C VIN = 2.7V VIN = 2V 80 80 EFFICIENCY (%) VIN = 4.4V VIN = 2.7V 60 250 VIN = 6V OUTPUT VOLTAGE RIPPLE (mVP-P) 100 EFFICIENCY (%) LTC1515-X 3.3V Output Voltage Ripple vs Input Voltage LTC1515-X 5V Efficiency vs Output Current VIN = 6V 40 VIN = 3.3V 60 VIN = 8V 40 20 20 VOUT = 5V TA = 25°C 0 0.01 0.1 1 10 OUTPUT CURRENT (mA) 0 0.01 100 COUT = 22µF 100 COUT = 47µF 10 1515 G04 6 4 INPUT VOLTAGE (V) 8 10 1515 G03 VOUT = 5V IOUT = 0mA 3.35 3.30 100 80 25°C 60 85°C –40°C 40 20 3.20 8 2 120 3.25 0 COUT = 47µF 0 OPERATING CURRENT (µA) OUTPUT VOLTAGE (V) OUTPUT VOLTAGE RIPPLE (mVP-P) COUT = 10µF 6 4 INPUT VOLTAGE (V) 50 LTC1515-X Operating Current vs Input Voltage VOUT = 3.3V IOUT = 10mA COUT = 10µF TA = 25°C 3.40 150 COUT = 22µF 100 100 3.45 VOUT = 5V IOUT = 10mA TA = 25°C 2 COUT = 10µF LTC1515-X 3.3V Output Voltage vs Input Voltage 250 0 150 1515 G02 LTC1515-X 5V Output Voltage Ripple vs Input Voltage 50 200 0 0.1 1 10 OUTPUT CURRENT (mA) 1515 G01 200 VOUT = 3.3V IOUT = 10mA TA = 25°C 0 2 6 4 INPUT VOLTAGE (V) 8 10 1515 G05 0 2 6 4 INPUT VOLTAGE (V) 8 10 1515 G06 3 LTC1515 Series U W TYPICAL PERFORMANCE CHARACTERISTICS 100 VOUT = 5V IOUT = 10mA TA = 25°C VOUT = 3.3V IOUT = 10mA TA = 25°C 80 60 40 EFFICIENCY (%) 80 EFFICIENCY (%) EFFICIENCY (%) 100 100 VOUT = 3V IOUT = 10mA TA = 25°C 80 20 LTC1515-X 5V Efficiency vs Input Voltage LTC1515-X 3.3V Efficiency vs Input Voltage LTC1515-X 3V Efficiency vs Input Voltage 60 40 40 0 2 6 4 INPUT VOLTAGE (V) 8 10 20 60 0 2 6 4 INPUT VOLTAGE (V) 8 20 10 1515 G09 2 4 8 6 INPUT VOLTAGE (V) 10 1515 G08 1515 G07 LTC1515-X Shutdown Supply Current vs Input Voltage 12 LTC1515-X Step-Down Mode 5V Load Transient Response LTC1515-X Step-Up Mode 5V Load Transient Response 25 POSITIVE SUPPLY CURRENT (µA) SHDN = 0V VOUT AC COUPLED 100mV/DIV VOUT AC COUPLED 100mV/DIV 20 15 10 50mA IOUT 50mA/DIV 85°C 0mA IOUT 50mA/DIV 25°C 5 –40°C VIN = 8V, VOUT = 5V, COUT = 10µF, TA = 25°C 1515 G10 VIN = 3.3V, VOUT = 5V, COUT = 10µF, TA = 25°C 1515 G11 0 0 2 6 4 INPUT VOLTAGE (V) 8 10 1515 G12 U U U PIN FUNCTIONS SHDN (Pin 1): Shutdown Input. A logic low on the SHDN pin puts the part into shutdown mode. A logic high (VSHDN ≥ 1.6V) enables the part. At high VIN voltages, the SHDN pin may still be controlled with 3V logic without causing a large rise in VIN quiescent current. The SHDN pin may not float; connect to VIN if unused. POR (Pin 2): Open-Drain Power-On Reset Output. This pin will pull low upon initial power-up, during shutdown or until VOUT has been within 6.5% of its regulated value for more than 200ms typ. 5/3 (LTC1515-X) (Pin 3): Output Voltage Select. A logic high on the 5/3 pin will force VOUT to regulate to 5V. A logic 4 low will force VOUT to 3V (LTC1515-3/5) or 3.3V (LTC15153.3/5). As with the SHDN pin, the 5/3 pin may be driven with 3V logic over the entire VIN range. The 5/3 pin may not float. FB (LTC1515) (Pin 3): Feedback Input. The voltage on this pin is compared to the internal reference voltage (1.232V) to keep the output in regulation. An external resistor divider is required between VOUT and FB to adjust the output voltage. Total divider resistance should not exceed 2M. GND (Pin 4): Ground. Should be tied to a ground plane for best performance. C1– (Pin 5): Charge Pump Flying Capacitor, Negative Terminal. LTC1515 Series U U U PIN FUNCTIONS C1+ (Pin 6): Charge Pump Flying Capacitor, Positive Terminal. VIN (Pin 7): Charge Pump Input Voltage. May be between 2V and 10V. VIN should be bypassed with a ≥ 10µF low ESR capacitor as close as possible to the pin for best performance. VOUT (Pin 8): Regulated Output Voltage. Pin selectable to either 3V/5V, 3.3V/5V or adjustable using an external resistor divider (LTC1515). VOUT should be bypassed with a ≥ 10µF low ESR capacitor as close as possible to the pin for best performance. W W SI PLIFIED BLOCK DIGRAM C1– VIN C1+ STEP-UP/STEP-DOWN CHARGE PUMP VOUT (LTC1515-X) SHDN (LTC1515-X) – 650kHz OSCILLATOR EN + POR FB (LTC1515) – EN RESET COUNTER VOS + 5/3 (LTC1515-X) 1.232V VREF GND LTC1515 • BD U W U U APPLICATIONS INFORMATION Regulator Operation The regulator section of the LTC1515, LTC1515-3/5 and LTC1515-3.3/5 consists of a charge pump, reference, comparator and some logic. The divided down output voltage is compared to the internal reference voltage. When the divided output drops below the reference voltage, the charge pump is enabled, which boosts the output back into regulation. Hysteresis in the comparator forces the regulator to burst on and off and causes approximately 100mV of peak-to-peak ripple to appear at the output. By enabling the charge pump only when needed, the parts achieve high efficiencies with low output load currents. Each part’s charge pump has a unique architecture that allows the input voltage to be either stepped up or stepped down to produce a regulated output. Internal circuitry senses the VIN to VOUT differential voltage and controls the charge pump operating mode. In addition, the effective output impedance of the charge pump is internally adjusted to prevent large inrush currents and allow for a wide input voltage range. When the input voltage is lower than the output voltage, the charge pump operates as a step-up voltage doubler. When the input voltage is greater than the output, the charge pump operates as a step-down gated switch. 5 LTC1515 Series U U W U APPLICATIONS INFORMATION Output Voltage Selection ROUT The output voltage of the LTC1515 is selected using an external resistor divider (see Figure 1). The output voltage is determined using the following formula: VOUT = (1.232V)[1 + (R1/R2)] The total resistance of R1 and R2 should not exceed 2M, otherwise excess ripple may appear at VOUT. 1 R1 2 3 SHDN VOUT POR VIN LTC1515 8 + 2VIN FB C1+ 6 GND C1– 5 VOUT IOUT COUT – LT1515 • F02 Figure 2. Step-Up Mode Equivalent Circuit 40 30 IOUT = 20mA IOUT = 50mA 20 10 0 1 7 2 3 4 5 INPUT VOLTAGE (V) LT1515 • F03 Figure 3. Step-Up Mode ROUT vs Input Voltage R2 4 LTC1515 • F01 Figure 1. LTC1515 Output Voltage Selection Maximum VOUT and IOUT Calculations for the LTC1515 The maximum output voltage and current available with the LTC1515 can be calculated based on the effective output resistance of the charge pump and the open circuit output voltage. In step-up mode, the open circuit output voltage is approximately 2VIN (see Figure 2). In step-down mode, the open circuit output voltage equals VIN. The relationship between ROUT and VIN in step-up mode is shown in Figure 3. The following formulas can be used to find the maximum output voltage that may be programmed using the LTC1515 for a given minimum input voltage and output current load. Step-Up Mode: Max VOUT = (2)(Min VIN) – (IOUT)(ROUT) Step-Down Mode: Max VOUT = (Min VIN) – (IOUT)(ROUT) When VIN – (IOUT)(ROUT) is less than the programmed VOUT, the part will automatically switch from step-down mode to step-up mode. In both step-up mode and step- 6 + – OUTPUT RESISTANCE (Ω) The LTC1515-X versions have internal resistor networks which set the output voltage. The 5/3 pin controls an internal switch that shorts out a portion of the resistor network to change the output voltage. A logic high on this pin produces a 5V output and a low produces either a 3V output or a 3.3V output. down mode, ROUT is internally adjusted to ensure that the maximum output current rating can be met. Capacitor Selection For best performance, low ESR capacitors are recommended for both CIN and COUT to reduce noise and ripple. The CIN 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. Increasing the size of COUT to 22µF or greater will reduce output voltage ripple — particularly with high VIN voltages (8V or greater). A ceramic capacitor is recommended for the flying capacitor C1 with a value of 0.1µF or 0.22µF. Smaller values may be used in low output current applications. Output Ripple Normal LTC1515 series operation produces voltage ripple on the VOUT pin. Output voltage ripple is required for the parts to regulate. 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 LTC1515 Series U U W U APPLICATIONS INFORMATION (equivalent series resistance) in the output capacitor. Typical output ripple (VIN < 8V) under maximum load is 100mV peak-to-peak with a low ESR, 10µF output capacitor. For applications requiring VIN to exceed 8V, a 22µF or larger COUT capacitor is recommended to maintain maximum ripple in the 100mV range. 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. A large C1 flying capacitor (> 0.22µF) also increases ripple in step-up mode for the same reason. Large output current load and/or a small output capacitor (<10µF) results in higher ripple due to higher output voltage dV/dt. High ESR capacitors (ESR > 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 large 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 (<0.5Ω) 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 or LC filter may also be used to reduce high frequency voltage spikes (see Figure 4). LTC1515/ LTC1515-X VOUT 8 + VOUT 1µF CERAMIC 15µF TANTALUM LTC1515/ LTC1515-X VOUT + 10µF TANTALUM Internal soft start circuitry controls the rate at which VOUT may be charged from 0V to its final regulated value. The typical start-up time from VOUT = 0V to 5V is 4ms. This corresponds to an effective VOUT charging current of only 12.5mA for a 10µF output capacitor (27.5mA for 22µF, etc.). Note that any output current load present during start-up will add directly to the charging currents mentioned above. The soft start circuitry limits start-up current both at initial power-up and when coming out of shutdown. As the VIN (or boosted VIN) to VOUT voltage differential grows, the effective output impedance of the charge pump is automatically increased by internal voltage sensing circuitry. This feature minimizes the current spikes pulled from VIN whenever the charge pump is enabled and helps to reduce both input and output ripple. Power-On Reset The POR pin is an open-drain output that pulls low when the output voltage is out of regulation. When the VOUT rises to within 6.5% of regulation, an internal timer is started which releases POR after 200ms (typ). In shutdown, the POR output is pulled low. In normal operation, an external pull-up resistor is generally used between the POR pin and VOUT. Protection Features 2Ω 8 ing out of shutdown mode. Whenever large VIN (or boosted VIN) to VOUT voltage differentials are present, most charge pumps will pull large current spikes from the input supply. Only the effective charge pump output impedance limits the current while the charge pump is enabled. This may disrupt input supply regulation, especially if the input supply is a low power DC/DC converter or linear regulator. The LTC1515 family minimizes inrush currents both at start-up and under high VIN to VOUT operation. + VOUT 10µF TANTALUM LT1515 • F04 Figure 4. Output Ripple Reduction Techniques Inrush Currents A common problem with switched capacitor regulators is inrush current—particularly during power-up and com- All of the parts contain thermal shutdown and shortcircuit protection features. The parts will shut down when the junction temperature reaches approximately 150°C and will resume operation once the junction temperature has dropped back to approximately 140°C. The parts will limit output current to 12mA (typ) when a short circuit condition (VOUT < 100mV) exists. The parts can survive an indefinite short to GND. 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 LTC1515 Series U TYPICAL APPLICATIONS Low Power, Low Noise Step-Up/Step-Down 5V Supply with Reset 1.4M 470k ON OFF 1 2 RESET 3 4 402k VOUT SHDN POR LTC1515 FB GND VIN 5.5V 8 7 C1+ 6 C1– 5 + VIN = 3V TO 10V + 2Ω 22µF 10µF 0.22µF + 8 IN LT1121-5 1 OUT GND Programmable 3V/5V GSM SIM Card Power Supply 10µF + 10µF 3 1 ON OFF NC 5V 3V SHDN VOUT 8 VOUT = 5V IOUT = 20mA VRIPPLE < 1mVP-P LTC1515 • TA03 VOUT = 3V OR 5V IOUT = 15mA 2 7 POR VIN LTC1515-3/5 6 5/3 C1+ 4 5 C1– GND + 3 + 10µF Li-Ion 10µF 0.1µF LTC1515 • TA04 Positive and Negative Supply 1 ON OFF NC VIN SHDN VOUT 2 VOUT = 5V IOUT = 15mA, 2.7V ≤ VIN ≤ 4.4V IOUT = 50mA, 3.3V ≤ VIN ≤ 4.4V 8 7 POR VIN LTC1515-3/5 6 5/3 C1+ 4 5 GND C1– + 3 0.22µF + 10µF 10µF 470Ω 8.2k Q2 Q1 * CENTRAL SEMICONDUCTOR CMPSH-35 DUAL SCHOTTKY ** OPTIONAL CIRCUITRY FOR MAINTAINING –VOUT WITH LOW VOUT LOADS Q1, Q2: 2N3904 U PACKAGE DESCRIPTION 2.4k 0.22µF ** * + 0.053 – 0.069 (1.346 – 1.752) 0°– 8° TYP 0.016 – 0.050 0.406 – 1.270 LTC1515 • TA05 Dimensions in inches (millimeters) unless otherwise noted. 0.189 – 0.197* (4.801 – 5.004) (LTC DWG # 05-08-1610) 0.008 – 0.010 (0.203 – 0.254) VOUT = –1V TO –3.5V IOUT = 5mA 10µF S8 Package 8-Lead Plastic Small Outline (Narrow 0.150) 0.010 – 0.020 × 45° (0.254 – 0.508) VIN = 2.7V TO 4.4V 0.014 – 0.019 (0.355 – 0.483) *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 8 7 6 5 0.004 – 0.010 (0.101 – 0.254) 0.050 (1.270) TYP 0.150 – 0.157** (3.810 – 3.988) 0.228 – 0.244 (5.791 – 6.197) 1 2 3 4 SO8 0996 RELATED PARTS PART NUMBER LTC1514 Series LTC1516 LTC1517-5 LTC1522 LTC1555/LTC1556 LTC660 8 DESCRIPTION Step-Up/Step-Down Switched Capacitor DC/DC Converters Micropower, Regulated 5V Charge Pump DC/DC Converter Micropower, Regulated 5V Charge Pump DC/DC Converter Micropower, Regulated 5V Charge Pump DC/DC Converter SIM Power Supply and Level Translators 100mA CMOS Voltage Converter Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417● (408)432-1900 FAX: (408) 434-0507● TELEX: 499-3977 ● www.linear-tech.com COMMENTS VIN 2V to 10V, 3.3V and 5V Versions, IOUT to 50mA IOUT = 20mA (VIN ≥ 2V), IOUT = 50mA (VIN ≥ 3V) LTC1522 Without Shutdown and Packaged in SOT-23 Available in 8-Pin MSOP, 6µA Quiescent Current, IOUT = 20mA Step-Up/Step-Down SIM Power Supply and Level Translators 5V to – 5V Conversion with Low Voltage Loss 1515f LT/TP 0298 4K • PRINTED IN USA LINEAR TECHNOLOGY CORPORATION 1997