LTC1516IS8#TRPBF

LTC1516 Micropower, Regulated 5V Charge Pump DC/DC Converter U DESCRIPTION FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Ultralow Power: Typical Operating ICC = 12µA Short Circuit/Thermal Protection Regulated 5V ±4% Output 2V to 5V Input Range No Inductors ICC in Shutdown: < 1µA Output Current: 20mA (VIN > 2V) 50mA (VIN > 3V) Shutdown Disconnects Load from VIN Internal Oscillator: 600kHz Compact Application Circuit (0.1 in2) 8-Pin SO Package U APPLICATIONS ■ ■ ■ ■ 2-Cell to 5V Conversion Li-Ion Battery Backup Supplies Local 3V to 5V Conversion 5V Flash Memory Programmer Smart Card Readers The LTC1516 operates as either a doubler or a tripler depending on VIN and output load conditions to improve overall efficiency. The part has thermal shutdown and can survive a continuous short from VOUT to GND. In shutdown the load is disconnected from VIN. The LTC1516 is available in an 8-pin SO package in both commercial and industrial temperature grades. , LTC and LT are registered trademarks of Linear Technology Corporation. U ■ The LTC®1516 is a micropower charge pump DC/DC converter that produces a regulated 5V output from a 2V to 5V supply. Extremely low supply current (12µA typical with no load, < 1µA in shutdown) and low external parts count (two 0.22µF flying capacitors and two 10µF capacitors at VIN and VOUT) make the LTC1516 ideally suited for small, light load battery-powered applications. Typical efficiency (VIN = 3V) exceeds 70% with load currents between 50µA and 50mA. Modulating the SHDN pin keeps the typical efficiency above 70% with load currents all the way down to 10µA. TYPICAL APPLICATION Efficiency vs Output Current 0.22µF 90 VIN = 3V 1 8 C1– C1+ 2 + 10µF 3 + 10µF 4 VIN SHDN LTC1516 VOUT GND C2+ C2 – 7 ON/OFF 6 5 EFFICIENCY (%) 80 VIN = 2V TO 5V 70 LOW IQ MODE (SEE FIGURE 3) SHDN = 0V 60 0.22µF VOUT = 5V ±4% IOUT = 0mA TO 20mA, VIN ≥ 2V IOUT = 0mA TO 50mA, VIN ≥ 3V 50 0.01 0.1 1 10 OUTPUT CURRENT (mA) 100 1516 • F01 1516 • TA01 Figure 1. Regulated 5V Output from a 2V to 5V Input 1 LTC1516 W U U U W W W ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION (Note 1) VIN to GND ...................................................– 0.3V to 6V VOUT to GND ................................................– 0.3V to 6V SHDN to GND ..............................................– 0.3V to 6V 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 ORDER PART NUMBER TOP VIEW C1+ 1 8 C1– VIN 2 7 SHDN VOUT 3 6 GND C2+ 4 5 C2– LTC1516CS8 LTC1516IS8 S8 PART MARKING S8 PACKAGE 8-LEAD PLASTIC SO 1516 1516I TJMAX = 125°C, θJA = 150°C/ W Consult factory for Military grade parts. ELECTRICAL CHARACTERISTICS VIN = 2V to 5V, C1 = C2 = 0.22µF, CIN = COUT = 10µF, TMIN to TMAX unless otherwise specified (Note 3). SYMBOL PARAMETER VIN Input Voltage VOUT Output Voltage ICC fOSC VIH VIL IIH IIL tON Supply Current Output Ripple Efficiency Switching Frequency SHDN Input Threshold CONDITIONS ● 2V ≤ VIN ≤ 5V, IOUT ≤ 20mA 3V ≤ VIN ≤ 3.6V, IOUT ≤ 50mA 3.6V ≤ VIN ≤ 5V, IOUT ≤ 50mA, TA = 25°C (Note 2) 2V ≤ VIN ≤ 5V, IOUT = 0mA, SHDN = 0V 2V ≤ VIN ≤ 5V, IOUT = 0mA, SHDN = VIN Full Load VIN = 3V, IOUT = 20mA Full Load TYP 12 0.005 100 82 600 ● ● ● VOUT Turn-On Time VSHDN = VIN VSHDN = 0V VIN = 3V, IOUT = 0mA (Note 3) ● ● MAX 5 5.2 5.2 5.2 20 1 (0.7)(VIN) 0.4 1 1 ● SHDN Input Current 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 2 ● ● MIN 2 4.8 4.8 4.8 –1 –1 500 UNITS V V V V µA µA mV % kHz V V µA µA µs Note 2: At input voltages > 3.6V and ambient temperatures >70°C, continuous power dissipation must be derated to maintain junction temperatures below 125°C. Derate 6mW/°C above 70°C in SO-8. Note 3: The LTC1516 is tested with the capacitors shown in Figure 1. LTC1516 U W TYPICAL PERFORMANCE CHARACTERISTICS 120 MAXIMUM OUTPUT CURRENT (mA) EFFICIENCY (%) 80 70 60 20 COUT = 10µF TA = 25°C IOUT = 10mA 100 C1 = C2 = 0.22µF SUPPLY CURRENT (µA) 90 C1 = C2 = 0.1µF 80 60 C1 = C2 = 0.047µF 40 C1 = C2 = 0.022µF 20 C1 = C2 = 0.01µF 50 2.5 3.0 3.5 4.0 INPUT VOLTAGE (V) 4.5 5.0 2 3 4 INPUT VOLTAGE (V) 1516 • G01 15 10 5 0 2.0 2 5 3 4 INPUT VOLTAGE (V) Output Voltage vs Input Voltage 5 1516 • G03 1516 • G02 Output Voltage vs Output Current Load Transient Response, VIN = 3V 5.10 5.10 VIN = 3V IOUT = 20mA 5.05 OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V) No Load Supply Current vs Input Voltage Output Current vs Input Voltage Efficiency vs Input Voltage 5.00 4.95 IOUT , 0mA TO 25mA, 10mA/DIV 5.05 5.00 VOUT, AC COUPLED, 100mV/DIV 4.95 1516 • G04 4.90 4.90 1 2 3 4 INPUT VOLTAGE (V) 5 6 0.01 0.1 1 10 OUTPUT CURRENT (mA) 1516 • G04 100 1516 • G05 U U U PIN FUNCTIONS C1+ (Pin 1): Flying Capacitor 1, Positive Terminal. GND (Pin 6): Ground. VIN (Pin 2): Input Supply Voltage. SHDN (Pin 7): Active High CMOS Logic-Level Shutdown Input. VOUT (Pin 3): 5V Output Voltage (VOUT = 0V in Shutdown). C2+ (Pin 4): Flying Capacitor 2, Positive Terminal. C1 – (Pin 8): Flying Capacitor 1, Negative Terminal. C2 – (Pin 5): Flying Capacitor 2, Negative Terminal. 3 LTC1516 W BLOCK DIAGRAM VIN 10µF SHDN + S2A VOUT + S1A C2 + 10µF 0.22µF S2B COMP1 C2 – S1B CLOCK 1 COMP2 CONTROL LOGIC S1C C1 + 0.22µF CLOCK 2 S2C C1 – COMP3 VOS S1D S3 VREF CHARGE PUMP CHARGE PUMP SHOWN IN TRIPLER MODE, DISCHARGE CYCLE LTC1516 • BD U W U U APPLICATIONS INFORMATION Operation The LTC1516 uses a switched capacitor charge pump to boost VIN from 2V to 5V to a regulated 5V ±4% output voltage. Regulation is achieved by sensing the output voltage through an internal resistor divider and enabling the charge pump when the output voltage droops below the lower trip point of COMP2. When the charge pump is enabled, a 2-phase, nonoverlapping clock controls the charge pump switches. Clock 1 closes the S1 switches which enable the flying capacitors, C1 and C2, to charge up to the VIN voltage. Clock 2 closes the S2 switches which stack C1 and C2 in series with VIN and connect the top plate of C2 to the output capacitor at VOUT. This sequence of charging and discharging continues at a free-running frequency of 600kHz (typ) until the output has risen to the upper trip point of COMP2 and the charge pump is disabled. When the charge pump is disabled, the LTC1516 draws only 8µA (typ) from VIN which provides high efficiency at low load conditions. To achieve the highest efficiency over the entire VIN range, the LTC1516 operates as either a doubler or a tripler 4 depending on VIN and output load conditions. COMP1 and COMP2 determine whether the charge pump is in doubler mode or tripler mode. COMP1 forces the part into tripler mode if VIN is < 2.55V, regardless of output load. When VIN is > 2.55V, the part will be in doubler mode using only C2 as a flying capacitor. In doubler mode, if the output droops by 50mV under heavy loads, COMP3 will force the charge pump into tripler mode until VOUT climbs above the upper trip point of COMP3. Under these VIN and load conditions, the nominal VOUT will be approximately 50mV lower than the no load nominal VOUT. This method of sensing VIN and output load results in efficiency greater than 80% with VIN between 2.5V and 3V. In shutdown mode, all circuitry is turned off and the part draws only leakage current (< 1µA) from the VIN supply. VOUT is also disconnected from VIN. The SHDN pin is a CMOS input with a threshold of approximately VIN/2; however, the SHDN pin can be driven by logic levels that exceed the VIN voltage. The part enters shutdown mode when a logic high is applied to the SHDN pin. The SHDN pin cannot float; it must be driven with a logic high or low. LTC1516 U W U U APPLICATIONS INFORMATION Short-Circuit/Thermal Protection During short-circuit conditions, the LTC1516 will draw between 200mA and 400mA from VIN causing a rise in the junction temperature. On-chip thermal shutdown circuitry disables the charge pump once the junction temperature exceeds 135°C, and reenables the charge pump once the junction temperature falls back to 115°C. The LTC1516 will cycle in and out of thermal shutdown indefinitely without latchup or damage until the VOUT short is removed. Capacitor Selection For best performance, it is recommended that low ESR capacitors be used 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, CIN may not be needed. Increasing the size of COUT to 22µF or greater will reduce output voltage ripple. Ceramic or tantalum capacitors are recommended for the flying caps C1 and C2 with values in the range of 0.1µF to 1µF. Note that large value flying caps (> 0.22µF) will increase output ripple unless COUT is also increased. For very low load applications, C1 and C2 may be reduced to 0.01µF to 0.047µF. This will reduce output ripple at the expense of efficiency and maximum output current. 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 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). In low load or high VIN applications, smaller values for C1 and C2 may be used to reduce output ripple. The smaller C1 and C2 flying capacitors (0.022µF to 0.1µF) deliver less charge per clock cycle to the output capacitor resulting in lower output ripple. However, the smaller value flying caps also reduce the maximum IOUT capability as well as efficiency. LTC1516 3 VOUT + Output Ripple Normal LTC1516 operation produces voltage ripple on the VOUT pin. Output voltage ripple is required for the LTC1516 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 due to ESR (Equivalent Series Resistance) in the output capacitor. Typical output ripple under maximum load is 100mVP-P with a low ESR 10µF output capacitor. The magnitude of the ripple voltage depends on several factors. High input voltages (VIN > 3.3V) increase the output ripple since more charge is delivered to COUT per clock cycle. Large C1 and C2 flying capacitors (> 0.22µF) also increase ripple for the same reason. Large output current load and/or a small output capacitor (< 10µF) results in LTC1516 3 VOUT 15µF TANTALUM 1µF CERAMIC 2Ω + VOUT 5V + 10µF VOUT 5V 10µF 1516 F02 Figure 2. Output Ripple Reduction Techniques Inrush Currents During normal operation, VIN will experience current transients in the 100mA to 200mA range whenever the charge pump is enabled. During start-up, these inrush currents may approach 500mA. For this reason, it is important to minimize the source resistance between the input supply and the VIN pin to prevent start-up problems and large input voltage transients. 5 LTC1516 U U W U APPLICATIONS INFORMATION Ultralow Quiescent Current (IQ < 5µA) Regulated Supply The LTC1516 contains an internal resistor divider (refer to Block Diagram) which draws only 1.5µA (typ) from VOUT. During no-load conditions, the internal load causes a droop rate of only 150mV per second on VOUT with COUT = 10µF. Applying a 5Hz to 100Hz, 95% to 98% duty cycle signal to the SHDN pin ensures that the circuit of Figure 3 comes out of shutdown frequently enough to maintain regulation during no-load or low-load conditions. Since the part spends nearly all of its time in shutdown, the no-load quiescent current (see Figure 4a) is approximately equal to (VOUT)(1.5µA)/(VIN)(Efficiency). The LTC1516 must be out of shutdown for a minimum duration of 200µs to allow enough time to sense the output and keep it in regulation. As the VOUT load current increases, the frequency with which the part is taken out of shutdown must also be increased to prevent VOUT from drooping below 4.8V during the OFF phase (see Figure 4b). A 100Hz 98% duty cycle signal on the SHDN pin ensures proper regulation with load currents as high as 100µA. When load current greater than 100µA is needed, the SHDN pin must be forced low as in normal operation. The typical no-load supply current for this circuit with VIN = 3V is only 3.2µA. 0.22µF 1 VIN = 2V TO 5V 2 + 10µF 3 + 10µF 4 C1+ C1– VIN SHDN LTC1516 VOUT GND C2+ C2 – 8 7 FROM MPU SHDN PIN WAVEFORMS: 6 5 LOW IQ MODE (5Hz TO 100Hz, 95% TO 98% DUTY CYCLE) VOUT LOAD ENABLE MODE IOUT ≤ 100µA (IOUT = 100µA TO 50mA) 0.22µF 1516 • F03 VOUT = 5V ±4% Figure 3. Ultralow Quiescent Current (