MIC2660 Micrel MIC2660 IttyBitty™ Charge Pump Preliminary Information General Description Features The MIC2660 IttyBitty™ charge pump functions as a lowcurrent, step-up converter where conventional inductor based, dc-to-dc converters are too complex and expensive. This device features a complete, self-contained charge pump in a tiny 5-lead SOT-23-5 package. The MIC2660 is powered from a 3V to 5V nominal supply and produces nominally 5V to 9V as a function of the input voltage. The output is unregulated and follows a load-line type function. • 3V input produces approx. 5V unregulated output* 3.8mA with 1µF external output capacitor 2.5mA without external capacitor • 5V input produces approx. 9V unregulated output* 4.5mA output without external capacitor • CMOS-logic compatible enable • ESD protected The MIC2660 can be used with or without external components. When used with two noncritical external capacitors, a 3V input will produce 5V at 3.8mA. With no external components, a 3V input will produce 5V at 2.5mA. The MIC2660 charge pump consists of an approximately 18MHz oscillator and a voltage tripler. The MIC2660 is available in the SOT-23-5 package and is rated for –40°C to +85°C ambient temperature range. Applications • • • • • • • • Squib firing Refresh Burst/dump Low duty cycle load LCD bias generator Local 5V logic supply MOSFET driver Battery or solarcell boost Ordering Information Part Number Temperature Range Package MIC2660BM5 –40°C to +85°C SOT-23-5 Typical Application +3V Input 0.01µF MIC2660 1 5 3 IN OUT EN GND 2 Enable Disable +5V, 2.5mA* Output 0.01µF * The output is unregulated and follows a load-line type function Low-Current Unregulated Step-Up Supply Timing Diagram 2V EN 0V 5V 0.2 µs 1.3 µs OUT 1V 0V Output vs. Enable Input 1997 10-11 10 MIC2660 Micrel Pin Configuration OUT GND IN 3 2 1 Part Identification C10 4 5 NC EN SOT-23-5 (M5) Pin Description Pin Number Pin Name Pin Function 1 IN 2 GND Ground: Power return. 3 OUT Output: Charge pump output. Connect to load. 4 NC Not internally connected. 5 EN Enable (Input): CMOS compatible input. EN high (VEN = VIN) enables the charge pump . EN low (VIN = 0V) disables the charge pump. Supply (Input): +3V to +5V supply. Absolute Maximum Ratings Input Voltage (VIN) ..................................................... +5.5V Enable Voltage (VEN) ......................................... VIN + 1.3V Ambient Temperature Range (TA) ............. –40°C to +85°C Lead Temperature, Soldering 10sec. ........................ 300°C Package Thermal Resistance SOT-23-5 θJA .................................................... 220°C/W SOT-23-5 θJC .................................................... 130°C/W Electrical Characteristics Parameter Condition (Note 1) Min Typ Output Voltage, Enabled VIN = 3V, VEN = VIN, COUT = 1000pF, RL = 2kΩ 4.5 5 V VIN = 5V, VEN = VIN, COUT = 1000pF, RL = 2kΩ 8.1 9 V VIN = 3V, VEN = GND, COUT = 1000pF, RL = 2kΩ .9 1.0 1.3 V VIN = 5V, VEN = GND, COUT = 1000pF, RL = 2kΩ 2.9 3.0 3.3 V VIN = 3V, VEN = VIN, RL = 2kΩ 14.5 19.5 mA VIN = 5V, VEN = VIN, RL = 2kΩ 28.5 38.5 mA Output Voltage, Disabled Input Current Quiescent Current Output Current Enable Threshold Max Units VIN = 3V, VEN < 0.4V 1.5 3 µA VIN = 5V, VEN < 0.4V 3.5 5 µA VIN = 3V, VEN = VIN, VOUT = VOUT min 1.9 2.5 mA VIN = 5V, VEN = VIN, VOUT = VOUT min 3.4 4.5 mA VIN = 3V 1.5 V VIN = 5V 2.5 V 10 µA Enable Current VIN = 5V, VEN = VIN Turn-On Time VIN = 3V Load = 2kΩ, COUT = 1000pF, Note 2 200 ns Turn-Off Time VIN = 3V Load = 2kΩ, COUT = 1000pF, Note 3 1.3 µs General Note: Devices are ESD protected, however handling precautions are recommended. Note 1: Typicals values at TA = 25°C. Minimum and maximum values at –40°C ≤ TA ≤ +85°C. Note 2: Turn-on time is the time between VEN = 0.5 × VIN and VOUT = 0.9 (VOUTmax – VOUTmin) for a rising EN input. Note 3: Turn-off time is the time between VEN = 0.5 × VIN and VOUT = VIN – 1.9V for a falling EN input. 10-12 1997 MIC2660 Micrel Typical Characteristics Output Voltage vs. Supply Voltage Output Voltage vs. Supply Voltage 20 15 NO LOAD 10 3mA 2mA 5 1mA 0 2.0 2.5 3.0 3.5 4.0 4.5 SUPPLY VOLTAGE (V) 20 COUT = NONE TA = 25° C 15 NO LOAD 10 3mA 2mA 5 1mA 0 2.0 5.0 Output Voltage vs. Supply Voltage 2.5 3.0 3.5 4.0 4.5 SUPPLY VOLTAGE (V) 10 3mA 2mA 1mA 0 2.0 2.5 3.0 3.5 4.0 4.5 SUPPLY VOLTAGE (V) 10 3mA 5 2mA 1mA 15 NO LOAD 10 3mA 5 2mA 1mA Efficiency vs. Output Voltage 2.5 3.0 3.5 4.0 4.5 SUPPLY VOLTAGE (V) COUT = 1µF TA = 125° C 15 NO LOAD 10 3mA 5 2mA 1mA 0 2.0 5.0 Efficiency vs. Output Voltage 35 35 30 30 2.5 3.0 3.5 4.0 4.5 SUPPLY VOLTAGE (V) 35 30 2mA 15 10 0 25 20 2mA 15 1mA 10 COUT = NONE TA = 25° C 5 3mA 2 4 6 8 10 12 OUTPUT VOLTAGE (V) 0 14 0 Efficiency vs. Output Voltage 25 2mA 15 COUT = 1µF TA = -55° C 1997 0 1mA 2 4 6 8 10 12 OUTPUT VOLTAGE (V) EFFICIENCY (%) EFFICIENCY (%) 3mA 5 15 1mA 10 0 14 COUT = NONE TA = 125° C 0 35 3mA 30 25 2mA 20 15 1mA 10 0 14 Efficiency vs. Output Voltage COUT = 1µF 5 T = 25° C A 14 2 4 6 8 10 12 OUTPUT VOLTAGE (V) 40 35 30 0 2 4 6 8 10 12 OUTPUT VOLTAGE (V) 40 10 2mA 20 Efficiency vs. Output Voltage 35 20 25 5 0 2 4 6 8 10 12 OUTPUT VOLTAGE (V) 10-13 EFFICIENCY (%) 0 1mA COUT = NONE TA = -55° C 5 EFFICIENCY (%) EFFICIENCY (%) EFFICIENCY (%) 3mA 20 5.0 Efficiency vs. Output Voltage 3mA 25 5.0 20 COUT = 1µF TA = 25° C 0 2.0 5.0 2.5 3.0 3.5 4.0 4.5 SUPPLY VOLTAGE (V) Output Voltage vs. Supply Voltage OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V) NO LOAD 5 NO LOAD 0 2.0 5.0 20 COUT = 1µF TA = -55° C 15 COUT = NONE TA = 125° C 15 Output Voltage vs. Supply Voltage 20 OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V) COUT = NONE TA = -55° C OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V) 20 Output Voltage vs. Supply Voltage 3mA 30 25 2mA 20 15 1mA 10 COUT = NONE TA = 125° C 5 14 0 0 2 4 6 8 10 12 OUTPUT VOLTAGE (V) 14 10 MIC2660 Micrel Block Diagram IN MIC2660 D1 2× 3× D2 Q1 EN OSC XLO Q2 OUT D3 Q3 C1 XLO Q4 C2 GND Functional Description Refer to the block diagram. The MIC2660 charge pump consists of an oscillator and a voltage tripler. A logic-high applied to EN activates the charge pump. The charge pump produces an output voltage that is higher than the input voltage. Supply Input IN (supply input) is rated for +2.7V to +5.5V. Ouput OUT is connected to IN, less 3 diode drops, at all times. Enable EN (enable) is a CMOS input. A logic low turns the oscillator off. The threshold is approximately half the supply voltage. A floating EN input may cause unpredictable operation. Oscillator The oscillator produces a square wave at approximately 18MHz. It has a noninverting and an inverting output. Crossover Lockout The charge pump contains two crossover lockout (XLO) circuits. Each crossover lockout circuit drives a totem pole, consisting of a P-channel MOSFET and an N-channel MOSFET. The crossover lockout alternately switches the MOSFETs with no significant transition current (shoot-through current from supply to ground). Tripler Voltage stepup is performed by charging an internal capacitor then switching the charged capacitor in series with the supply voltage to produce a higher voltage. A description of the nominal voltage tripler output is: VOUT = 3VIN – 3VD. where: VOUT = output voltage VIN = supply voltage VD = voltage drop across forward biased diode All formulas are simplified. Refer to the last paragraph of this subsection about the actual output voltage. The following sequence describes the basic operation of the tripler by showing how the voltage at the “2×” and “3×” nodes, V2× and V3×, increases. Q2 turns on, completing the ground path to charge C1 (and the 2× node) to the supply voltage, less a diode voltage drop. V2× (charging) = VIN – VD1 After Q2 turns off, Q1 turns on. The Q1-Q2 side of C1 is switched (offset upward) from ground to VIN. The 2× node, that was nominally at the supply voltage, becomes nominally twice the supply voltage. V2× = VIN – VD1 + VIN While Q1 is on, Q4 is also on. When Q4 is on, the nominally doubled voltage at the 2× node is applied across C2, through D2. V3× (charging) = VIN – VD1 + VIN – VD2 After Q4 turns off, Q3 turns on. The Q3-Q4 side of C2 is switched from ground to VIN. The 3× node, that was nominally twice the supply voltage, becomes nominally three times the supply voltage. V3× = VIN – VD1 + VIN – VD2 + VIN The tripled voltage is available at the output through D3. VOUT = VIN – VD1 + VIN – VD2 + VIN – VD3 The output is nominally 3 times the supply voltage less the voltage drop across three diodes. The actual output is lower. These simplified formulas do not show that the voltage across the capacitors decreases when charge flows to the following stage or output. An actual device also has some internal loss. ESD Protection Zener diodes are provided at IN, EN, and OUT to limit ESD voltage. 10-14 1997 MIC2660 Micrel Charge-Pump/Dump A large capacitor can be charged to the unloaded tripled voltage output after a time based on the maximum current provided by the MIC2660. A 1000µF Capacitor can be charged from 2V to approximately 12V in less than 3 seconds by a 5V powered MIC2660. (i = C dv/dt). Applications Information Electromagnetic Interference The 18MHz oscillator may cause interference to radio circuits. 0.01µF bypass capacitors should be mounted close to the IN and OUT terminals. Low-Side MOSFET Charge-Pump Driver A standard MOSFET requires approximately 15V to fully enhance the gate for minimum RDS(on). Substituting a logiclevel MOSFET reduces the required gate voltage, allowing an MIC2660 to be used as an low-side FET driver. A 3V powered MIC2660 will fully enhance a logic-level N-channel MOSFET low-side switch, with a 5k gate pulldown resistor, in less than 1ms after the enable pin rises above 1.5V. The 1nF MOSFET gate capacitance will be discharged to turn-off in less than 10ms after the enable pin goes below 1.5V. Once charged, a maximum current of 3mA may be drawn continuously at the 12V level. A high value bleeder resistor (100k) is not needed to prevent spikes from exceeding the capacitor voltage rating, since the MIC2660’s internal 15V ESD zener limits maximum output. A 68Ω resistor in series with the output limits short-circuit current to 30mA. +5V MIC2660 1 100k 5 Load Supply +3V to +5V 100k 5 Enable Disable IN EN OUT EN GND 3 68Ω 2 +12V 1000µF 0.1µF RLOAD MIC2660 1 IN OUT GND 3 Figure 2. Charge-Pump/Dump 2 5-Volt Lamp Flasher 1µF 0.1µF An IttyBitty MIC1557 oscillator provides a short pulse once per second, enabling the CS pin of an MIC2660, which charges the gate-to-drain capacitance of a logic-level N-channel MOSFET to approximately 9V, which turns on a lamp. When the CS pin is low, a 2k resistor discharges the gate capacitance, turning off the lamp. A resistor (RS) in series with a diode determines the “on” time to approximately RS||RT×CT,while RT and CT set the “off” time to 1.1RT×CT. Figure 1. Charge-Pump Driver An MIC2660 boosts a 5V input to 9V–12V to fully enhance an N-channel MOSFET, which may have its drain connected to a higher voltage, through a high-side load. A TTL high signal applied to CS enables the internal oscillator, which quickly develops 9V–12V at the gate of the MOSFET, clamped by a zener diode. A resistor from the gate to ground ensures that the FET will turn off quickly when the MIC2660 is turned off. +5V RS 470k RT1MΩ MIC1557 CT 0.68µF 4 VS 1 T/T 2 GND CS OUT 5 MIC2660 1 IN OUT 3 5 EN GND 2 Figure 3. 5-Volt Lamp Flasher 1997 10 5V lamp 3 10-15 IRL3103 N-channel FET 2k 0.1µF