MAX1730EUB

19-1618; Rev 0; 4/00 50mA Regulated Step-Down Charge Pump for 1.8V or 1.9V Logic Features The MAX1730 regulated step-down charge pump generates up to 50mA at fixed output voltages of 1.8V or 1.9V from an input voltage in the 2.7V to 5.5V range. Specifically designed to provide high-efficiency logic supplies in applications that demand a compact design, the MAX1730 employs fractional conversion techniques to provide efficiency exceeding that of a linear regulator. ♦ > 85% Peak Efficiency The MAX1730 operates at up to 2MHz, permitting the use of small 0.22µF flying capacitors while maintaining low 75µA quiescent supply current. Proprietary softstart circuitry prevents excessive current from being drawn from the supply during startup, making the MAX1730 compatible with higher impedance sources such as alkaline and lithium-ion cells. ♦ No Inductor Required ♦ 50mA Guaranteed Output Current ♦ Dual-Mode 1.8V or 1.9V Output ♦ ±3% Output Voltage Accuracy ♦ Up to 2MHz Operating Frequency ♦ Small 0.22µF Capacitors ♦ 2.7V to 5.5V Input Voltage Range ♦ Output Disconnects from Input in Shutdown Mode ♦ Small 10-Pin µMAX Package (1.09mm max height) The MAX1730 is available in a space-saving 10-pin µMAX package that is only 1.09mm high and occupies one-half the area of an 8-pin SO. Applications Low-Voltage Logic Supplies Ordering Information PART Wireless Handsets MAX1730EUB TEMP. RANGE PIN-PACKAGE -40°C to +85°C 10 µMAX PDAs PC Cards Hand-Held Instruments Pin Configuration Typical Operating Circuit TOP VIEW INPUT 2.7V TO 5.5V 1µF FB 1 SHDN IN OUTPUT 1.8V OR 1.9V, UP TO 50mA OUT 4.7µF MAX1730 C1P 10 IN SHDN 2 C1P 3 C1N 4 7 C2N GND 5 6 PGND MAX1730 9 OUT 8 C2P µMAX C2P 0.22µF 0.22µF C1N FB C2N GND PGND ________________________________________________________________ Maxim Integrated Products 1 For free samples and the latest literature, visit www.maxim-ic.com or phone 1-800-998-8800. For small orders, phone 1-800-835-8769. MAX1730 General Description MAX1730 50mA Regulated Step-Down Charge Pump for 1.8V or 1.9V Logic ABSOLUTE MAXIMUM RATINGS IN, OUT, SHDN, FB to GND .....................................-0.3V to +6V C1P, C1N, C2P, C2N to GND ......................-0.3V to (VIN + 0.3V) GND to PGND.....................................................................±0.3V Output Short-Circuit Duration ........................................Indefinite Continuous Power Dissipation (TA = +70°C) 10-Pin µMAX (derate 5.6mW/°C above +70°C) ...........444mW Junction Temperature ......................................................+150°C Operating Temperature Range ...........................-40°C to +85°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature Range (soldering, 10s)......................+300°C Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (VIN = +3.6V, FB = GND, SHDN = IN, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER Input Voltage Range SYMBOL Input Undervoltage Lockout Output Voltage CONDITIONS VIN Falling edge (100mV hysteresis) VOUT VIN = 2.7V to 5.5V, IOUT = 0 to 50mA MIN MAX UNITS 2.7 TYP 5.5 V 2.3 2.6 V FB = GND 1.746 1.80 1.854 FB = IN 1.843 1.90 1.957 V Output Leakage Current OUT forced to 1.8V, VIN = 1.8V to 5.5V, SHDN = GND 1 5 µA No-Load Supply Current SHDN = IN 75 150 µA Shutdown Supply Current VIN = 4.2V, SHDN = GND, VOUT = 1.8V or GND 1 5 µA Output Short-Circuit Current VOUT = GND 45 125 mA 2.0 2.5 MHz 1.5 Oscillator Frequency Thermal Shutdown Threshold 150 °C Thermal Shutdown Threshold Hysteresis 15 °C VIN Transition Voltage (VIN Rising) FB = GND From 1:1 to 2:3 3.1 3.2 3.35 From 2:3 to 1:2 4.00 4.12 4.30 4.1 Startup Timer SHDN Logic Input High Voltage VIH VIN = 2.7V to 5.5V SHDN Logic Input Low Voltage VIL VIN = 2.7V to 5.5V Shutdown Logic Input Current ISHDN SHDN = IN or GND 2 ms 1.4 -1 _______________________________________________________________________________________ V V 0.6 V 1 µA 50mA Regulated Step-Down Charge Pump for 1.8V or 1.9V Logic MAX1730 ELECTRICAL CHARACTERISTICS (VIN = +3.6V, FB = GND, SHDN = IN, TA = -40°C to +85°C, unless otherwise noted.) (Note 1) PARAMETER Input Voltage Range SYMBOL MIN MAX UNITS 2.7 5.5 V 2.3 2.6 V FB = GND 1.746 1.854 FB = IN 1.843 1.957 VIN Input Undervoltage Lockout Output Voltage CONDITIONS Falling edge (100mV hysteresis) VOUT VIN = 2.7V to 5.5V, IOUT = 0 to 50mA Output Leakage Current OUT forced to 1.8V, VIN = 1.8V to 5.5V, SHDN = GND No-Load Supply Current SHDN = IN Shutdown Supply Current VIN = 4.2V, SHDN = GND Output Short-Circuit Current VOUT = GND Oscillator Frequency FB = GND SHDN Logic Input High Voltage VIH VIN = 2.7V to 5.5V SHDN Logic Input Low Voltage VIL VIN = 2.7V to 5.5V Shutdown Logic Input Current ISHDN SHDN = IN or GND 5 µA 150 µA 5 µA 125 mA MHz 1.5 2.5 From 1:1 to 2:3 3.1 3.35 From 2:3 to 1:2 4.00 4.30 f VIN Transition Voltage (VIN Rising) 1.4 -1 V V V 0.6 V 1 µA Note 1: Specifications to -40°C are guaranteed by design, not production tested. _______________________________________________________________________________________ 3 Typical Operating Characteristics (VIN = +3.6V, FB = GND, SHDN = IN, CIN = 1µF, C1 = C2 = 0.22µF, COUT = 4.7µF, TA = +25°C, unless otherwise noted.) EFFICIENCY vs. INPUT VOLTAGE 60 VIN = 2.7V 50 90 EFFICIENCY (%) 70 VIN = 5.0V 40 85 80 75 70 85 80 75 70 65 65 60 60 10 55 55 0 50 10 100 1000 50 2.5 3.0 3.5 4.0 4.5 OUTPUT CURRENT (mA) INPUT VOLTAGE (V) INPUT CURRENT vs. INPUT VOLTAGE OUTPUT VOLTAGE vs. OUTPUT CURRENT 50 40 30 20 VIN = 5.0V 1.83 OUTPUT VOLTAGE (V) NO-LOAD SUPPLY CURRENT 5.5 VIN = 2.7V 1.79 1.75 3.0 3.5 4.0 4.5 INPUT VOLTAGE (V) 5.0 5.5 4.5 5.0 5.5 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.2 0 2.5 4.0 0.4 SHUTDOWN CURRENT 2.0 3.5 OUTPUT VOLTAGE vs. INPUT VOLTAGE 1.77 10 3.0 INPUT VOLTAGE (V) VIN = 3.3V 1.81 2.5 OUTPUT VOLTAGE (V) 60 1.85 5.0 MAX1730 TOC05 1 70 4 90 20 0.1 IOUT = 50mA 95 30 MAX1730 TOC04 EFFICIENCY (%) 80 IOUT = 25mA 95 MAX1730 TOC06 VIN = 3.3V EFFICIENCY (%) VIN = 3.6V 100 MAX1730 TOC02 90 EFFICIENCY vs. INPUT VOLTAGE 100 MAX1730 TOC01 100 MAX1730 TOC02 EFFICIENCY vs. OUTPUT CURRENT INPUT CURRENT (µA) MAX1730 50mA Regulated Step-Down Charge Pump for 1.8V or 1.9V Logic IOUT = 0 to 50mA 0 0.1 1 10 100 OUTPUT CURRENT (mA) 1000 0 1 2 3 4 INPUT VOLTAGE (V) _______________________________________________________________________________________ 5 6 50mA Regulated Step-Down Charge Pump for 1.8V or 1.9V Logic LINE-TRANSIENT RESPONSE STARTUP AND SHUTDOWN RESPONSE LOAD-TRANSIENT RESPONSE MAX1730 TOC07 MAX1730 TOC09 MAX1730 TOC08 4V RL = 72Ω 50mA IOUT 5mA VIN VO 1V/div 3V IIN 50mA/div VOUT AC-COUPLED 20mV/div VOUT AC-COUPLED 50mV/div VSHDN 5V/div 10µs/div 100µs/div 10µs/div Pin Description PIN NAME FUNCTION 1 FB Feedback Input. Connect FB to GND for a 1.8V output. Connect FB to IN for a 1.9V output. Do not leave FB unconnected. 2 SHDN Active-Low Shutdown Input. Connect to logic control or to IN for normal operation. OUT disconnects from the input in shutdown and goes to high impedance. 3 C1P C1 Flying Capacitor Positive Connection 4 C1N C1 Flying Capacitor Negative Connection 5 GND Ground 6 PGND 7 C2N C2 Flying Capacitor Negative Connection 8 C2P C2 Flying Capacitor Positive Connection 9 OUT Output. Bypass to GND with a 4.7µF or greater capacitor. 10 IN Power Ground Input Supply. Connect to a +2.7V to +5.5V supply. Bypass to GND with a 1µF ceramic capacitor as close to the IC as possible. _______________________________________________________________________________________ 5 MAX1730 Typical Operating Characteristics (continued) (VIN = +3.6V, FB = GND, SHDN = IN, CIN = 1µF, C1 = C2 = 0.22µF, COUT = 4.7µF, TA = +25°C, unless otherwise noted.) 50mA Regulated Step-Down Charge Pump for 1.8V or 1.9V Logic MAX1730 Functional Diagram OUT FB FB CONTROL C1P DRIVERS C1N VREF + OSCILLATOR MAX1730 SWITCH ARRAY C2P CONTROL LOGIC C2N SHUTDOWN PGND SHDN GND Detailed Description The MAX1730 step-down charge pump automatically switches between charge pump configurations (Figures 1, 2, and 3) and utilizes pulse-skipping pulse-frequency modulation (PFM) to provide a regulated output voltage with high efficiency. The output voltage is pin-selectable to 1.8V or 1.9V. The MAX1730 accepts inputs between 2.7V and 5.5V and guarantees up to 50mA output current. Charge-Pump Configurations Charge pumps work by passing energy through capacitors. They generally work in two phases. In the first phase, the input source charges the flying capacitors. The input capacitor helps reduce the source’s input impedance. In the second phase, the switching capacitors transfer their charge to the output as needed. Figure 1 shows the 1:1 charge-pump configuration. C1 and C2 charge in parallel between IN and GND during the first phase. In the second phase, C1 and C2 connect in parallel between OUT and GND. 6 IN Figure 2 shows the 3:2 charge-pump configuration. C1 and C2 charge in parallel between IN and OUT during the first phase. In the second phase, C1 and C2 connect in series between OUT and GND. Figure 3 shows the 2:1 charge-pump configuration. C1 and C2 charge in parallel between IN and OUT during the first phase. In the second phase, C1 and C2 connect in parallel between OUT and GND. Pulse-Skipping PFM and Mode Transitions In the MAX1730, pulse-skipping PFM mode pauses the oscillator when the output is in regulation. Using the 2:1 charge-pump configuration as an example, when the output is set to half the input, the switching frequency is near the oscillator frequency. However, for outputs below half the input, switching pauses once the desired output level is achieved. With no output current, the device switches occasionally. With higher levels of current, the switching frequency increases to supply the load. _______________________________________________________________________________________ 50mA Regulated Step-Down Charge Pump for 1.8V or 1.9V Logic MAX1730 VIN VOUT = VIN CIN COUT C1 C2 NOTE: SWITCH STATES SET FOR STAGE 1. ALL SWITCHES REVERSE STATE FOR STAGE 2. Figure 1. 1:1 Capacitor Configuration VIN VIN CIN CIN C1 C2 C2 C1 VOUT = 2 VIN 3 COUT NOTE: SWITCH STATES SET FOR STAGE 1. ALL SWITCHES REVERSE STATE FOR STAGE 2. Figure 2. 3:2 Capacitor Configuration To maximize efficiency, the MAX1730 automatically switches between charge-pump configurations (Figures 1, 2, and 3). Efficiency is greatest when the IN/OUT voltage ratio is close to the voltage ratio of the selected capacitor configuration and decreases for output voltages lower than the divider ratio. To choose between configurations, the MAX1730 senses the input voltage and the output voltage. The MAX1730 uses a control scheme with hysteresis to prevent oscillation between capacitor configurations. COUT VOUT = 1 VIN 2 NOTE: SWITCH STATES SET FOR STAGE 1. ALL SWITCHES REVERSE STATE FOR STAGE 2. Figure 3. 2:1 Capacitor Configuration Applications Information Setting the Output Voltage For an output voltage of 1.8V, connect FB to GND. For an output voltage of 1.9V, connect FB to IN. _______________________________________________________________________________________ 7 Shutdown Layout Considerations The MAX1730 features an active-low shutdown pin (SHDN) to decrease supply current to below 5µA. When in shutdown, the output disconnects from the input and OUT goes to high impedance. The MAX1730’s high-frequency operation demands careful layout. All components should be placed as close to the IC as possible, with priority going to CIN, C1, and C2. Traces should be kept short, wide, and as straight as possible. Connect PGND and GND together with a low-impedance ground plane. Capacitor Selection The input capacitor provides the charge pump with a lowimpedance supply. For most applications, a 1µF ceramic capacitor is adequate. Lower-value capacitors and those with higher ESR may be inadequate for proper operation and may result in lower output current capability and higher output ripple. Chip Information TRANSISTOR COUNT: 2295 To reduce the output voltage ripple, the value of the output capacitor should exceed that of the flying capacitors (C1 + C2) by 10:1 or more. Values for C1 and C2 between 0.22µF and 0.47µF are recommended for most applications. Use ceramic capacitors to increase maximum output current and improve efficiency. Package Information 10LUMAX.EPS MAX1730 50mA Regulated Step-Down Charge Pump for 1.8V or 1.9V Logic Note: The MAX1730 does not have an exposed pad. Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.