19-1600; Rev 1; 6/00 Buck/Boost Regulating Charge Pump in MAX Features Regulated Output Voltage (Fixed 3.3V or Adjustable 2.5V to 5.5V) 100mA Guaranteed Output Current +1.6V to +5.5V Input Voltage Range Low 50A Quiescent Supply Current 1A Shutdown Mode Load Disconnected from Input in Shutdown High 1.5MHz Operating Frequency Uses Small Ceramic Capacitors Short-Circuit Protection and Thermal Shutdown Small 10-Pin MAX Package Ordering Information Applications Li+ Battery-Powered Applications PART TEMP. RANGE PIN-PACKAGE MAX1759EUB -40C to +85C 10 MAX Miniature Equipment Backup Battery Boost Converters Translators Typical Operating Circuit CX IN +1.6V TO +5.5V CXN TOP VIEW CXP OUT IN OUT 3.3V AT 100mA POK 1 COUT CIN MAX1759 ON OFF POK SHDN FB Pin Configuration POWER OK SHDN 10 FB 2 MAX1759 9 OUT IN 3 8 CXP IN 4 7 CXN GND 5 6 PGND GND PGND MAX Dual Mode is a trademark of Maxim Integrated Products. ________________________________________________________________ Maxim Integrated Products 1 For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com. MAX1759 General Description The MAX1759 is a buck/boost regulating charge pump that generates a regulated output voltage from a single lithium-ion (Li+) cell, or two or three NiMH or alkaline cells for small hand-held portable equipment. The MAX1759 operates over a wide +1.6V to +5.5V input voltage range and generates a fixed 3.3V or adjustable (2.5V to 5.5V) output (Dual ModeTM). Maxim's unique charge-pump architecture allows the input voltage to be higher or lower than the regulated output voltage. Despite its high 1.5MHz operating frequency, the MAX1759 maintains low 50A quiescent supply current. Designed to be an extremely compact buck/boost converter, this device requires only three small ceramic capacitors to build a complete DC-DC converter capable of generating a guaranteed 100mA (min) output current from a +2.5V input. For added flexibility, the MAX1759 also includes an open-drain power-OK (POK) output that signals when the output voltage is in regulation. The MAX1759 is available in a space-saving 10-pin MAX package that is 1.09mm high and half the size of an 8-pin SO. MAX1759 Buck/Boost Regulating Charge Pump in MAX ABSOLUTE MAXIMUM RATINGS IN, OUT, FB, POK, SHDN to GND............................-0.3V to +6V PGND to GND.....................................................................0.3V CXN to GND ................................................-0.3V to (VIN + 0.3V) CXP to GND................-0.3V to (the greater of VIN or VOUT) + 1V OUT Short to GND .........................................................Indefinite Continuous Power Dissipation (TA = +70C) 10-Pin MAX (derate 5.6mW/C above +70C) .........444mW Operating Temperature Range .......................... -40C to +85C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) ................................ +300C 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 (Circuit of Figure 1, VIN = V SHDN = 2V, FB = PGND = GND, CIN = 10F, CX = 0.33F, COUT = 10F, TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Input Voltage Range Input Undervoltage Lockout Voltage VIN 1.6 VUVLO 0.6 Output Voltage Adjustment Range Output Voltage Maximum Output Current VOUT Quiescent Supply Current IQ Shutdown Supply Current IQ,SHDN Leakage Current into OUT in Shutdown SHDN Logic Input Voltage SHDN Input Leakage Current FB Regulation Voltage POK Trip Voltage POK Output Low Voltage VOL POK Leakage Current Switching Frequency V 3.3 3.43 3.17 3.3 3.43 100 mA ILOAD 100mA (RMS) 200 VIN = V SHDN = 4V, VFB = 0, stepping down 50 90 VIN = V SHDN = 2V, VFB = 0, stepping up 85 180 1.6V VIN 5.5V, V SHDN = 0 1 5 A VIN = 2V, VOUT = 3.3V, V SHDN = 0 1 5 A V SHDN = 5.5V mA 0.25 * VIN 0.7 * VIN -1 V A 1.235 1.265 V 25 200 nA Internal feedback 100 50 mV VIN = 1.65V, VOUT = 3.3V 1.205 1 A VFB = 1.27V External feedback 200 100 Falling edge at FB 1.0 1.1 1.2 V 5 100 mV 0.01 0.2 A 1.5 1.8 MHz ISINK = 0.5mA, VIN = 2V VPOK = 5.5V, VFB = 1.27V fOSC V 3.17 1.6V VIN 5.5V FB Dual-Mode Threshold 5.5 2V VIN 5.5V, 1mA ILOAD 50mA 1.6V VIN 5.5V VFB V 2.5V VIN 5.5V, 1mA ILOAD 100mA VIL FB Input Current 1.4 2.5 VIH I SHDN V 1.6V VIN 5.5V ILOAD,MAX 2.5V VIN 5.5V Transient Load Current 1.0 5.5 1.6V VIN 5.5V, VFB = 1V 1.2 mV Output Short-Circuit Current VOUT = 0, 2.5V VIN 5.5V, foldback current limit 110 mA Thermal Shutdown Temperature Rising temperature 160 C 20 C 90 % Thermal Shutdown Hysteresis Efficiency 2 VIN = 3.6V, ILOAD = 10mA _______________________________________________________________________________________ Buck/Boost Regulating Charge Pump in MAX (Circuit of Figure 1, VIN = V SHDN = 2V, FB = PGND = GND, CIN = 10F, CX = 0.33F, COUT = 10F, TA = -40C to +85C, unless otherwise noted.) (Note 1) PARAMETER MIN MAX UNITS VIN 1.6 5.5 V Input Undervoltage Lockout Voltage VUVLO 0.6 1.4 V Output Voltage VOUT 2V VIN 5.5V, 0 ILOAD 50mA 3.15 3.45 V 2.5V VIN 5.5V, 0 ILOAD 100mA 3.15 3.45 V 1.6V VIN 5.5V 2.5 5.5 V ILOAD,MAX 2.5V VIN 5.5V 100 Input Voltage Range SYMBOL Output Voltage Adjustment Range Maximum Output Current Quiescent Supply Current IQ Shutdown Supply Current IQ,SHDN Leakage Current into OUT in Shutdown SHDN Input Logic Voltage SHDN Input Leakage Current FB Regulation Voltage VIN = V SHDN = 2.5V, VFB = 0 180 1.6V VIN 5.5V, V SHDN = 0 6 A VIN = 2V, VOUT = 3.3V, V SHDN = 0 5 A 1.6V VIN 5.5V 1.6V VIN 5.5V VFB FB Dual Mode Threshold POK Trip Voltage VOL POK Leakage Current Switching Frequency 90 VIL I SHDN fOSC mA VIN = V SHDN = 4V, VFB = 0 VIH FB Input Bias Current POK Output Low Voltage CONDITIONS V SHDN = 5.5V VIN = 1.65V, VOUT = 3.3V 0.2 * VIN 0.7 * VIN A V V -1 1 A 1.205 1.265 V VFB = 1.27V 200 nA Internal feedback 40 mV External feedback 200 Falling edge at FB 1.0 mV 1.2 V ISINK = 0.5mA, VIN = 2V 100 mV VPOK = 5.5V 0.2 A 1.9 MHz 1.6V VIN 5.5V, VFB = 1V 1.1 Note 1: Specifications to -40C are guaranteed by design and are not production tested. _______________________________________________________________________________________ 3 MAX1759 ELECTRICAL CHARACTERISTICS Typical Operating Characteristics (Circuit of Figure 1, CIN = 10F, CX = 0.33F, COUT = 10F, VOUT = 3.3V, VIN = 2.5V, TA = +25C, unless otherwise noted.) IOUT = 50mA 40 MAX1759 toc02 3.30 80 IOUT = 50mA 70 60 50 IOUT = 100mA 40 30 3.25 20 IOUT = 10mA 10 3.20 0.001 0 2.5 IOUT = 10mA 90 3.35 20 3.5 4.5 5.5 0 0.01 0.1 1 10 100 1.5 1000 2.5 3.5 INPUT VOLTAGE (V) QUIESCENT CURRENT vs. INPUT VOLTAGE STARTUP INPUT VOLTAGE (VOUT < VIN) TYPICAL SWITCHING WAVEFORMS (VOUT < VIN) MAX1759 toc04 4 OUTPUT VOLTAGE (V) 1000 RLOAD = 33 100 RLOAD = 33 VIN = 4.2V 3 1 2 2 5.5 MAX1759 toc06 LOAD CURRENT (mA) 10,000 1 10 3 NO LOAD 1.5 2.5 3.5 4.5 5.5 0 0.5 1.5 2.5 3.5 4.5 INPUT VOLTAGE (V) TYPICAL SWITCHING WAVEFORMS (VOUT > VIN) LOAD-TRANSIENT RESPONSE (VOUT < VIN) RLOAD = 33 VIN = 2.5V 1 5s/div 5.5 CH1: VOUT, 20mV/div, AC-COUPLED CH2: VCXP, 5V/div CH3: VIN, 50mV/div, AC-COUPLED LOAD-TRANSIENT RESPONSE (VOUT > VIN) MAX1759 toc08 INPUT VOLTAGE (V) MAX1759 toc07 0.5 MAX1759 toc09 1 1 1 2 2 2 3 LOAD STEP: 10mA TO 100mA VIN = 4.2V 5s/div CH1: VOUT, 20mV/div, AC-COUPLED CH2: VCXP, 5V/div CH3: VIN, 50mV/div, AC-COUPLED 4 4.5 INPUT VOLTAGE (V) MAX1759 toc05 1.5 100 EFFICIENCY (%) 60 OUTPUT VOLTAGE (V) IOUT = 100mA 80 EFFICIENCY vs. INPUT VOLTAGE OUTPUT VOLTAGE vs. LOAD CURRENT 3.40 MAX1759 toc01 OUTPUT VOLTAGE RIPPLE (mV) 100 MAX1759 toc03 OUTPUT VOLTAGE RIPPLE vs. INPUT VOLTAGE QUIESCENT CURRENT (A) MAX1759 Buck/Boost Regulating Charge Pump in MAX 100s/div CH1: VOUT, 20mV/div, AC-COUPLED CH2: IOUT, 100mA/div LOAD STEP: 10mA TO 100mA VIN = 2.5V 100s/div CH1: VOUT, 20mV/div, AC-COUPLED CH2: IOUT, 100mA/div _______________________________________________________________________________________ Buck/Boost Regulating Charge Pump in MAX TURN-ON/OFF RESPONSE (VIN = 4.2V) 1 -4.2V RLOAD = 33 VIN = 4.2V RLOAD = 33 VIN = 2.5V 1 1 2 2 3 3 MAX1759 toc12 RLOAD = 33 TURN-ON/OFF RESPONSE (VIN = 2.5V) MAX1759 toc11 MAX1759 toc10 LINE-TRANSIENT RESPONSE 2 -2.5V 4 4 500s/div 100s/div CH1: VOUT, 20mV/div, AC-COUPLED CH2: VIN, 1V/div, AC-COUPLED 500s/div CH1: VOUT,1V/div CH2: IIN, 200mA/div CH3: VPOK, 5V/div CH4: VSHDN, 5V/div CH1: VOUT,1V/div CH2: IIN, 200mA/div CH3: VPOK, 5V/div CH4: VSHDN, 5V/div Pin Description PIN NAME FUNCTION 1 POK Open-Drain Power-OK Output. POK is high impedance when output voltage is in regulation. POK sinks current when VFB falls below 1.1V. Connect a 10k to 1M pull-up resistor from POK to VOUT for a logic signal. Ground POK or leave unconnected if not used. POK is high impedance in shutdown. 2 SHDN 3, 4 IN 5 GND 6 PGND 7 CXN Negative Terminal of the Charge-Pump Transfer Capacitor 8 CXP Positive Terminal of the Charge-Pump Transfer Capacitor 9 OUT Power Output. Bypass to GND with an output filter capacitor. 10 FB Shutdown Input. Drive high for normal operation; drive low for shutdown mode. OUT is high impedance in shutdown. Input Supply. Connect both pins together and bypass to GND with a ceramic capacitor (see Capacitor Selection section). Ground. Connect GND to PGND with a short trace. Power Ground. Charge-pump current flows through this pin. Dual-Mode Feedback. Connect FB to GND for 3.3V output. Connect to an external resistor divider to adjust the output voltage from 2.5V to 5.5V. _______________________________________________________________________________________ 5 MAX1759 Typical Operating Characteristics (continued) (Circuit of Figure 1, CIN = 10F, CX = 0.33F, COUT = 10F, VOUT = 3.3V, VIN = 2.5V, TA = +25C, unless otherwise noted.) MAX1759 Buck/Boost Regulating Charge Pump in MAX Detailed Description 0.33F The MAX1759's unique charge-pump architecture allows the input voltage to be higher or lower than the regulated output voltage. Internal circuitry senses VIN and V OUT and determines whether V IN must be stepped up or stepped down to produce the regulated output. When VIN is lower than VOUT, the charge pump operates as a regulated step-up voltage doubler. When VIN is higher than VOUT, the charge pump operates as a step-down gated switch. In voltage step-down mode (i.e., the input voltage is greater than the output voltage) with a light load, the controller connects CXN to PGND, and shuttles charge to the output by alternately connecting CXP from IN to OUT (see Figures 1 and 2). Although VIN is greater than VOUT, this scheme may not allow the MAX1759 to regulate the output under heavy loads. In this case, the MAX1759 will automatically switch to step-up mode. In step-up mode, the output is kept in regulation by modulating the charge delivered by the transfer capacitor (CX) to the load (see Figure 2). When lightly loaded, the charge pump switches only as necessary to supply the load, resulting in low quiescent current. Output voltage ripple does not increase with light loads. The MAX1759 features thermal shutdown with temperature hysteresis. When the die temperature exceeds 160C, the device shuts down. When the die cools by 20C, the MAX1759 turns on again. If high die temperature is caused by output overload and the load is not removed, the device will turn off and on, resulting in a pulsed output. Shutdown Mode Design Procedure Driving SHDN low places the MAX1759 in shutdown mode. This disables the charge-pump switches, oscillator, and control logic, reducing quiescent current to 1A. The output is high impedance in shutdown and is disconnected from the input. The POK output is high impedance in shutdown. Undervoltage Lockout The MAX1759 undervoltage lockout feature deactivates the device when the input voltage falls below 1V. Power-OK Output POK is an open-drain output that sinks current when the regulator feedback voltage falls below 1.1V. The feedback voltage can be either the internal resistordivider feedback voltage when in fixed output mode (FB tied to GND) or an external feedback voltage from an external resistive divider in adjustable output mode. A 10k to 1M pull-up resistor from POK to OUT may be used to provide a logic output. Connect POK to GND or leave unconnected if not used. Soft-Start and Short-Circuit Protection The MAX1759 features foldback short-circuit protection. This circuitry provides soft-start by limiting inrush current during startup and limits the output current to 110mA (typ) if the output is short-circuited to ground. 6 IN +1.6V TO +5.5V CXN CXP OUT IN OUT 3.3V AT 100mA 10F 10F 100k MAX1759 ON OFF POK SHDN FB POWER OK GND PGND Figure 1. Typical Application Circuit Thermal Shutdown Setting the Output Voltage The MAX1759 dual-mode feedback controller selects between the internally set 3.3V regulated output or an external resistive divider that allows adjustment of the output voltage from 2.5V to 5.5V. Connect FB to GND for a regulated 3.3V output. For an adjustable output, connect a resistive divider between OUT and GND. To ensure feedback-loop stability and to minimize error due to FB pin bias currents, the resistive divider current should be approximately 15A. In the following equation, choose R2 in the 50k to 100k range, and calculate R1 from the following formula (Figure 3): R1 = R2 [(VOUT / VFB) - 1] and VOUT = VFB (R1 + R2) / R2 where VOUT is the desired output voltage from 2.5V to 5.5V, and VFB is the internal regulation voltage, nominally 1.235V. The circuit of Figure 3 generates a regulated 2.5V, using external standard 1% resistor values. Surface-mount resistors should be placed close to the MAX1759, less than 5mm away from FB (see the PC Board Layout section). _______________________________________________________________________________________ Buck/Boost Regulating Charge Pump in MAX CXP 8 S1 S2 MAX1759 CXN 7 IN 3, 4 PGND 6 OUT 9 R1 MAX1759 BUCK-BOOST CONTROL SHDN BIAS 2 1.5MHz OSC R2 ENABLE FB 10 1.235V POK 1 OUT-LOW N 1.1V GND 0.1V 5 Figure 2. Functional Diagram _______________________________________________________________________________________ 7 MAX1759 Buck/Boost Regulating Charge Pump in MAX Capacitor Selection Optimize the charge-pump circuit for physical size, output current, and output ripple by selecting capacitors CIN, CX, and COUT. See Table 1 for suggested capacitor values. Note that capacitors must have low ESR (20m) to maintain low output ripple. Ceramic capacitors are recommended. In cost-sensitive applications where high output current is needed, the output capacitor may be a combination of a 1F ceramic in parallel with a 10F tantalum capacitor. The ceramic capacitor's low ESR will help keep output ripple within acceptable levels. 0.33F CXN Output Current The MAX1759 is guaranteed to deliver a regulated 3.3V at 100mA continuous, from a +2.5V input. Peaks up to 200mA are acceptable as long as the current is 100mA (RMS). VOUT = 2.5V OUT VIN = 1.6V TO 5.5V 10F IN 100k 10F MAX1759 POK R1 76.8k SHDN Output Voltage Ripple The MAX1759 proprietary control scheme automatically chooses between voltage doubling and voltage stepdown to maintain output voltage regulation over various load currents and VIN to VOUT voltage differentials. When VIN is lower than VOUT, the charge pump always operates in voltage-doubler mode. It regulates the output voltage by modulating the charge delivered by the transfer capacitor. When VIN is higher than VOUT, the charge pump operates in voltage step-down mode, but may revert to voltage-doubler mode if necessary to maintain regulation under load. While operating in step-down mode, the output voltage ripple is typically much lower than it is in voltage-doubler mode (see Typical Operating Characteristics). CXP FB GND PGND R2 75k Figure 3. Using External Feedback for Regulated 2.5V Output Table 1. Capacitor Selection OUTPUT CURRENT (mA) CAPACITOR VALUE CIN (F) CX (F) 100 10 100 4.7 50 2.2 COUT (F) VIN = 2.5V VIN = 4.2V 0.33 10 40 20 0.22 4.7 80 60 0.1 2.2 100 80 Applications Information PC Board Layout The MAX1759 is a high-frequency switched-capacitor voltage regulator. For best circuit performance, use a ground plane and keep CIN, CX, COUT, and feedback resistors (if used) close to the device. If using external feedback, keep the feedback node as small as possible by positioning the feedback resistors very close to FB. Suggested PC component placement and board layout are shown in Figures 4a and 4b. Chip Information TRANSISTOR COUNT: 1802 8 OUTPUT RIPPLE (mV) _______________________________________________________________________________________ Buck/Boost Regulating Charge Pump in MAX SHDN SHDN R3 R2 R1 VOUT VIN U1 C1 MAX1759 POK POK VOUT VIN C3 C2 GND PLANE Figure 4a. MAX1759 Component Placement Guide GND PLANE Figure 4b. MAX1759 Recommended PC Board Layout _______________________________________________________________________________________ 9 Buck/Boost Regulating Charge Pump in MAX 10LUMAX.EP MAX1759 Package Information Note: The MAX1759 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. 10 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products. Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: Maxim Integrated: MAX1759EUB+ MAX1759EUB+T MAX1759EUB MAX1759EUB-T