PART TOP VIEW. OUT 3.3V AT 100mA POK. Maxim Integrated Products 1

Transcription

1 9-600; Rev ; 6/00 General Description The 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 operates over a wide +.6V to +5.5V input voltage range and generates a fixed.v or adjustable (.5V to 5.5V) output (Dual Mode ). Maxim s unique charge-pump architecture allows the input voltage to be higher or lower than the regulated output voltage. Despite its high.5mhz operating frequency, the maintains low 50µA 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 00mA (min) output current from a +.5V input. For added flexibility, the also includes an open-drain power-ok () output that signals when the output voltage is in regulation. The is available in a space-saving 0-pin µmax package that is.09mm high and half the size of an 8-pin SO. Li+ Battery-Powered Applications Miniature Equipment Backup Battery Boost Converters Translators Applications Buck/Boost Regulating Features Regulated Output Voltage (Fixed.V or Adjustable.5V to 5.5V) 00mA Guaranteed Output Current +.6V to +5.5V Input Voltage Range Low 50µA Quiescent Supply Current µa Shutdown Mode Load Disconnected from Input in Shutdown High.5MHz Operating Frequency Uses Small Ceramic Capacitors Short-Circuit Protection and Thermal Shutdown Small 0-Pin µmax Package PART EUB Ordering Information TEMP. RANGE -40 C to +85 C P-PACKAGE 0 µmax Typical Operating Circuit Pin Configuration C X TOP VIEW +.6V TO +5.5V CXN CXP.V AT 00mA 0 FB C C 9 8 CXP ON OFF FB GND PGND POWER OK GND 4 5 µmax 7 6 CXN PGND Dual Mode is a trademark of Maxim Integrated Products. Maxim Integrated Products For price, delivery, and to place orders, please contact Maxim Distribution at , or visit Maxim s website at

2 ABSOLUTE MAXIMUM RATGS,, FB,, to GND...-0.V to +6V PGND to GND...±0.V CXN to GND...-0.V to (V + 0.V) CXP to GND...-0.V to (the greater of V or V ) + V Short to GND...Indefinite Continuous Power Dissipation (T A = +70 C) 0-Pin µmax (derate 5.6mW/ C above +70 C)...444mW Operating Temperature Range C to +85 C Junction Temperature C Storage Temperature Range C to +50 C Lead Temperature (soldering, 0s) 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 (Circuit of Figure, V = V = V, FB = PGND = GND, C = 0µF, C X = 0.µF, C = 0µF, T A = 0 C to +85 C, unless otherwise noted. Typical values are at T A = +5 C.) PARAMETER SYMBOL CONDITIONS M TYP MAX UNITS Input Voltage Range V V Input Undervoltage Lockout Voltage V UVLO V Output Voltage Adjustment Range.6V V 5.5V V Output Voltage V V V 5.5V, ma I LOAD 50mA.7..4 V.5V V 5.5V, ma I LOAD 00mA.7..4 Maximum Output Current I LOAD,MAX.5V V 5.5V 00 ma Transient Load Current I LOAD 00mA (RMS) 00 ma Quiescent Supply Current I Q V = V = 4V, V FB = 0, stepping down V = V = V, V FB = 0, stepping up µa Shutdown Supply Current I Q,.6V V 5.5V, V = 0 5 µa Leakage Current into in Shutdown V = V, V =.V, V = 0 5 µa Logic Input Voltage V IL.6V V 5.5V 0.5 V V IH.6V V 5.5V 0.7 V V Input Leakage Current I V = 5.5V - µa FB Regulation Voltage V FB V =.65V, V =.V V FB Input Current V FB =.7V 5 00 na FB Dual-Mode Threshold Internal feedback mv External feedback mv Trip Voltage Falling edge at FB.0.. V Output Low Voltage V OL I SK = 0.5mA, V = V 5 00 mv Leakage Current V = 5.5V, V FB =.7V µa Switching Frequency f OSC.6V V 5.5V, V FB = V..5.8 MHz Output Short-Circuit Current V = 0,.5V V 5.5V, foldback current limit 0 ma Thermal Shutdown Temperature Rising temperature 60 C Thermal Shutdown Hysteresis 0 C Efficiency V =.6V, I LOAD = 0mA 90 %

3 ELECTRICAL CHARACTERISTICS (Circuit of Figure, V = V = V, FB = PGND = GND, C = 0µF, C X = 0.µF, C = 0µF, T A = -40 C to +85 C, unless otherwise noted.) (Note ) PARAMETER SYMBOL CONDITIONS M MAX UNITS Input Voltage Range V V Input Undervoltage Lockout Voltage V V 5.5V, 0 I LOAD 50mA.5.45 V Output Voltage V.5V V 5.5V, 0 I LOAD 00mA.5.45 V Output Voltage Adjustment Range V Maximum Output Current I LOAD,MAX.5V V 5.5V 00 ma V = V = 4V, V FB = 0 90 Quiescent Supply Current I Q µa V = V =.5V, V FB = 0 80 Shutdown Supply Current I Q,.6V V 5.5V, V = 0 6 µa Leakage Current into in Shutdown V UVLO V 5 µa V IL.6V V 5.5V 0. V V Input Logic Voltage V IH.6V V 5.5V 0.7 V V Input Leakage Current I V = 5.5V - µa FB Regulation Voltage V FB V =.65V, V =.V V FB Input Bias Current V FB =.7V 00 na FB Dual Mode Threshold.6V V 5.5V V = V, V =.V, V = 0 Internal feedback External feedback 40 mv 00 mv Trip Voltage Falling edge at FB.0. V Output Low Voltage V OL I SK = 0.5mA, V = V 00 mv Leakage Current V = 5.5V 0. µa Switching Frequency f OSC.6V V 5.5V, V FB = V..9 MHz Note : Specifications to -40 C are guaranteed by design and are not production tested.

4 QUIESCENT CURRENT (µa) Typical Operating Characteristics (Circuit of Figure, C = 0µF, C X = 0.µF, C = 0µF, V =.V, V =.5V, T A = +5 C, unless otherwise noted.) PUT VOLTAGE RIPPLE (mv) , PUT VOLTAGE RIPPLE vs. PUT VOLTAGE I = 0mA I = 00mA I = 50mA PUT VOLTAGE (V) 00 0 QUIESCENT CURRENT vs. PUT VOLTAGE toc0 toc04 PUT VOLTAGE (V) PUT VOLTAGE (V) PUT VOLTAGE vs. LOAD CURRENT LOAD CURRENT (ma) STARTUP PUT VOLTAGE (V < V ) R LOAD = Ω toc0 toc05 EFFICIENCY (%) EFFICIENCY vs. PUT VOLTAGE I = 0mA I = 50mA PUT VOLTAGE (V) I = 00mA TYPICAL SWITCHG WAVEFORMS (V < V ) R LOAD = Ω V = 4.V toc0 toc06 NO LOAD PUT VOLTAGE (V) TYPICAL SWITCHG WAVEFORMS (V > V ) PUT VOLTAGE (V) LOAD-TRANSIENT RESPONSE (V < V ) 5µs/div CH: V, 0mV/div, AC-COUPLED CH: V CXP, 5V/div CH: V, 50mV/div, AC-COUPLED LOAD-TRANSIENT RESPONSE (V > V ) R LOAD = Ω V =.5V toc07 toc08 toc09 LOAD STEP: 0mA TO 00mA V = 4.V LOAD STEP: 0mA TO 00mA V =.5V 5µs/div 00µs/div 00µs/div CH: V, 0mV/div, AC-COUPLED CH: V, 0mV/div, AC-COUPLED CH: V, 0mV/div, AC-COUPLED CH: V CXP, 5V/div CH: I, 00mA/div CH: I, 00mA/div CH: V, 50mV/div, AC-COUPLED 4

5 Typical Operating Characteristics (continued) (Circuit of Figure, C = 0µF, C X = 0.µF, C = 0µF, V =.V, V =.5V, T A = +5 C, unless otherwise noted.) LE-TRANSIENT RESPONSE R LOAD = Ω toc0 TURN-ON/OFF RESPONSE (V = 4.V) R LOAD = Ω V = 4.V toc TURN-ON/OFF RESPONSE (V =.5V) R LOAD = Ω V =.5V toc -4.V 00µs/div CH: V, 0mV/div, AC-COUPLED CH: V, V/div, AC-COUPLED -.5V 4 CH: V,V/div CH: I, 00mA/div CH: V, 5V/div CH4: V, 5V/div 500µs/div 4 500µs/div CH: V,V/div CH: I, 00mA/div CH: V, 5V/div CH4: V, 5V/div Pin Description P NAME FUNCTION, 4 Open-Drain Power-OK Output. is high impedance when output voltage is in regulation. sinks current when V FB falls below.v. Connect a 0kΩ to MΩ pull-up resistor from to V for a logic signal. Ground or leave unconnected if not used. is high impedance in shutdown. Shutdown Input. Drive high for normal operation; drive low for shutdown mode. is high impedance in shutdown. Input Supply. Connect both pins together and bypass to GND with a ceramic capacitor (see Capacitor Selection section). 5 GND Ground. Connect GND to PGND with a short trace. 6 PGND Power Ground. Charge-pump current flows through this pin. 7 CXN Negative Terminal of the Charge-Pump Transfer Capacitor 8 CXP Positive Terminal of the Charge-Pump Transfer Capacitor 9 Power Output. Bypass to GND with an output filter capacitor. 0 FB Dual-Mode Feedback. Connect FB to GND for.v output. Connect to an external resistor divider to adjust the output voltage from.5v to 5.5V. 5

6 Detailed Description The s unique charge-pump architecture allows the input voltage to be higher or lower than the regulated output voltage. Internal circuitry senses V and V and determines whether V must be stepped up or stepped down to produce the regulated output. When V is lower than V, the charge pump operates as a regulated step-up voltage doubler. When V is higher than V, 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 to (see Figures and ). Although V is greater than V, this scheme may not allow the to regulate the output under heavy loads. In this case, the 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 (C X ) to the load (see Figure ). 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. Shutdown Mode Driving low places the in shutdown mode. This disables the charge-pump switches, oscillator, and control logic, reducing quiescent current to µa. The output is high impedance in shutdown and is disconnected from the input. The output is high impedance in shutdown. Undervoltage Lockout The undervoltage lockout feature deactivates the device when the input voltage falls below V. Power-OK Output is an open-drain output that sinks current when the regulator feedback voltage falls below.v. 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 0kΩ to MΩ pull-up resistor from to may be used to provide a logic output. Connect to GND or leave unconnected if not used. Soft-Start and Short-Circuit Protection The features foldback short-circuit protection. This circuitry provides soft-start by limiting inrush current during startup and limits the output current to 0mA (typ) if the output is short-circuited to ground. ON +.6V TO +5.5V 0µF OFF CXN FB 0.µF CXP GND PGND Figure. Typical Application Circuit Thermal Shutdown The features thermal shutdown with temperature hysteresis. When the die temperature exceeds 60 C, the device shuts down. When the die cools by 0 C, the 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. Design Procedure Setting the Output Voltage The dual-mode feedback controller selects between the internally set.v regulated output or an external resistive divider that allows adjustment of the output voltage from.5v to 5.5V. Connect FB to GND for a regulated.v output. For an adjustable output, connect a resistive divider between and GND. To ensure feedback-loop stability and to minimize error due to FB pin bias currents, the resistive divider current should be approximately 5µA. In the following equation, choose R in the 50kΩ to 00kΩ range, and calculate R from the following formula (Figure ): R = R [(V / V FB ) - ].V AT 00mA 00k 0µF POWER OK and V = V FB (R + R) / R where V is the desired output voltage from.5v to 5.5V, and V FB is the internal regulation voltage, nominally.5v. The circuit of Figure generates a regulated.5v, using external standard % resistor values. Surface-mount resistors should be placed close to the, less than 5mm away from FB (see the PC Board Layout section). 6

7 , 4 PGND 6 CXN 7 CXP 8 S S 9 R BUCK-BOOST CONTROL R BIAS.5MHz OSC ENABLE FB 0.5V N -LOW GND 5.V 0.V Figure. Functional Diagram 7

8 Capacitor Selection Optimize the charge-pump circuit for physical size, output current, and output ripple by selecting capacitors C, C X, and C. See Table for suggested capacitor values. Note that capacitors must have low ESR ( 0mΩ) 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 µf ceramic in parallel with a 0µF tantalum capacitor. The ceramic capacitor s low ESR will help keep output ripple within acceptable levels. Output Voltage Ripple The proprietary control scheme automatically chooses between voltage doubling and voltage stepdown to maintain output voltage regulation over various load currents and V to V voltage differentials. When V is lower than V, the charge pump always operates in voltage-doubler mode. It regulates the output voltage by modulating the charge delivered by the transfer capacitor. When V is higher than V, 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). Output Current The is guaranteed to deliver a regulated.v at 00mA continuous, from a +.5V input. Peaks up to 00mA are acceptable as long as the current is 00mA (RMS). Applications Information PC Board Layout The is a high-frequency switched-capacitor voltage regulator. For best circuit performance, use a ground plane and keep C, C X, C, 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. TRANSISTOR COUNT: 80 Chip Information V =.6V TO 5.5V 0µF CXN GND 0.µF CXP FB PGND 0µF R 76.8k R 75k V =.5V 00k Figure. Using External Feedback for Regulated.5V Output Table. Capacitor Selection PUT CURRENT (ma) C (µf) CAPACITOR VALUE C X (µf) C (µf) PUT RIPPLE (mv) V =.5V V = 4.V

9 V R R R U C C C V V V GND PLANE GND PLANE Figure 4a. Component Placement Guide Figure 4b. Recommended PC Board Layout 9

10 Package Information 0LUMAX.EP Note: The 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. 0 Maxim Integrated Products, 0 San Gabriel Drive, Sunnyvale, CA Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.