1.5µA IQ, Step-Up DC-DC Converters in Thin SOT23-5

Transcription

1 ; Rev ; 7/1 1.5µA IQ, Step-Up DC-DC Converters General Description The compact, high-efficiency, step-up DC-DC converters are available in tiny, 5- pin thin SOT3 packages. They feature an extremely low 1.5µA quiescent supply current to ensure the highest possible light-load efficiency. Optimized for operation from one to two alkaline or nickel-metal-hydride (NiMH) cells, or a single Li+ cell, these devices are ideal for applications where extremely low quiescent current and ultra-small size are critical. Built-in synchronous rectification significantly improves efficiency and reduces size and cost by eliminating the need for an external Schottky diode. All three devices feature a.5ω N-channel power switch. The MAX17/ MAX174 also feature proprietary noise-reduction circuitry, which suppresses electromagnetic interference (EMI) caused by the inductor in many step-up applications. The family offers different combinations of fixed or adjustable outputs, shutdown, and EMI reduction (see Selector Guide). Pagers Remote Controls Remote Wireless Transmitters Personal Medical Devices Digital Still Cameras 1µH Applications Single-Cell Battery- Powered Devices Low-Power Hand-Held Instruments MP3 Players Personal Digital Assistants (PDA) Typical Operating Circuit Features Up to 9% Efficiency No External Diode or FETs Needed 1.5µA Quiescent Supply Current.1µA Logic-Controlled Shutdown ±1% Output Voltage Accuracy Fixed Output Voltage (MAX174) or Adjustable Output Voltage (MAX17/MAX173) Up to 15mA Output Current.8V to 5.5V Input Voltage Range.91V Guaranteed Startup (MAX17/MAX174) Internal EMI Suppression (MAX17/MAX174) Thin SOT3-5 Package (1.1mm max Height) PART MAX17EZK-T MAX173EZK-T MAX174EZK7-T MAX174EZK3-T MAX174EZK33-T MAX174EZK5-T PART MAX17EZK MAX173EZK MAX174EZK7 Adjustable Adjustable Fixed.7 MAX174EZK3 Fixed 3. MAX174EZK33 Fixed 3.3 MAX174EZK5 Fixed 5. Ordering Information TEMP. RANGE -4 C to +85 C -4 C to +85 C -4 C to +85 C -4 C to +85 C -4 C to +85 C -4 C to +85 C PUT (V) PIN- PACKAGE 5 SOT3 5 SOT3 5 SOT3 5 SOT3 5 SOT3 5 SOT3 Selector Guide No TOP MARK ADQF ADQG ADQH ADQI ADQJ ADQK DAMPING No Pin Configurations IN.8V TO 5.5V TOP VIEW 1 5 ON OFF MAX V AT UP TO 15mA FB MAX THIN SOT3-5 Pin Configurations are continued at end of data sheet. Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at , or visit Maxim s website at

2 ABSOLUTE MAXIMUM RATINGS,,, to...-.3v to +6V FB to...-.3v to (V +.3V), Current...1A Continuous Power Dissipation (T A = +7 C) 5-Pin Thin SOT3 (derate 7.1mW/ C above +7 C)...571mW 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 Operating Temperature Range...-4 C to +85 C Junction Temperature C Storage Temperature Range C to +15 C Lead Temperature (soldering, 1s) C (V = 1.V, V = 3.3V (MAX17/MAX173), V = V (NOM) (MAX174), =, R L =, T A = C to +85 C, unless otherwise noted. Typical values are at T A = +5 C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Minimum Input Voltage MAX17/MAX174.8 V Operating Input Voltage V IN T A = +5 C MAX17/MAX MAX173 (Note ) V Minimum Startup Input Voltage T A = +5 C, MAX17/MAX R L = 3kΩ MAX173 (Note ) V MAX174EZK7 T A = +5 C T A = C to +85 C Output Voltage V MAX174EZK3 T A = +5 C T A = C to +85 C MAX174EZK33 T A = +5 C T A = C to +85 C V MAX174EZK5 T A = +5 C T A = C to +85 C Output Voltage Range V MAX17/MAX V Feedback Voltage V FB MAX17/MAX173 T A = +5 C T A = C to +85 C V Feedback Bias Current I FB MAX17/MAX173 T A = +5 C 1.5 T A = +85 C. na N-Channel On-Resistance R DS(ON) V forced to 3.3V.5 1. Ω P-Channel On-Resistance R DS(ON) V forced to 3.3V 1.. Ω N-Channel Switch Current Limit I LIM V forced to 3.3V ma Switch Maximum On-Time t ON µs Synchronous Rectifier Zero- Crossing Current V forced to 3.3V 5 35 ma Quiescent Current into (Notes 3, 4) µa Shutdown Current into MAX173/MAX174 T A = +5 C.1.5 (Notes 3, 4) T A = +85 C.1 µa Quiescent Current into MAX17/MAX174 T A = +5 C.1.5 (Note 4) T A = +85 C.1 µa

3 ELECTRICAL CHARACTERISTICS (continued) (V = 1.V, V = 3.3V (MAX17/MAX173), V = V (NOM) (MAX174), =, R L =, T A = C to +85 C, unless otherwise noted. Typical values are at T A = +5 C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Shutdown Current into MAX174 (Note 4) T A = +5 C.1.5 T A = +85 C.1 µa Voltage Threshold V IL MAX173/MAX V IH MAX173/MAX mv Input Bias Current MAX173/MAX174, T A = +5 C 1 V = 5.5V T A = +85 C 7 na ELECTRICAL CHARACTERISTICS (V = 1.V, V = 3.3V (MAX17/MAX173), V = V (NOM) (MAX174), =, R L =, T A = -4 C to +85 C, unless otherwise noted.) (Note 1) O utp ut V ol tag e PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS V MAX174EZK MAX174EZK MAX174EZK MAX174EZK O utp ut V ol tag e Rang e V MAX17/MAX V Feedback Voltage V FB MAX17/MAX V N-Channel On-Resistance R DS(ON) V forced to 3.3V 1. Ω P-Channel On-Resistance R DS(ON) V forced to 3.3V. Ω N-Channel Switch Current Limit I LIM V forced to 3.3V 4 6 ma Switch Maximum On-Time t ON µs V Synchronous Rectifier Zero- Crossing Current V forced to 3.3V 5 35 ma Quiescent Current into (Notes 3,4) 3.6 µa Voltage Threshold V IL MAX173/MAX V IH MAX173/MAX174 8 mv Note 1: Limits are 1% production tested at T A = +5 C. Limits over the operating temperature range are guaranteed by design. Note : Guaranteed with the addition of a Schottky MBR5L external diode between and when using the MAX173 with only one cell, and assumes a.3v voltage drop across the Schottky diode (see Figure 3). Note 3: Supply current is measured with an ammeter between the output and pin. This current correlates directly with actual battery supply current, but is reduced in value according to the step-up ratio and efficiency. Note 4: V forced to the following conditions to inhibit switching: V = 1.5 V (NOM) (MAX174), V = 3.465V (MAX17/MAX173). 3

4 EFFICIENCY (%) I(MAX) (ma) Typical Operating Characteristics (Figure 3 (MAX173), Figure 7 (MAX17), Figure 8 (MAX174), V = V IN = 1.5V, L = 1µH, C IN = 1µF, C = 1µF, T A = +5 C, unless otherwise noted.) EFFICIENCY vs. LOAD CURRENT (V = 5.V) V IN =.V MAXIMUM PUT CURRENT vs. INPUT VOLTAGE V =.5V V IN = 3.3V V IN = 4.V V IN = 1.V V IN = 1.5V L = DO LOAD CURRENT (ma) V = 3.3V V = 5.V MAX17 toc1 MAX17 toc4 EFFICIENCY (%) STARTUP VOLTAGE (V) 1 9 V IN =.V EFFICIENCY vs. LOAD CURRENT (V = 3.3V) RESISTIVE LOAD V = 5.V V IN =.5V V IN = 1.V V IN = 1.5V L = DO LOAD CURRENT (ma) STARTUP VOLTAGE vs. LOAD CURRENT MAX17 toc MAX17 toc5 EFFICIENCY (%) QUIESCENT CURRENT (µa) V IN = 1.V L = DO LOAD CURRENT (ma) EFFICIENCY vs. LOAD CURRENT (V =.5V) V IN = 1.5V QUIESCENT CURRENT INTO vs. PUT VOLTAGE NO LOAD V IN =.V MAX17 toc3 MAX17 toc INPUT VOLTAGE (V) LOAD CURRENT (ma) PUT VOLTAGE (V) STARTUP VOLTAGE vs. TEMPERATURE SWITCHING WAVEFORMS NO LOAD MAX17 toc7 MAX17 toc8 I 5mA/div STARTUP VOLTAGE (V) V 5mV/div V V/div TEMPERATURE ( C) 1µs/div I = 5mA, V = 5.V, V IN = 3.3V 4

5 Typical Operating Characteristics (continued) (Figure 3 (MAX173), Figure 7 (MAX17), Figure 8 (MAX174), V = V IN = 1.5V, L = 1µH, C IN = 1µF, C = 1µF, T A = +5 C, unless otherwise noted.) 3.3V 5mA LOAD-TRANSIENT RESPONSE A: V, 5mV/div B: I, ma/div µs/div SHUTDOWN THRESHOLD (mv) MAX17 toc9 A B 5V V SHUTDOWN INPUT THRESHOLD vs. TEMPERATURE FALLING EDGE RISING EDGE SHUTDOWN RESPONSE 1ms/div V IN = 3.3V, V = 5.V, R = 1Ω MAX17 toc11 MAX17 toc1 V V/div V 1V/div TEMPERATURE ( C) Pin Description MAX17 PIN MAX173 MAX174 NAME FUNCTION 1 1 Battery Input and Damping Switch Connection 1 3 Shutdown Input. Drive high for normal operation. Drive low for shutdown. Ground 3 3 FB Feedback Input to Set Output Voltage. Use a resistor-divider network to adjust the output voltage. See Setting the Output Voltage section Power Output. also provides bootstrap power to the IC Internal N-channel MOSFET Switch Drain and P-Channel Synchronous Rectifier Drain 5

6 MAX173 FB ERROR COMPARATOR 1.35V REFERENCE STARTUP CIRCUITRY CONTROL LOGIC DRIVER CURRENT LIMIT ZERO- CROSSING DETECTOR P N Figure 1. MAX173 Simplified Functional Diagram Detailed Description The compact, high-efficiency, step-up DC-DC converters are guaranteed to start up with voltages as low as.91v and operate with an input voltage down to.8v. Consuming only 1.5µA of quiescent current, these devices include a built-in synchronous rectifier that reduces cost by eliminating the need for an external diode and improves overall efficiency by minimizing losses in the circuit (see Synchronous Rectification section). The MAX17/MAX174 feature a clamp circuit that reduces EMI due to inductor ringing. The MAX173/MAX174 feature an active-low shutdown that reduces quiescent supply current to.1µa. The MAX17/MAX173 have an adjustable output voltage, while the MAX174 is available with four fixed-output voltage options (see Selector Guide). Figure 1 is the MAX173 simplified functional diagram and Figure is the MAX174 simplified functional diagram. PFM Control Scheme A forced discontinuous, current-limited, pulse-frequencymodulation (PFM) control scheme is a key feature of the. This scheme provides ultra-low quiescent current and high efficiency over a wide output current range. There is no oscillator; the inductor current is limited by the.5a N-channel current limit or by the 5µs switch maximum on-time. Following each on cycle, the inductor current must ramp to zero before another cycle may start. When the error comparator senses that the output has fallen below the regulation threshold, another cycle begins. Synchronous Rectification The internal synchronous rectifier eliminates the need for an external Schottky diode, thus reducing cost and board space. While the inductor discharges, the P- channel MOSFET turns on and shunts the MOSFET body diode. As a result, the rectifier voltage drop is significantly reduced, improving efficiency without the addition of external components. Low-Voltage Startup Circuit The contain a low-voltage startup circuit to control DC-DC operation until the output voltage exceeds 1.5V (typ). The minimum start- 6

7 R R 1 MAX174 ERROR COMPARATOR 1.35V REFERENCE STARTUP CIRCUITRY CONTROL LOGIC DAMPING SWITCH DRIVER CURRENT LIMIT ZERO- CROSSING DETECTOR P N Figure. MAX174 Simplified Functional Diagram 1.V TO V 1µF 1µH MAX173 Figure 3. MAX173 Single-Cell Operation V = 3.6V up voltage is a function of load current (see Typical Operating Characteristics). This circuit is powered from the pin for the MAX17/MAX174, guaranteeing startup at input voltages as low as.91v. The MAX173 FB D1 R.37MΩ R1 1.4MΩ 1µF lacks a pin; therefore, this circuit is powered through the pin. Adding a Schottky diode in parallel with the P-channel synchronous rectifier allows for startup voltages as low as 1.V for the MAX173 (Figure 3). The external Schottky diode is not needed for input voltages greater than 1.8V. Once started, the output maintains the load as the battery voltage decreases below the startup voltage. Shutdown (MAX173/MAX174) The MAX173/MAX174 enter shutdown when the pin is driven low. During shutdown, the body diode of the P-channel MOSFET allows current to flow from the battery to the output. V falls to approximately V IN -.6V and remains high impedance. Shutdown can be pulled as high as 6V, regardless of the voltage at or. For normal operation, connect to the input. 7

8 MAX17 MAX174 PDRV TIMING CIRCUIT DAMP NDRV DAMPING SWITCH Figure 4. Simplified Diagram of Damping Switch 1V/div P N V V IN 1V/div 1µs/div Figure 5. Ringing Without Damping Switch (MAX173) /Damping Switch (MAX17/MAX174) The MAX17/MAX174 include an internal damping switch (Figure 4) to minimize ringing at and reduce EMI. When the energy in the inductor is insufficient to supply current to the output, the capacitance and inductance at form a resonant circuit that causes ringing. The damping switch supplies a path to quickly dissipate this energy, suppressing the ringing at. This does not reduce the output ripple, but does reduce EMI with minimal impact on efficiency. Figures 5 and 6 show the node voltage waveform without and with the damping switch, respectively. Design Procedure Setting the Output Voltage (MAX17/MAX173) The output voltage can be adjusted from V to 5.5V using external resistors R1 and R (Figure 7). Since FB leakage is na (max), select feedback resistor R1 in the 1kΩ to 1MΩ range. Calculate R as follows: where V FB = 1.35V. 1µs/div Figure 6. Ringing With Damping Switch (MAX17/MAX174) V R R = 1 1 V FB 8

9 INPUT.8V TO V 1µH 1µF MAX17 Figure 7. Adjustable Output Circuit Inductor Selection The control scheme of the MAX17/MAX173/ MAX174 permits flexibility in choosing an inductor. A 1µH inductor value performs well in most applications. Smaller inductance values typically offer smaller physical size for a given series resistance, allowing the smallest overall circuit dimensions. Circuits using larger inductance values may start up at lower battery voltages, provide higher efficiency, and exhibit less ripple, but they may reduce the maximum output current. This occurs when the inductance is sufficiently large to prevent the maximum current limit (I LIM ) from being reached before the maximum on-time (t ON(MAX) ) expires. Table 1. Suggested Inductors and Suppliers MANUFACTURER Coilcraft Murata Sumida INDUCTOR FB DO168 Series DO166 Series LQH4C Series CDRH4D18 Series CR3 Series CMD4D6 Series PUT V TO 5.5V R 1µF R1 PHONE WEBSITE For maximum output current, choose the inductor value so that the controller reaches the current-limit before the maximum on-time is triggered: L < V ton( MAX) ILIM where the maximum on-time is typically 5µs, and the current limit (I LIM ) is typically 5mA (see Electrical Characteristics table). For larger inductor values, determine the peak inductor current (I PEAK) by: V ton( MAX) IPEAK = L INPUT.8V TO V 1µH C1 1µF ON OFF MAX174 Figure 8. MAX174 Standard Application Circuit PUT V (NOM) C 1µF The inductor s incremental saturation current rating should be greater than the peak switching current. However, it is generally acceptable to bias the inductor into saturation by as much as %, although this will slightly reduce efficiency. Table 1 lists suggested inductors and suppliers. Maximum Output Current The maximum output current depends on the peak inductor current, the input voltage, the output voltage, and the overall efficiency (η): Sumitomo/ Daidoo Electronics Toko CXLD14 Series 3DF Type D41F Type +81 (6) V I I ( MAX) = 1 PEAK V η 9

10 Table. Suggested Surface-Mount Capacitors and Manufacturers (C1 and C) MANUFACTURER AVX Kemet CAPACITOR VALUE For most applications, the peak inductor current equals the current limit. However, for applications using large inductor values or low input voltages, the maximum ontime limits the peak inductor current (see Inductor Selection section). Capacitor Selection Choose input and output capacitors to supply the input and output peak currents with acceptable voltage ripple. The input filter capacitor (C IN ) reduces peak currents drawn from the battery and improves efficiency. Low equivalent series resistance (ESR) capacitors are recommended. Ceramic capacitors have the lowest ESR, but low ESR tantalum or polymer capacitors offer a good balance between cost and performance. Output voltage ripple has two components: variations in the charge stored in the output capacitor with each pulse, and the voltage drop across the capacitor s ESR caused by the current into and out of the capacitor: VRIPPLE = VRIPPLE( C) + VRIPPLE( ESR) VRIPPLE( ESR) I PEAK RESR( C) 1 L VRIPPLE( C) ( V - V ) C ( I PEAK -I ) DESCRIPTION 1µF to 1µF X7R Ceramic 1µF to 33µF TAJ Tantalum Series TPS Tantalum Series 1µF to µf X5R/X7R Ceramic 1µF to 33µF T494 Tantalum Series 68µF to 33µF T5 Tantalum Series Sanyo 33µF to 33µF TPC Polymer Series Taiyo Yuden 33µF to 33µF X5R/X7R Ceramic TDK 1µF to 1µF X7R Ceramic Vishay Sprague 1µF to 33µF 594D Tantalum Series 595D Tantalum Series PHONE WEBSITE where I PEAK is the peak inductor current (see Inductor Selection section). For ceramic capacitors, the output voltage ripple is typically dominated by V RIPPLE(C). For example, a 1µF ceramic capacitor and a 1µH inductor typically provide 75mV of output ripple when stepping up from 3.3V to 5V at 5mA. Low input-to-output voltage differences (i.e. two cells to 3.3V) require higher output capacitor values. Capacitance and ESR variation of temperature should be considered for best performance in applications with wide operating temperature ranges. Table lists suggested capacitors and suppliers. PC Board Layout Considerations Careful PC board layout is important for minimizing ground bounce and noise. Keep the IC s pin and the ground leads of the input and output capacitors less than.in (5mm) apart using a ground plane. In addition, keep all connections to FB (MAX17/MAX173 only) and as short as possible. TRANSISTOR COUNT: Chip Information 1

11 TOP VIEW FB 1 5 MAX THIN SOT3-5 Pin Configurations (continued) 1 5 MAX THIN SOT3-5 Package Information THIN SOT3.EPS 11

12 Package Information (continued) 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. 1 Maxim Integrated Products, 1 San Gabriel Drive, Sunnyvale, CA Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.