19-0459; Rev 1; 1/99 NUAL KIT MA ATION U EET L H A S V E S DATA W O L L FO Low-Profile, 5V/12V or Adjustable, Step-Up DC-DC Converters for Flash Memory/PCMCIA Cards The MAX606/MAX607 are the smallest CMOS, step-up DC-DC converters available for flash memory and PC (PCMCIA) cards. They switch at up to 1MHz, permitting the entire circuit to fit in 0.25in 2 , yet remain under 1.35mm high to fit Type 1, 2, and 3 card standards. These devices operate from a 3V to 5.5V input and provide a ±4% accurate output that is preset to 5V or 12V, or adjustable from VIN to 12.5V. They can provide up to 180mA of output current at 5V. The MAX606 switches at up to 1MHz and fits Type 1 (thinnest standard) flash memory and PCMCIA cards. It uses a thin, 1.19mm high, 5µH inductor and small, 0.68µF output capacitors. The entire circuit fits in 0.25in2 and is less than 1.35mm high. The MAX607 switches at up to 500kHz, fitting Type 2 and 3 cards, as well as hand-held devices where height requirements are not as critical. It uses less board area than the MAX606, fitting in 0.16in 2, but requires 2.5mm of height. It also has a lower no-load supply current than the MAX606. Both devices use a unique control scheme that optimizes efficiency over all input and output voltages. Other features include 1µA logic-controlled shutdown and usercontrolled soft-start to minimize inrush currents. ____________________________Features ♦ Lowest-Height Circuit (1.35mm max) ♦ ±4% Regulated Output (5V, 12V, or Adjustable) ♦ Up to 180mA Load Current ♦ 1MHz Switching Frequency (MAX606) ♦ 1µA Logic-Controlled Shutdown ♦ 3V to 5.5V Input Voltage Range ♦ Compact 8-Pin µMAX Package Ordering Information PART MAX606ESA MAX606EUA MAX607ESA MAX607EUA TEMP. RANGE -40°C to +85°C -40°C to +85°C -40°C to +85°C -40°C to +85°C PIN-PACKAGE 8 SO 8 µMAX 8 SO 8 µMAX The MAX606/MAX607 come in 8-pin µMAX and SO packages. The µMAX package uses half the board area of a standard 8-pin SO and has a maximum height of just 1.11mm. ________________________Applications PCMCIA Cards Memory Cards Typical Operating Circuit Single PCMCIA Slot Programming Digital Cameras INPUT +4.5V TO +5.5V Flash Memory Programming Hand-Held Equipment Pin Configuration 0.68µF 0.68µF ON/OFF 0.1µF SHDN 5µH IN LX TOP VIEW PGND 1 8 LX FB 2 7 OUT SHDN 3 6 SS IN 4 5 GND MAX606 MAX607 FB MAX606 OUT GND OUTPUT 12V @ 90mA 0.68µF x2 PGND SO/µMAX ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 1-800-835-8769. MAX606/MAX607 General Description MAX606/MAX607 Low-Profile, 5V/12V or Adjustable, Step-Up DC-DC Converters for Flash Memory/PCMCIA Cards ABSOLUTE MAXIMUM RATINGS IN to GND .................................................................-0.3V to +6V LX, OUT to GND .....................................................-0.3V to +15V PGND to GND.....................................................................±0.3V FB to GND ..................................................-0.3V to (VCC + 0.3V) SS, SHDN to GND ....................................................-0.3V to +6V Continuous Power Dissipation (TA = +70°C) µMAX (derate 4.10mW/°C above +70°C) ....................330mW SO (derate 5.88mW/°C above +70°C) .........................471mW Operating Temperature Range ...........................-40°C to +85°C Storage Temperature .......................................................+160°C Lead Temperature (soldering, 10sec) .............................+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 = 3.3V, GND = PGND = FB = 0V, SHDN = IN, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER CONDITIONS Supply Voltage MIN TYP 3.0 Undervoltage Lockout Threshold 2.4 MAX UNITS 5.5 V 2.8 V 3V < VIN < 5V, FB = IN, ILOAD = 0 to 180mA 4.8 5.0 5.2 4.5V < VIN < 5.5V, FB = GND, ILOAD = 0 to 120mA 11.5 12.0 12.5 FB Regulation Setpoint 0.1V < VFB < (VIN - 0.1V) 1.96 2.00 2.04 Adjustable Output Voltage Range 0.1V < VFB < (VIN - 0.1V) VIN Line Regulation VIN = 3V to 5.5V Output Voltage (Note 1) Switch On-Resistance Switch Off-Leakage 0.4 VLX = 12V Switch Current Limit SS Resistance 12.5 0.5 0.7 V SHDN = VIN, VSS = 150mV 30 45 V SHDN = VSS = 0 Quiescent Supply Current VOUT = 13V Shutdown Quiescent Current V SHDN = 0, OUT = IN OUT Input Current VOUT = 13V V V V % 1 Ω 10 µA 1.1 A 60 0.5 kΩ MAX606 250 500 MAX607 150 300 0.01 10 µA 80 µA MAX606 1.9 3.0 4.3 MAX607 3.8 6.0 8.6 Switch On-Time Constant (K) 3V < VIN < 5.5V (tON = K / VIN) Switch Off-Time Ratio 2V < (VOUT + 0.5V - VIN) < 8V (see PulseFrequency-Modulation Control Scheme section) SHDN Input Low Voltage VIN = 3V SHDN Input High Voltage VIN = 5.5V SHDN Input Current 0.3 µA µs-A 0.7 0.25VIN V V SHDN = 0 or VIN ±1 µA FB Input Low Voltage VIN = 3V to 5.5V. For VFB below this voltage, output regulates to 12V. 0.1 V FB Input High Voltage VIN = 3V to 5.5V. For VFB above this voltage, output regulates to 5V. FB Input Current VFB = 2.05V, VOUT = 13V 2 0.66VIN V VIN - 0.1 _______________________________________________________________________________________ V 200 nA Low-Profile, 5V/12V or Adjustable, Step-Up DC-DC Converters for Flash Memory/PCMCIA Cards (VIN = 3.3V, GND = PGND = FB = 0V, SHDN = IN, TA = -40°C to +85°C, unless otherwise noted.) (Note 2) PARAMETER CONDITIONS Supply Voltage MIN TYP 3.0 Undervoltage Lockout Threshold 2.4 MAX UNITS 5.5 V 2.8 V 3V < VIN < 5V, FB = IN, ILOAD = 0 to 135mA 4.75 5.25 4.5V < VIN < 5.5V, FB = GND, ILOAD = 0 to 90mA 11.4 12.6 FB Regulation Setpoint 0.1V < VFB < (VIN - 0.1V) 1.94 2.06 Adjustable Output Voltage Range 0.1V < VFB < (VIN - 0.1V) VIN 12.5 V 1 Ω 10 µA 0.55 1.25 A 30 60 Output Voltage (Note 1) Switch On-Resistance Switch Off-Leakage VLX = 12V Switch Current Limit V SHDN = VIN, VSS = 150mV SS Resistance V SHDN = VSS = 0 0.5 MAX606 500 MAX607 300 V V kΩ Quiescent Supply Current VOUT = 13V µA Shutdown Quiescent Current V SHDN = 0, OUT = IN OUT Input Current VOUT = 13V Switch On-Time Constant (K) 3V < VIN < 5.5V (tON = K / VIN) Switch Off-Time Ratio 2V < (VOUT + 0.5V - VIN) < 8V (see PulseFrequency-Modulation Control Scheme section) SHDN Input Low Voltage VIN = 3V SHDN Input High Voltage VIN = 5.5V SHDN Input Current V SHDN = 0 or VIN ±1 µA FB Input Low Voltage VIN = 3V to 5.5V. For VFB below this voltage, output regulates to 12V. 0.1 V FB Input High Voltage VIN = 3V to 5.5V. For VFB above this voltage, output regulates to 5V. FB Input Current VFB = 2.05V, VOUT = 13V 10 µA 85 µA MAX606 1.8 4.5 MAX607 3.5 9.0 0.3 0.7 0.25VIN 0.66VIN µs-V V V VIN - 0.1 V 200 nA Note 1: The load specification is guaranteed by DC parametric tests and is not production tested in circuit. Note 2: Specifications to -40°C are guaranteed by design, not production tested. _______________________________________________________________________________________ 3 MAX606/MAX607 ELECTRICAL CHARACTERISTICS Typical Operating Characteristics (VIN = 3.3V, TA = +25°C, unless otherwise noted.) MAX606 EFFICIENCY vs. OUTPUT CURRENT 50 40 10 MAX607 (VOUT = 12V) 0 3.0 3.5 4.0 4.5 5.0 5.5 0.01 40 0.1 1 10 100 A: VOUT = 12V, VIN = 3.3V B: VOUT = 5V, VIN = 3.3V C: VOUT = 12V, VIN = 5V D: VOUT = 5V, VIN = 5V 10 0 0.01 1000 0.1 1 10 100 OUTPUT CURRENT (mA) SHUTDOWN QUIESCENT CURRENT vs. TEMPERATURE SWITCH ON-TIME vs. INPUT VOLTAGE SWITCH OFF-TIME vs. OUTPUT VOLTAGE 0.6 0.5 0.4 0.3 0.2 2000 1500 MAX607 1000 0 -20 0 20 40 60 2500 D C 2000 A B 1500 1000 500 0 0 2.5 80 3000 MAX606 500 0.1 A: MAX607, VIN = 5V B: MAX606, VIN = 5V C: MAX607, VIN = 3.3V D: MAX606, VIN = 3V 3500 SWITCH OFF-TIME (ns) 0.7 2500 3.0 3.5 4.0 4.5 5.0 2 5.5 3 4 5 6 7 8 9 10 11 12 INPUT VOLTAGE (V) OUTPUT VOLTAGE (V) MAX606 NO-LOAD SUPPLY CURRENT vs. TEMPERATURE MAX607 NO-LOAD SUPPLY CURRENT vs. TEMPERATURE DIODE LEAKAGE CURRENT vs. TEMPERATURE VIN = 3.3V B C D A: VOUT = 12V, MBR0520 DIODE B: VOUT = 12V, MBR0540 DIODE C: VOUT = 5V, MBR0520 DIODE D: VOUT = 5V, MBR0540 DIODE 1000 A VIN = 3.3V 10,000 B C D MAX606/07-09 NO-LOAD SUPPLY CURRENT (µA) MAX606/7-07 A 1000 10,000 MAX606/7-08 TEMPERATURE (°C) A: VOUT = 12V, MBR0520 DIODE B: VOUT = 12V, MBR0540 DIODE C: VOUT = 5V, MBR0520 DIODE D: VOUT = 5V, MBR0540 DIODE 1000 4000 MAX606/7 TOC-05 3000 SWITCH ON-TIME (ns) SHUTDOWN IQ (µA) 50 OUTPUT CURRENT (mA) 0.8 10,000 60 INPUT VOLTAGE (V) FOR VIN = 3V, 3.3V, AND 5V 5 MINUTE WAIT BEFORE MEASUREMENT -40 70 20 1000 LEAKAGE CURRENT (µA) 0.9 2.5 MAX606/7 TOC04 2.0 A 30 A: VOUT = 12V, VIN = 3.3V B: VOUT = 5V, VIN = 3.3V C: VOUT = 12V, VIN = 5V D: VOUT = 5V, VIN = 5V 20 0 B C MAX606/7 TOC-06 100 D 80 30 MAX606 (VOUT = 12V) CIN = 2 x 1µF COUT = 4.7µF 90 B 60 200 1.0 100 A 70 EFFICIENCY (%) 300 C 80 MAX607 (VOUT = 5V) 500 400 D EFFICIENCY (%) 600 CIN = 2 x 1µF COUT = 4.7µF 90 MAX606/7 TOC02 MAX606 (VOUT = 5V) MAXIMUM OUTPUT CURRENT (mA) 100 MAX606/07toc01 700 MAX607 EFFICIENCY vs. OUTPUT CURRENT MAX606/7 TOC03 MAXIMUM OUTPUT CURRENT vs. INPUT VOLTAGE NO-LOAD SUPPLY CURRENT (µA) MAX606/MAX607 Low-Profile, 5V/12V or Adjustable, Step-Up DC-DC Converters for Flash Memory/PCMCIA Cards 100 MBR0520L 10 1 MBR0540 MBR0530 0.1 0.01 VOUT = VANODE = 12V 100 -40 -20 0 20 40 TEMPERATURE (˚C) 4 0.001 100 60 80 -40 -20 0 20 40 TEMPERATURE (˚C) 60 80 -40 -20 0 20 40 TEMPERATURE (°C) _______________________________________________________________________________________ 60 80 Low-Profile, 5V/12V or Adjustable, Step-Up DC-DC Converters for Flash Memory/PCMCIA Cards MAX607 MAXIMUM OUTPUT CURRENT vs. INDUCTOR VALUE 300 B 250 200 150 C 100 A: VOUT = 5V, VIN = 3.3V B: VOUT = 12V, VIN = 5V C: VOUT = 12V, VIN = 3.3V 50 0 1x100 A: VOUT = 5V, VIN = 3.3V B: VOUT = 12V, VIN = 5V C: VOUT = 12V, VIN = 3.3V 350 300 A 200 150 C 100 0 1400 A: MAX607 VOUT = 12V B: MAX606 VOUT = 12V C: MAX607 VOUT = 5V D: MAX606 VOUT = 5V 1200 1000 800 B A 600 VIN = 3.3V 400 50 1x101 1800 1600 B 250 20,800 MAX606/07-12a 350 400 START-UP DELAY (µs) A MAXIMUM OUTPUT CURRENT (mA) MAX606/07-10 MAXIMUM OUTPUT CURRENT (mA) 400 START-UP DELAY vs. SOFT START CAPACITOR MAX606/07-11 MAX606 MAXIMUM OUTPUT CURRENT vs. INDUCTOR VALUE 200 0 1x100 INDUCTOR VALUE (µH) 1x101 INDUCTOR VALUE (µH) MAX606 START-UP DELAY AND INRUSH CURRENT 1x101 1x102 1x103 1x104 D 1x105 SOFT-START CAPACITOR (pF) MAX607 START-UP DELAY AND INRUSH CURRENT 2V 12V SHDN 2V/div C OUTPUT 5V/div 2V 12V SHDN 2V/div OUTPUT 5V/div 400mA 200mA INPUT 200mA/div INPUT 200mA/div 50µs/div ILOAD = 1mA, INPUT = 3.3V, CSS = 10nF, COUT = 2 x 0.68µF 100µs/div ILOAD = 1mA, INPUT = 3.3V, CSS = 10nF, COUT = 4.7µF _______________________________________________________________________________________ 5 MAX606/MAX607 Typical Operating Characteristics (continued) (VIN = 3.3V, TA = +25°C, unless otherwise noted.) MAX606/MAX607 Low-Profile, 5V/12V or Adjustable, Step-Up DC-DC Converters for Flash Memory/PCMCIA Cards Typical Operating Characteristics (continued) (VIN = 3.3V, TA = +25°C, unless otherwise noted.) MAX607 LOAD-TRANSIENT RESPONSE MAX606 LOAD-TRANSIENT RESPONSE OUTPUT 50mV/div OUTPUT 50mV/div 60mA 60mA OUTPUT 20mA/div OUTPUT 20mA/div 10µs/div 20µs/div ILOAD = 5mA to 60mA, OUTPUT = 12V, INPUT = 3.3V ILOAD = 5mA to 60mA, OUTPUT = 12V, INPUT = 3.3V MAX607 LINE-TRANSIENT RESPONSE MAX606 LINE-TRANSIENT RESPONSE OUTPUT 100mV/div OUTPUT 100mV/div 4V INPUT 500mV/div 3V 50µs/div ILOAD = 10mA, OUTPUT = 12V, INPUT = 3.3V TO 4.3V 6 4V INPUT 500mV/div 3V 100µs/div ILOAD = 10mA, OUTPUT = 12V, INPUT = 3.3V TO 4.3V _______________________________________________________________________________________ Low-Profile, 5V/12V or Adjustable, Step-Up DC-DC Converters for Flash Memory/PCMCIA Cards PIN NAME FUNCTION 1 PGND 2 FB Feedback Input. Connect to IN for 5V output, to GND for 12V output, or to a resistive voltage divider between OUT and GND for an adjustable output between IN and 12.5V. 3 SHDN Shutdown Input, Active Low. Connect to GND to power down or to IN for normal operation. Output power FET is held off when SHDN is low. 4 IN 5 GND Analog Ground 6 SS Soft-Start Input 7 OUT 8 LX Power Ground. Source of n-channel power MOSFET. Supply Voltage Input: 3.0V to 5.5V Output. Always connect directly to the circuit output. Drain of n-channel power MOSFET +5V INPUT +3.3V INPUT C2 C1 C1 C2 L1 IN ON/OFF C4 L1 D1 LX SHDN SS MAX606 OUTPUT 12V @ 120mA FB SHDN C3 MAX607 OUT FB GND ON/OFF PGND Figure 1. 12V Standard Application Circuit Standard Application Circuits This data sheet provides two predesigned standard application circuits. The circuit of Figure 1 produces 12V at 120mA from a 5V input. Table 1 lists component values and part numbers for both the MAX606 and MAX607 variations of this circuit. The circuit of Figure 2 produces IN D1 LX MAX606 C4 OUTPUT 5V @ 180mA C3 SS MAX607 OUT GND PGND Figure 2. 5V Standard Application Circuit 5V at a typical output current of 180mA from a 3.3V input. Each application circuit is designed to deliver the full rated output load current over the temperature range listed. Component values and part numbers for this circuit are listed in Table 2. See Table 3 for component suppliers’ phone and fax numbers. _______________________________________________________________________________________ 7 MAX606/MAX607 Pin Description MAX606/MAX607 Low-Profile, 5V/12V or Adjustable, Step-Up DC-DC Converters for Flash Memory/PCMCIA Cards Table 1. Suggested Components for 12V Standard Application Circuit of Figure 2 DESIGNATION MAX606 MAX607 DESIGNATION MAX606 MAX607 L1 5µH inductor Dale ILS-3825-XX 10µH inductor Sumida CLS62-100 L1 5µH, 1A inductor Dale ILS-3825-XX 10µH, 0.7A inductor Sumida CLS62B-100 D1 0.5A, 20V diode Motorola MBR0520L 0.5A, 20V diode Motorola MBR0520L D1 0.5A, 20V diode Motorola MBR0520L 0.5A, 20V diode Motorola MBR0520L C1 0.1µF ceramic cap. 0.1µF ceramic cap. C1 0.1µF ceramic cap. 0.1µF ceramic cap. C2 2 x 0.68µF ceramic cap. 2.2µF ceramic cap. Marcon Marcon THCR20E1E684Z THCR30E1E225M C2 2 x 0.68µF ceramic cap. 2.2µF ceramic cap. Marcon Marcon THCR20E1E684Z THCR30E1E225M C3 2 x 0.68µF ceramic cap. 2 x 1µF ceramic cap. Marcon Marcon THCR20E1E684Z THCR30E1E105M C3 4.7µF ceramic cap. Marcon THCR30E1E475M 4.7µF ceramic cap. Marcon THCR30E1E475M C4 10nF ceramic cap. C4 10nF ceramic cap. 10nF ceramic cap. 10nF ceramic cap. Detailed Description The remainder of this document contains the detailed information you’ll need to design a circuit that differs from the two Standard Application Circuits. If you are using one of the predesigned circuits, the following sections are purely informational. The MAX606/MAX607 CMOS, step-up DC-DC converters employ a current-limited pulse-frequency control scheme. This control scheme regulates a boost topology to convert input voltages between 3V and 5.5V into either a pin-programmable 5V/12V output, or an adjustable output between VIN and 12.5V. It optimizes performance over all input and output voltages, and guarantees output accuracy to ±4%. The ultra-high switching frequency (typically 1MHz for the MAX606 and 0.5MHz for the MAX607) permits the use of extremely small external components, making these converters ideal for use in Types 1, 2, and 3 flash memory and PCMCIA applications. Pulse-Frequency-Modulation Control Scheme The MAX606/MAX607 employ a proprietary, currentlimited control scheme that combines the ultra-low supply current of traditional pulse-skipping converters with the high full-load efficiency of current-mode pulsewidth-modulation converters. This particular control scheme is similar to the one used in previous currentlimited devices (which governed the switching current 8 Table 2. Suggested Components for 5V Standard Application Circuit of Figure 1 Table 3. Component Suppliers SUPPLIER PHONE FAX Dale Inductors 605-668-4131 605-665-1627 Marcon/United Chemi-Con 708-696-2000 708-518-9985 Motorola 602-244-3576 602-244-4015 Sumida USA 708-956-0666 708-956-0702 03-607-5111 03-607-5144 Sumida Japan via maximum on-time, minimum off-time, and current limit), except it varies the on and off times according to the input and output voltages. This important feature enables the MAX606/MAX607 to achieve ultra-high switching frequencies while maintaining high output accuracy, low output ripple, and high efficiency over a wide range of loads and input/output voltages. Figure 3 shows the functional diagram of the MAX606/ MAX607. The internal power MOSFET is turned on when the error comparator senses that the output is out of regulation. The power switch stays on until either the timing circuit turns it off at the end of the on-time, or the switch current reaches the current limit. Once off, the switch remains off during the off-time. Subsequently, if the output is still out of regulation, another switching cycle is initiated. Otherwise, the switch remains turned off as long as the output is in regulation. _______________________________________________________________________________________ Low-Profile, 5V/12V or Adjustable, Step-Up DC-DC Converters for Flash Memory/PCMCIA Cards MAX606/MAX607 IN TIMING CIRCUIT tOFF tON EN ON INH UNDERVOLTAGE LOCKOUT CONTROL LOGIC LX CURRENT-LIMIT COMPARATOR OFF INTERNAL POWER 1Ω SWITCH DRIVER RLIM PGND SS OUT VREF MAX606 MAX607 REF SHDN ERROR COMPARATOR INT/EXT FB FB DUAL MODE 5V/12V Figure 3. Functional Diagram The on/off times are determined by the input and output voltages: tON = K / VIN tOFF = 0.5 · K / (VOUT + VDIODE - VIN) K is typically 3µs-V for the MAX606 and 6µs-V for the MAX607. This factor is chosen to set the optimum switching frequency and the one-cycle current limit, which determines the no-load output ripple at low output-to-input voltage differentials. The factor of 0.5 in the off-time equation is the typical switch off-time ratio. This ratio guarantees high efficiency under a heavy load by allowing the inductor to operate in continuous-conduction mode. For example, a switch off-time ratio of 1 would cause the device to operate on the edge of discontinuous-conduction mode. To determine the actual switch off-time ratio for a particular device, measure tON, tOFF, VIN, and VOUT, and then solve for the ratio by substituting these values into the off-time equation. Unlike PWM converters, the MAX606/MAX607 generate variable-frequency switching noise. However, the amplitude of this noise does not exceed the product of the switch current limit and the output capacitor equivalent series resistance (ESR). Traditional clocked-PFM or pulse-skipping converters cannot make this claim. Output Voltage Selection The MAX606/MAX607 output voltage is pin-programmable to 5V and 12V, and also adjustable to voltages between VIN and 12.5V. Connect FB to IN for a 5V output, to GND for a 12V output, or to a resistive divider between the output and GND for an adjustable output. Always connect OUT to the output. _______________________________________________________________________________________ 9 MAX606/MAX607 Low-Profile, 5V/12V or Adjustable, Step-Up DC-DC Converters for Flash Memory/PCMCIA Cards INPUT IN LX OUTPUT 10pF MAX606 MAX607 OUT R1 FB GND PGND Undervoltage Lockout R2 VOUT = VREF VREF = 2V ( R1 +1 R2 ) Figure 4. Adjustable Output Voltage When FB is connected to IN or GND, an internal voltage divider is configured to produce a predetermined output. However, when the voltage at FB is between 0.1V above ground and 0.1V below VIN, the device is in the adjustable output mode. In this mode, the MAX606/MAX607 output voltage is set by two external resistors, R1 and R2 (Figure 4), which form a voltage divider between the output and FB. Use the following equation to determine the output voltage: VOUT = VREF (R1 / R2 + 1) where VREF = 2V. To simplify the resistor selection: R1 = R2 [(VOUT / VREF) - 1] Since the input current at FB is 200nA maximum, large values (up to 100kΩ) can be used for R2 with no significant loss of accuracy. For 1% error, the current through R2 should be at least 100 times the FB input bias current. Soft-Start Connecting a capacitor to the Soft-Start (SS) pin ensures a gradually increasing current limit during power-up or when exiting shutdown, thereby reducing initial inrush currents. This feature can be useful, for example, when an old battery’s increased series resistance limits initial inrush currents. Using the soft-start feature in a situation like this minimizes the risk of overloading the incoming supply. Soft-start timing is controlled by the value of the SS capacitor. On power-up, the SS capacitor is charged by the 2V reference through an internal, 45kΩ pull-up resistor. As the voltage on the SS pin increases, the voltage at the SS clamp output also increases, which in turn raises the current-limit threshold. The Start-Up Delay vs. 10 SS Capacitor graph in the Typical Operating Characteristics shows typical timing characteristics for selected capacitor values and circuit conditions. The soft-start capacitor is discharged each time the MAX606 or MAX607 is put into shutdown, including during undervoltage lockout and when powering down at IN. If the circuit is required to start up with no load, as in flash memory programming supplies, soft-start is not required. Omitting the soft-start capacitor permits a minimum output voltage rise time from the shutdown state, improving flash memory access time. The MAX606/MAX607 monitor the supply voltage at IN and operate for supply voltages greater than 2.8V. When an undervoltage condition is detected, control logic turns off the output power FET and discharges the soft-start capacitor to ground. The control logic holds the output power FET in an off state until the supply voltage rises above the undervoltage threshold, at which time a soft-start cycle begins. Shutdown Mode Connecting SHDN to GND will hold the MAX606/ MAX607 in shutdown mode. In shutdown, the output power FET is off, but there is still an external path from IN to the load via the inductor and diode. The internal reference also turns off, which causes the soft-start capacitor to discharge. Typical device standby current in shutdown mode is 0.01µA. For normal operation, connect SHDN to IN. A soft-start cycle is initiated when the MAX606/MAX607 exit shutdown. Applications Information Inductor Selection Use a 5µH inductor for the MAX606 and a 10µH inductor for the MAX607. See Table 3 for a list of component suppliers. Higher inductor values allow greater load currents due to operation in continuous-conduction mode, while lower inductor values lead to smaller physical size due to lower energy-storage requirements and lower output-filter-capacitor requirements. Potential drawbacks of using lower inductor values are increased output ripple, lower efficiency, and lower output-current capability due to operation in discontinuous-conduction mode. (See the Maximum Output Current vs. Inductor Value graph in the Typical Operating Characteristics.) The inductor must have a saturation (incremental) current rating equal to the peak switch-current limit, which is 1.1A. For highest efficiency, minimize the inductor’s DC resistance. ______________________________________________________________________________________ Low-Profile, 5V/12V or Adjustable, Step-Up DC-DC Converters for Flash Memory/PCMCIA Cards Capacitor Selection Output Filter Capacitor The output voltage ripple is a function of the output capacitor’s equivalent series resistance (ESR) and capacitance. For best performance, use ceramic capacitors. Higher-ESR capacitors, such as tantalums, will cause excessive ripple. See Table 3 for a list of component suppliers. The output voltage ripple is approximately 100mVp-p for the 12V Standard Application Circuit (Figure 1) and 50mV for the 5V circuit (Figure 2). To further reduce this ripple, or to reduce the ripple on a different application circuit, increase the value of the output filter capacitor. If this capacitor is low ESR (e.g., ceramic), the output voltage ripple will be dominated by this capacitance. Input Bypass Capacitors For applications where the MAX606/MAX607 are physically close to the input supply’s filter capacitor (e.g., in PCMCIA drivers from the host computer), the input bypass capacitor may not be necessary. ___________________Chip Topography PGND LX PGND LX PGND LX 0.084" (2.134mm) SEL OUT SHDN SS V+ GND 0.058" (1.473mm) TRANSISTOR COUNT: 613 SUBSTRATE CONNECTED TO GND In other applications where the MAX606/MAX607 are more than a few inches away from the supply (such as memory cards), the input bypass capacitor is needed to reduce reflected current ripple to the supply and improve efficiency by creating a low-impedance path for the ripple current. Under these circumstances, the associated high Q and low ESR of ceramic capacitors do not diminish the problem. Therefore, include some low-Q, moderate-ESR capacitance (e.g., tantalum) at the input in order to reduce ringing. Layout The MAX606/MAX607’s high-frequency operation and high peak currents make PC board layout critical to minimize ground bounce and noise. Locate input bypass and output filter capacitors as close to the device pins as possible. All connections to OUT (and to FB when operating in adjustable-output mode) should also be kept as short as possible. A ground plane is recommended. Solder GND and PGND directly to the ground plane. Refer to the MAX606/MAX607 evaluation kit manual for a suggested surface-mount layout. ______________________________________________________________________________________ 11 MAX606/MAX607 Diode Selection The MAX606/MAX607’s high switching frequency demands a high-speed rectifier. Use a Schottky diode with at least a 0.5A average current rating and a 1.2A peak current rating, such as an MBR0520L. See Table 3 for a list of component suppliers. ________________________________________________________Package Information 8LUMAXD.EPS MAX606/MAX607 Low-Profile, 5V/12V or Adjustable, Step-Up DC-DC Converters for Flash Memory/PCMCIA Cards 12 ______________________________________________________________________________________