19-2239; Rev 2; 3/09 KIT ATION EVALU E L B AVAILA 500kHz, 36V Output, SOT23, PWM Step-Up DC-DC Converters The MAX5025–MAX5028 constant-frequency, pulsewidth modulating (PWM), low-noise boost converters are intended for low-voltage systems that often need a locally generated high voltage. These devices are capable of generating low-noise, high output voltages required for varactor diode biasing in TV tuners, set-top boxes, and PCI cable modems. The MAX5025– MAX5028 operate from as low as 3V and switch at 500kHz. The constant-frequency, current-mode PWM architecture provides for low output noise that is easy to filter. A 40V lateral DMOS device is used as the internal power switch, making the devices ideal for boost converters up to 36V. The MAX5025/MAX5026 adjustable versions require the use of external feedback resistors to set the output voltage. The MAX5027/MAX5028 offer a fixed 30V output. These devices are available in a small, 6pin SOT23 package. Applications Features ♦ Input Voltage Range: 3V to 11V (MAX5026/MAX5028) 4.5V to 11V (MAX5025/MAX5027) ♦ Wide Output Voltage Range: VCC to 36V ♦ Output Power: 120mW (max) ♦ User-Adjustable Output Voltage with MAX5025/MAX5026 Using External Feedback Resistors ♦ Fixed 30V Output Voltage: MAX5027/MAX5028 ♦ Internal 1.3Ω (typ), 40V Switch ♦ Constant PWM Frequency Provides Easy Filtering in Low-Noise Applications ♦ 500kHz (typ) Switching Frequency ♦ 1μA (max) Shutdown Current ♦ Small, 6-Pin SOT23 Package TV Tuner Power Supply Low-Noise Varactor Diode Biasing Ordering Information Set-Top Box Tuner Power Supply PART PCI Cable Modem Voice-Over-Cable TEMP RANGE PIN-PACKAGE MAX5025EUT-T -40°C to +85°C 6 SOT23-6 MAX5026EUT-T -40°C to +85°C 6 SOT23-6 LCD Power Supply MAX5027EUT-T -40°C to +85°C 6 SOT23-6 Avalanche Photodiode Biasing MAX5028EUT-T -40°C to +85°C 6 SOT23-6 Typical Operating Circuit Selector Guide appears at end of data sheet. VCC = 4.5V TO 11V (MAX5027) VCC = 3V TO 11V (MAX5028) L1 D1 LX VCC TOP VIEW MAX5027 MAX5028 SHDN FB C1 Pin Configuration VOUT 30V C2 PGND 1 PGND GND 2 MAX5025– MAX5028 6 LX 5 VCC 4 SHDN GND FB 3 SOT23-6 ________________________________________________________________ Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. MAX5025–MAX5028 General Description MAX5025–MAX5028 500kHz, 36V Output, SOT23, Step-Up DC-DC Converters ABSOLUTE MAXIMUM RATINGS VCC to GND ............................................................-0.3V to +12V PGND to GND .......................................................-0.1V to +0.1V FB to GND (MAX5025/MAX5026)...............-0.3V to (VCC + 0.3V) FB to GND (MAX5027/MAX5028)...........................-0.3V to +40V SHDN to GND.............................................-0.3V to (VCC + 0.3V) LX to GND ..............................................................-0.3V to +45V Peak LX Current ................................................................600mA Operating Temperature Range ...........................-40°C to +85°C Continuous Power Dissipation (TA = +70°C) 6-Pin SOT23 (derate 8.7mW/°C above +70°C)..........695.7mW Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +165°C Lead Temperature (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 (VCC = 5V, SHDN = VCC, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS SUPPLY VOLTAGE Input Voltage Range Undervoltage Lockout Supply Current Shutdown Current VCC VUVLO ICC ISHDN MAX5026/MAX5028 3.0 11 MAX5025/MAX5027 4.5 11 Rise/fall, hysteresis = 3mV 2.25 V 2.65 2.95 V MAX5025/MAX5026, FB = 1.4V MAX5027/MAX5028, FB = 35V 350 1000 µA SHDN = GND 0.01 1 µA BOOST CONVERTER Switching Frequency fSW MAX5025/MAX5027 345 500 1000 MAX5026/MAX5028, VCC = 3.3V 410 500 670 MAX5025/MAX5027, ILOAD = 2mA, VCC = 4.5V to 11V, VOUT = 30V 0.25 Line Regulation %/V MAX5026/MAX5028, ILOAD = 0.5mA, VCC = 3V to 11V, VOUT = 30V 0.25 MAX5025/MAX5027, VCC = 5V, ILOAD = 0 to 4mA, VOUT = 30V 2.0 % Load Regulation MAX5026/MAX5028, VCC = 3.3V, ILOAD = 0 to 1mA, VOUT = 30V Thermal Shutdown Thermal Shutdown Hysteresis 2 kHz 1.0 140 °C 2 °C _______________________________________________________________________________________ 500kHz, 36V Output, SOT23, Step-Up DC-DC Converters MAX5025–MAX5028 ELECTRICAL CHARACTERISTICS (continued) (VCC = 5V, SHDN = VCC, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER FB Set Point SYMBOL VFB FB Input Bias Current IFB Output Voltage Adjustment Range CONDITIONS MIN TYP MAX MAX5025, VCC = 4.5V to 11V 1.19 1.25 1.31 MAX5027, VCC = 4.5V to 11V 28.5 30.0 31.5 MAX5026, VCC = 3.3V to 11V 1.212 1.25 1.288 MAX5028, VCC = 3.3V to 11V 29.0 UNITS V 30 31 MAX5025/MAX5026, FB = 1V 110 310 nA MAX5027/MAX5028, FB = 30V 100 170 µA 36 V VCC + 1 MAX5025/MAX5026 LX OUTPUT LX On-Resistance RON ILX = 40mA Switch Current Limit ILIM Note 2 MAX5026/MAX5028, VCC = 3V 2.0 4.0 VCC = 5V 1.3 3.0 1.0 2.5 VCC = 11V LX Leakage Current VLX = 40V 260 MAX5025/MAX5026, VFB = 1.4V 0.01 Ω mA 10 µA 0.8 V MAX5027/MAX5028, VFB = 35V LOGIC INPUT: SHDN Input Low Level VIL Input High Level VIH Input Bias Current 2.4 -1 V 1 µA Note 1: All devices are 100% production tested at TA = +25°C. All temperature limits are guaranteed by design. Note 2: Switch current-limit accuracy is typically ±20% and is a function of the input voltage. ILIM = (VIN/5) (260mA). _______________________________________________________________________________________ 3 Typical Operating Characteristics (VCC = 5V, VOUT = 30V, TA = +25°C, unless otherwise noted.) EFFICIENCY vs. LOAD CURRENT (VOUT = 12V) 40 MAX5026 VCC = 5V, VOUT = 12V CIRCUIT OF FIGURE 2. R1 = 147kΩ, R2 = 16.2kΩ 30 20 10 80 70 40 MAX5026 VCC = 5V, VOUT = 12V CIRCUIT OF FIGURE 2. R1 = 147kΩ, R2 = 13kΩ 30 10 60 2 4 6 8 10 MAX5026 VCC = 5V, VOUT = 24V CIRCUIT OF FIGURE 2. R1 = 147kΩ, R2 = 8.07kΩ 10 0 0 2 4 6 8 0 1 2 3 4 5 LOAD CURRENT (mA) EFFICIENCY vs. LOAD CURRENT (VOUT = 30V) MAX5026 MINIMUM STARTUP VOLTAGE vs. LOAD CURRENT MAX5026/MAX5028 SUPPLY CURRENT vs. SUPPLY VOLTAGE MAX5026 VCC = 5V, VOUT = 30V CIRCUIT OF FIGURE 2. R1 = 147kΩ, R2 = 6.34kΩ 10 2 3 2.5 2.0 1.5 400 350 300 250 200 150 100 0.5 50 0 0 0 4 MAX5025-28 toc06 450 1.0 0 1 3.0 500 SUPPLY CURRENT (μA) 30 20 3.5 STARTUP VOLTAGE (V) 40 MAX5025-28 toc05 4.0 MAX5025-28 toc04 50 1 2 3 4 CURRENT INTO VCC PIN DEVICE NOT SWITCHING 0 3 6 9 12 LOAD CURRENT (mA) SUPPLY VOLTAGE (V) MAX5026 NO LOAD SUPPLY CURRENT vs. SUPPLY VOLTAGE SUPPLY CURRENT vs. TEMPERATURE MAX5026 SWITCHING FREQUENCY vs. TEMPERATURE 8 6 4 VCC = 11V 750 VCC = 9V 650 VCC = 7V 550 VCC = 5V 450 VCC = 3V 350 250 2 CURRENT INTO VCC PIN 150 0 5 7 SUPPLY VOLTAGE (V) 9 11 650 VCC = 5V VOUT = 30V CIRCUIT OF FIGURE 2. 600 SWITCHING FREQUENCY (kHz) 10 MAX5025-28 toc08 12 850 SUPPLY CURRENT (μA) MAX5025-28 toc07 CIRCUIT OF FIGURE 2 VOUT = 30V 550 500 450 400 350 300 250 200 -40 -20 0 20 40 TEMPERATURE (°C) 60 80 -40 -20 0 20 40 TEMPERATURE (°C) _______________________________________________________________________________________ 60 80 MAX5025-28 toc09 LOAD CURRENT (mA) 16 3 30 LOAD CURRENT (mA) 60 14 40 LOAD CURRENT (mA) 70 0 50 20 0 0 EFFICIENCY (%) 50 20 0 4 60 70 EFFICIENCY (%) 50 80 MAX5025-28 toc03 90 EFFICIENCY (%) 60 EFFICIENCY vs. LOAD CURRENT (VOUT = 24V) MAX5025-28 toc02 70 EFFICIENCY (%) EFFICIENCY vs. LOAD CURRENT (VOUT = 15V) MAX5025-28 toc01 90 80 NO LOAD SUPPLY CURRENT (mA) MAX5025–MAX5028 500kHz, 36V Output, SOT23, Step-Up DC-DC Converters 500kHz, 36V Output, SOT23, Step-Up DC-DC Converters EXITING SHUTDOWN ENTERING SHUTDOWN MAX5025-28 toc10 OUTPUT VOLTAGE 20V/div MAX5025-28 toc11 30V 30V 5V INDUCTOR CURRENT 50mA/div 5V OUTPUT VOLTAGE 20V/div 5V SHUTDOWN VOLTAGE 5V/div 5V 0V SHUTDOWN VOLTAGE 5V/div 2ms/div 100ms/div MAX5026, VCC = 5V, VOUT = 30V, ILOAD = 1mA. CIRCUIT OF FIGURE 3 MAX5026, VCC = 5V, VOUT = 30V, ILOAD = 1mA. CIRCUIT OF FIGURE 3 LIGHT-LOAD SWITCHING WAVEFORM WITHOUT RC FILTER LIGHT-LOAD SWITCHING WAVEFORM WITH RC FILTER MAX5025-28 toc12 MAX5025-28 toc13 VOUT 2mV/div AC-COUPLED VOUT 1mV/div AC-COUPLED LX PIN 20V/div LX PIN 20V/div 0V IL 100mA/div 0mA 0V IL 100mA/div 1μs/div 0mA 1μs/div MAX5026, VCC = 5V, VOUT = 30V, ILOAD = 0.1mA. CIRCUIT OF FIGURE 2 MAX5026, VCC = 5V, VOUT = 30V, ILOAD = 0.1mA. CIRCUIT OF FIGURE 3 MEDIUM-LOAD SWITCHING WAVEFORM WITHOUT RC FILTER MEDIUM-LOAD SWITCHING WAVEFORM WITH RC FILTER MAX5025-28 toc15 MAX5025-28 toc14 VOUT 5mV/div AC-COUPLED VOUT 1mV/div AC-COUPLED LX PIN 20V/div LX PIN 20V/div 0V 0V IL 200mA/div 0mA 1μs/div MAX5026, VCC = 5V, VOUT = 30V, ILOAD = 2mA. CIRCUIT OF FIGURE 2 IL 200mA/div 0mA 1μs/div MAX5026, VCC = 5V, VOUT = 30V, ILOAD = 2mA. CIRCUIT OF FIGURE 3 _______________________________________________________________________________________ 5 MAX5025–MAX5028 Typical Operating Characteristics (continued) (VCC = 5V, VOUT = 30V, TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (VCC = 5V, VOUT = 30V, TA = +25°C, unless otherwise noted.) HEAVY-LOAD SWITCHING WAVEFORM WITHOUT RC FILTER HEAVY-LOAD SWITCHING WAVEFORM WITH RC FILTER MAX5025-28 toc16 MAX5025-28 toc17 VOUT 5mV/div AC-COUPLED VOUT 1mV/div AC-COUPLED LX PIN 20V/div LX PIN 20V/div 0V IL 200mA/div 0mA 0V IL 200mA/div 0mA 1μs/div 1μs/div MAX5026, VCC = 5V, VOUT = 30V, ILOAD = 4mA. CIRCUIT OF FIGURE 2 MAX5026, VCC = 5V, VOUT = 30V, ILOAD = 4mA. CIRCUIT OF FIGURE 3 LOAD TRANSIENT RESPONSE LINE TRANSIENT RESPONSE MAX5025-28 toc18 MAX5025-28 toc19 OUTPUT VOLTAGE 200mV/div AC-COUPLED OUTPUT VOLTAGE 1mV/div AC-COUPLED 0mV LOAD CURRENT 10mA/div 0mA 0mV INPUT VOLTAGE 100mV/div AC-COUPLED 0mV 1ms/div 2ms/div MAX5026, VCC = 5V, VOUT = 30V, ILOAD = 0 TO 4mA. CIRCUIT OF FIGURE 2 MAX5026, VCC = 5V TO 5.2V, VOUT = 30V, ILOAD = 1mA. CIRCUIT OF FIGURE 2 MAX5028 FB PIN VOLTAGE vs. TEMPERATURE MAX5025-28 toc20 1.270 1.265 VCC = 11V VCC = 5V 1.255 1.250 VCC = 3V 1.245 30.2 VCC = 11V 30.0 29.8 VCC = 5V 29.6 1.240 29.4 1.235 29.2 1.230 VCC = 3V 29.0 -40 6 30.4 FB PIN VOLTAGE (V) 1.260 MAX5025-28 toc21 MAX5026 FB PIN VOLTAGE vs. TEMPERATURE FB PIN VOLTAGE (V) MAX5025–MAX5028 500kHz, 36V Output, SOT23, Step-Up DC-DC Converters -20 0 20 40 TEMPERATURE (°C) 60 80 -40 -20 0 20 40 TEMPERATURE (°C) _______________________________________________________________________________________ 60 80 500kHz, 36V Output, SOT23, Step-Up DC-DC Converters SWITCH ON-RESISTANCE vs. TEMPERATURE LX LEAKAGE CURRENT vs. TEMPERATURE 2.5 2.0 VCC = 5V 1.5 0.040 0.035 0.030 0.025 0.020 0.015 0.010 1.0 0.005 VCC = 11V 0 0.5 0 20 40 60 0 20 40 60 TEMPERATURE (°C) LOAD REGULATION MAX5026 MAXIMUM LOAD CURRENT vs. INPUT VOLTAGE MAX5026 VCC = 5V WITHOUT RC FILTER (CIRCUIT OF FIGURE 2) 30 WITH RC FILTER (CIRCUIT OF FIGURE 3) 29 -20 TEMPERATURE (°C) 32 31 -40 80 28 80 100 MAXIMUM LOAD CURRENT (mA) -20 MAX5025-28 toc24 -40 OUTPUT VOLTAGE (V) CURRENT INTO LX PIN VLX = 40V 0.045 MAX5025-28 toc25 RON (Ω) VCC = 3V MAX5025-28 toc23 MAX5026 0.050 LX LEAKAGE CURRENT (μA) MAX5025-28 toc22 3.0 A B 10 C D E A: VOUT = 12V B: VOUT = 24V C: VOUT = 30V D: VOUT = 32V E: VOUT = 36V 1 0.1 0 1 2 3 LOAD CURRENT (mA) 4 5 3 5 7 9 11 INPUT VOLTAGE (V) _______________________________________________________________________________________ 7 MAX5025–MAX5028 Typical Operating Characteristics (continued) (VCC = 5V, VOUT = 30V, TA = +25°C, unless otherwise noted.) MAX5025–MAX5028 500kHz, 36V Output, SOT23, Step-Up DC-DC Converters Pin Description PIN MAX5025/ MAX5026 MAX5027/ MAX5028 NAME FUNCTION 1 1 PGND Power Ground. Connect directly to local ground plane. Use a star ground configuration for low noise. 2 2 GND Ground. Connect directly to local ground plane. 3 — FB Feedback Pin. Reference voltage is approximately 1.25V. Connect resistive-divider tap here. Minimize trace area at FB. See Setting the Output Voltage section. — 3 FB Feedback Pin. Connect VOUT to FB for +30V. Internal resistors divide down the output voltage. 4 4 SHDN 5 5 VCC 6 6 LX Shutdown Pin. Connect to VCC to enable device. Connect to GND to shut down. Input Supply Voltage. Bypass with a 4.7µF ceramic capacitor. Drain of Internal 40V N-Channel DMOS. Connect inductor/diode to LX. Minimize trace area at this pin to keep EMI down. Detailed Description The MAX5025–MAX5028 current-mode PWM controllers operate in a wide range of DC-DC conversion applications including boost, flyback, and isolated output configurations. These converters provide lownoise, high output voltages making them ideal for varactor diode tuning applications as well as TFT LCD bias. Other features include shutdown, fixed 500kHz PWM oscillator, and a wide input range: 3V to 11V for MAX5026/MAX5028 and 4.5V to 11V for MAX5025/ MAX5027. The MAX5025–MAX5028 operate in discontinuous mode in order to reduce the switching noise at the output. Other continuous mode boost converters generate a large voltage spike at the output when the LX switch turns on because there is a conduction path between the output, diode, and switch to ground during the time needed for the diode to turn off. To reduce the output noise even further, the LX switch turns off by taking 40ns typically to transition from “ON” to “OFF.” As a consequence, the positive slew rate of the LX node is reduced and the current from the inductor does not “force” the output voltage as hard as would be the case if the LX switch were to turn off more quickly. PWM Controller The heart of the MAX5025–MAX5028 current-mode PWM controllers is a BiCMOS multi-input comparator that simultaneously processes the output-error signal and switch current signal. The main PWM comparator 8 is direct summing, lacking a traditional error amplifier and its associated phase shift. The direct summing configuration approaches ideal cycle-by-cycle control over the output voltage since there is no conventional error amp in the feedback path. The device operates in PWM mode using a fixed-frequency, current-mode operation. The current-mode feedback loop regulates peak inductor current as a function of the output error signal. SHDN Input The SHDN pin provides shutdown control. Connect SHDN to V CC for normal operation. To disable the device, connect SHDN to GND. Design Procedure The MAX5025–MAX5028 can operate in a number of DC-DC converter configurations including step-up, single-ended primary inductance converter (SEPIC), and flyback. The following design discussions are limited to step-up, with a complete circuit shown in the Application Circuits section. Setting the Output Voltage The output voltage of the MAX5027/MAX5028 is fixed at 30V. The output voltage of the MAX5025/MAX5026 is set by two external resistors (R1 and R2, Figure 2 and Figure 3). First select the value of R2 in the 5kΩ to 50kΩ range. R1 is then given by: _______________________________________________________________________________________ 500kHz, 36V Output, SOT23, Step-Up DC-DC Converters ULVO 3 FB -A OSCILLATOR MAIN PWM COMPARATOR SHDN 4 LX 6 PGND 1 CONTROL LOGIC +A REF THERMAL SHUTDOWN +C 2 GND 5 VCC -C CURRENTLIMIT COMPARATOR N L = MAX5025 MAX5026 Figure 1. Functional Diagram Use the following formula to calculate the upper bound of the inductor value at different output voltages and output currents. This is the maximum inductance value for discontinuous mode operation. LUPPER = ⎛V ⎞ R1 = R2 ⎜ OUT - 1⎟ ⎝ VREF ⎠ where VREF is 1.25V Determining Peak Inductor Current If the boost converter remains in the discontinuous mode of operation, then the approximate peak inductor current, ILPEAK, is represented by the formula below: ILPEAK = 2 TS ( VOUT − VIN ) IOUT ηL where TS is the period, VOUT is the output voltage, VIN is the input voltage, IOUT is the output current, and η is the efficiency of the boost converter. (47μH) (VOUT − VIN ) (25V) 2 VIN (VOUT − VIN ) TSη 2 2 IOUT VOUT Calculate the lower bound, LLOWER, for the acceptable inductance value using the following formula, which will allow the maximum output current to be delivered without reaching the peak current limit: LLOWER = 2 TS ( VOUT − VIN ) IOUT ⎛V ⎞ η ⎜ IN (260mA)⎟ ⎝ 5 ⎠ 2 Notice that the switch current limit, (VIN/5)(260mA), is a function of the input voltage, VIN. The current rating of the inductor should be greater than the switch current limit. Table 1. Inductor Vendors VENDOR PHONE FAX PART NUMBER OF 47µH INDUCTOR Coilcraft 847-639-6400 847-639-1469 DT1608C-473 Sumida 847-545-6700 847-545-6720 CDRH4D28-470 Toko 847-297-0070 847-699-7864 A915BY-470M _______________________________________________________________________________________ 9 MAX5025–MAX5028 Determining the Inductor Value 47µH is the recommended inductor value when the output voltage is 30V and the input voltage is 5V. In general, the inductor should have a current rating greater than the current-limit value. For example, the inductor’s current rating should be greater than 150mA to support a 4mA output current. Equivalent series resistance (ESR) should be below 1Ω for reasonable efficiency. Due to the MAX5025–MAX5028’s high switching frequency, inductors with a ferrite core or equivalent are recommended. Powdered iron cores are not recommended due to their high losses at frequencies over 500kHz. Table 1 shows a list of vendors and 47µH inductor parts. For 4mA output current and output voltages other than 30V, the inductor can be simply scaled in value according to the following formula: MAX5025–MAX5028 500kHz, 36V Output, SOT23, Step-Up DC-DC Converters Capacitor Selection For a design in which VIN = 5V, VOUT = 30V, IOUT = 4mA, η = 0.5, and TS = 2µs, LUPPER = 87µH Output Filter Capacitor The output filter capacitor should be 1µF or greater. To achieve low output ripple, a capacitor with low ESR, low ESL, and high capacitance value should be selected. For very low output ripple applications, the output of the boost converter can be followed by an RC filter to further reduce the ripple. Figure 3 shows a 100Ω, 1µF filter used to reduce the switching output ripple to 1mVp-p. X7R ceramic capacitors are better for this boost application because of their low ESR and tighter tolerance over temperature than the Y5V ceramic capacitors. Table 3 below lists manufacturers of recommended capacitors. and LLOWER = 12µH. For a worst-case scenario in which VIN = 4.75V, VOUT = 29V, IOUT = 4.4mA, η = 0.5, and TS = 1.25µs, LUPPER = 46µH and LLOWER = 9µH. The choice of 47µH as the recommended inductance value is reasonable given the worst-case scenario above. In general, the higher the inductance, the lower the switching noise. Load regulation is also better with higher inductance. Input Capacitor Bypass VCC with a 4.7µF ceramic capacitor as close to the IC as is practical. Diode Selection The MAX5025–MAX5028’s high switching frequency demands a high-speed rectifier. Schottky diodes are recommended for most applications because of their fast recovery time and low forward-voltage drop. Ensure that the diode’s peak current rating is greater than or equal to the peak inductor current. Also, the diode reverse breakdown voltage must be greater than VOUT. Table 2 lists diode vendors. Applications Information Layout Considerations The MAX5025–MAX5028 switch at high speed, mandating careful attention to layout for optimum performance. Protect sensitive analog grounds by using a star ground configuration. Minimize ground noise by connecting GND, PGND, the input bypass-capacitor ground lead, and the output-filter ground lead to a single point (star ground configuration). Also, minimize Table 2. Schottky Diode Vendors VENDOR PHONE FAX PART NUMBERS Comchip 510-657-8671 510-657-8921 CDBS1045 Panasonic 408-942-2912 408-946-9063 MA2Z785 ST-Microelectronics 602-485-6100 602-486-6102 TMMBAT48 Vishay-Telefunken 402-563-6866 402-563-6296 BAS382 Zetex 631-360-2222 631-360-8222 ZHCS500 Table 3. Capacitor Table COMPANY PHONE FAX Murata 814-237-1431 814-238-0490 Taiyo Yuden 408-573-4150 408-573-4159 TDK 10 847-803-6100 847-803-6296 PART NUMBERS GRM42-2X7R105K050AD (1µF capacitor) GRM32-1210R71C475R (4.7µF capacitor) UMK325BJ105KH (1µF capacitor) EMK316BJ475ML (4.7µF capacitor) C3225X7R1H155K (1.5µF capacitor) C3225X7R1H105K (1µF capacitor) ______________________________________________________________________________________ 500kHz, 36V Output, SOT23, Step-Up DC-DC Converters Figures 2 and 3 show the MAX5025/MAX5026 operating in a 30V boost application. Figure 3 has an RC filter to reduce noise at the output. These circuits provide output currents greater than 4mA with an input voltage of 5V or greater. They are designed by following the Design Procedure section. Operating characteristics of these circuits are shown in the Typical Operating Characteristics section. Inductor Layout The shielded drum type inductors have a small air gap around the top and bottom periphery. The incident fringing magnetic field from this air gap to the copper plane on the PC board tends to reduce efficiency. This is a result of the induced eddy currents on the copper plane. To minimize this effect, avoid laying out any copper planes under the mounting area of these inductors. VCC = 4.5V TO 11V (MAX5025) VCC = 3V TO 11V (MAX5026) VCC C1 4.7μF L1 TOKO 47μH INDUCTOR 47μH A915BY-470M ZETEX SCHOTTKY DIODE D1 ZHCS500 VOUT LX +30V R1 147kΩ MAX5025 MAX5026 SHDN FB C2 1μF R2 6.34kΩ PGND GND Figure 2. Adjustable 30V Output Circuit VCC = 4.5V TO 11V (MAX5025) VCC = 3V TO 11V (MAX5026) VCC C1 4.7μF L1 TOKO 47μH INDUCTOR 47μH A915BY-470M ZETEX SCHOTTKY DIODE R3 100Ω D1 ZHCS500 LX MAX5025 MAX5026 SHDN FB PGND GND VOUT +30V R1 147kΩ C2 1μF C3 1μF R2 6.34kΩ Figure 3. Adjustable 30V Output Circuit with RC Filter ______________________________________________________________________________________ 11 MAX5025–MAX5028 30V Boost Application Circuit trace lengths to reduce stray capacitance, trace resistance, and radiated noise. The trace between the output voltage-divider (MAX5025/MAX5026) and the FB pin must be kept short, as well as the trace between GND and PGND. MAX5025–MAX5028 500kHz, 36V Output, SOT23, Step-Up DC-DC Converters Selector Guide PART OUTPUT FREQUENCY TOLERANCE FB SET POINT TOLERANCE INPUT VOLTAGE MAX5025 Adjustable -31% to +100% ±5% 4.5V to 11V MAX5026 Adjustable -18% to +34% ±3% 3V to 11V MAX5027 Fixed 30V -31% to +100% ±5% 4.5V to 11V MAX5028 Fixed 30V -18% to +34% ±3% 3V to 11V Package Information ____________________Chip Information TRANSISTOR COUNT: 365 PROCESS: BiCMOS 12 For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. PACKAGE TYPE PACKAGE CODE DOCUMENT NO. 6 SOT23 S8-2 21-0058 ______________________________________________________________________________________ 500kHz, 36V Output, SOT23, Step-Up DC-DC Converters REVISION NUMBER REVISION DATE DESCRIPTION PAGES CHANGED 0 10/01 Initial release — 1 12/01 Released the MAX5027 1 2 3/09 Revised the Absolute Maximum Ratings section. 2 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. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 13 © 2009 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc. MAX5025–MAX5028 Revision History