19-1219; Rev 1; 6/97 ANUAL N KIT M IO T A U EVAL BLE AVAILA 28V, Low-Power, High-Voltage, Boost or Inverting DC-DC Converter The MAX629’s combination of low supply current, logiccontrolled shutdown, small package, and tiny external components makes it an extremely compact and efficient high-voltage biasing solution that’s ideal for battery-powered applications. The MAX629 is available in an 8-pin SO package. ________________________Applications ____________________________Features ♦ Internal, 500mA, 28V N-Channel Switch (No External FET Required) ♦ Generates Positive or Negative Output Voltages ♦ 80µA Supply Current ♦ 1µA Max Shutdown Current ♦ Up to 300kHz Switching Frequency ♦ Adjustable Current Limit Allows Use of Small, Inexpensive Inductors ♦ 8-Pin SO Package ______________Ordering Information PART TEMP. RANGE PIN-PACKAGE MAX629C/D 0°C to +70°C Dice* MAX629ESA -40°C to +85°C 8 SO *Dice are tested at TA = +25°C, DC parameters only. Note: To order tape-and-reel shipping, add “-T” to the end of the part number. Positive or Negative LCD Bias Generators High-Efficiency DC-DC Boost Converters Varactor Tuning Diode Bias Palmtop Computers Pin Configuration appears at end of data sheet. 2-Cell and 3-Cell Battery-Powered Applications ___________________________________________________Typical Operating Circuit VIN +2.7V TO +5.5V VIN +2.7V TO +5.5V VCC SHDN LX VOUT 28V VCC SHDN LX ISET -VOUT -28V ISET FB POL MAX629 POL MAX629 REF FB REF GND GND POSITIVE OUTPUT VOLTAGE NEGATIVE OUTPUT VOLTAGE ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800 MAX629 _______________General Description The MAX629 low-power DC-DC converter features an internal N-channel MOSFET switch and programmable current limiting. It is designed to supply positive or negative bias voltages up to ±28V from input voltages in the 0.8V to VOUT range, and can be configured for boost, flyback, and SEPIC topologies. The MAX629’s current-limited pulse-frequency-modulation (PFM) control scheme provides high efficiency over a wide range of load conditions. An internal, 0.5A Nchannel MOSFET switch reduces the total part count, and a high switching frequency (up to 300kHz) allows for tiny surface-mount magnetics. MAX629 28V, Low-Power, High-Voltage, Boost or Inverting DC-DC Converter ABSOLUTE MAXIMUM RATINGS Supply Voltage (VCC to GND) ..................................-0.3V to +6V SHDN to GND...........................................................-0.3V to +6V ISET, REF, FB, POL to GND .......................-0.3V to (VCC + 0.3V) LX to GND ..............................................................-0.3V to +30V Continuous Power Dissipation (TA = +70°C) SO (derate 5.88mW/°C above +70°C) ..........................471mW Operating Temperature Range ...........................-40°C to +85°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +165°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 (VCC = +5V, CREF = 0.1µF, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note1) PARAMETER CONDITIONS VCC Input Voltage (Note 2) MIN VFB = 1.3V VCC Shutdown Current SHDN = GND VCC Undervoltage Lockout 100mV hysteresis 2.3 Input Supply Voltage (Note 2) Voltage applied to L1 (VIN) 0.8 VIH 2.4 Circuit of Figure 2 Negative Output Voltage Circuit of Figure 3 LX On-Resistance LX Leakage Current µA 0.04 1 µA 2.5 2.65 V VOUT V V 28 V V 0.45 0.25 0.33 VCC = 5V 0.6 1.2 VCC = 3.3V 0.7 1.4 VLX = 28V, TA = +85°C 0.05 2.5 µA µs ISET = VCC ISET = GND 0.20 6.5 8.5 10.0 POL = GND 0.7 1.0 1.3 POL = VCC 2.0 3.2 3.8 POL = GND, VFB < 1V 3.0 4.5 6.0 POL = VCC, VFB > 0.25V 3.0 4.5 6.0 1.250 1.275 POL = GND (positive output) TA = 0°C to +85°C 1.225 TA = -40°C to +85°C 1.218 POL = VCC (negative output) TA = 0°C to +85°C -15 TA = -40°C to +85°C -25 FB Input Bias Current 2 UNITS -28 0.51 -VIN 0.39 FB Set Point REF Output Voltage V 120 0.4 Maximum LX On-Time Minimum LX Off-Time 5.5 80 VIL Positive Output Voltage LX Switch-Current Limit MAX 2.7 VCC Supply Current SHDN, POL, ISET Logic Levels TYP VCC = 2.7V to 5.5V, no load on REF TA = 0°C to +85°C 1.225 TA = -40°C to +85°C 1.218 1.282 0 15 25 5 50 1.250 1.275 _______________________________________________________________________________________ 1.282 A Ω µs V mV nA V 28V, Low-Power, High-Voltage, Boost or Inverting DC-DC Converter MAX629 ELECTRICAL CHARACTERISTICS (continued) (VCC = +5V, CREF = 0.1µF, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) TYP MAX UNITS REF Load Regulation PARAMETER IREF = 0µA to 100µA, CREF = 0.47µF (Note 3) CONDITIONS MIN 10 25 mV Line Regulation Circuit of Figure 2, VOUT = 24V, VCC = 3V to 5.5V, ILOAD = 5mA 0.2 %/V Load Regulation Circuit of Figure 2, VOUT = 24V, VCC = 5V, ILOAD = 0mA to 5mA 0.15 % Thermal Shutdown Threshold Die temperature 150 °C Note 1: Specifications to -40°C are guaranteed by design and not production tested. Note 2: The IC itself requires a supply voltage between +2.7V and +5.5V; however, the voltage that supplies power to the inductor can vary from 0.8V to 28V, depending on circuit operating conditions. Note 3: For reference currents less than 10µA, a 0.1µF reference-bypass capacitor is adequate. __________________________________________Typical Operating Characteristics (SHDN = VCC , CREF = 0.1µF, TA = +25°C, unless otherwise noted.) 80 D 75 E, F C 80 75 VOUT = 12V, ISET = VCC or GND A: VIN = 9V B: VIN = 5V C: VIN = 3V 70 D: VIN = 5V, ISET = GND E: VIN = 3V, ISET = VCC F: VIN = 3V, ISET = GND 65 1 100 10 0.1 EFFICIENCY vs. LOAD CURRENT (VOUT = -12V) 95 85 A 80 B C 75 D 70 55 80 A B, C D 75 70 65 A: VIN = 12V, ISET = VCC B: VIN = 12V, ISET = GND C: VIN = 5V, ISET = VCC or GND D: VIN = 3V, ISET = VCC or GND 60 EFFICIENCY (%) 90 A = VIN = 5V, ISET = VCC B = VIN = 5V, ISET = GND C = VIN = 3V, ISET = VCC D = VIN = 3V, ISET = GND 60 55 50 1 10 LOAD CURRENT (mA) 100 100 D 50 0.1 1 10 LOAD CURRENT (mA) 0 4 8 12 16 90 A 80 20 70 B 60 A: VOUT = -12V, ISET = VCC B: VOUT = -18V, ISET = VCC C: VOUT = -12V, ISET = GND D: VOUT = -18V, ISET = GND 50 40 30 C 20 D 10 0 50 0.1 C B MAXIMUM LOAD CURRENT vs. INPUT VOLTAGE (VOUT = -18V, -12V) MAX629-05 MAX629-04 100 85 150 A INPUT VOLTAGE (V) EFFICIENCY vs. LOAD CURRENT (VOUT = -18V) 90 200 100 10 LOAD CURRENT (mA) 95 65 1 LOAD CURRENT (mA) 100 250 0 60 0.1 MAXIMUM LOAD CURRENT (mA) 60 EFFICIENCY (%) B 85 A: VOUT = 12V, ISET = VCC B: VOUT = 12V, ISET = GND C: VOUT =24V, ISET = VCC D: VOUT = 24V, ISET = GND MAX629-06 C 65 MAXIMUM LOAD CURRENT (mA) 90 EFFICIENCY (%) EFFICIENCY (%) 85 70 95 A A B 300 MAX629-02 VOUT = 24V A: VIN = 12V, ISET = VCC B: VIN = 12V, ISET = GND C: VIN = 5V, ISET = VCC 90 100 MAX629-01 100 95 MAXIMUM LOAD CURRENT vs. INPUT VOLTAGE (VOUT = +24V, +12V) EFFICIENCY vs. LOAD CURRENT (VOUT = +12V) MAX629-03 EFFICIENCY vs. LOAD CURRENT (VOUT = +24V) 100 0 4 8 12 16 20 INPUT VOLTAGE (V) _______________________________________________________________________________________ 3 ____________________________Typical Operating Characteristics (continued) (SHDN = VCC , CREF = 0.1µF, TA = +25°C, unless otherwise noted.) SUPPLY CURRENT vs. INPUT VOLTAGE REFERENCE VOLTAGE vs. REFERENCE LOAD CURRENT VIN = VCC 500 VIN = VCC = 5V C4 = 0.47µF REFERENCE VOLTAGE (V) 600 IIN 400 IIN 300 200 ICC 100 MAX629-08 1.255 MAX629-07 700 1.250 1.245 1.240 1.235 0 1.230 0 1 2 3 4 5 0 20 INPUT VOLTAGE (V) 60 40 MAX629-10 MAX629-09 100 120 140 160 LOAD-TRANSIENT RESPONSE (ISET = GND, ILIM = 250mA) LOAD-TRANSIENT RESPONSE (ISET = VCC, ILIM = 500mA) OUTPUT VOLTAGE RIPPLE A 80 REFERENCE LOAD CURRENT (µA) 0mA MAX629-11 SUPPLY CURRENT (µA) 0mA A A 5mA 5mA B B B 100µs/div 200µs/div 10µs/div VOUT = +24V, ISET = VCC A: LOAD CURRENT, 0mA TO 5mA, 2.5mA/div B: VOUT, AC-COUPLED, 10mV/div SHUTDOWN TRANSIENT (POSITIVE CONFIGURATION) 5V SHUTDOWN TRANSIENT (NEGATIVE CONFIGURATION) 5V SHDN SHDN 0V 0V 24V VOUT = +24V, ISET = GND A: LOAD CURRENT, 0mA TO 5mA, 2.5mA/div B: VOUT, AC-COUPLED, 10mV/div MAX629-13 VOUT = +24V, ILOAD = 5mA A: ISET = VCC, 20mV/div B: ISET = GND, 20mV/div MAX629-12 MAX629 28V, Low-Power, High-Voltage, Boost or Inverting DC-DC Converter 0V VOUT VOUT 0V -20V 50ms/div VCC = VIN = 5V, RL = 4kΩ 4 20ms/div 50ms/div START-UP VCC = VIN =DELAY, 5V, RL =VCC 4kΩ = VIN = 5V, ILOAD = 5mA _______________________________________________________________________________________ 28V, Low-Power, High-Voltage, Boost or Inverting DC-DC Converter PIN NAME FUNCTION 1 SHDN Active-Low Shutdown Input. A logic low puts the MAX629 in shutdown mode and reduces supply current to 1µA. 2 POL Polarity Input. Changes polarity and threshold of FB to allow regulation of either positive or negative output voltages. Set POL = GND for positive output voltage, or set POL = VCC for negative output voltage. 3 REF 1.25V Reference Output. Bypass to GND with a 0.1µF capacitor for IREF ≤ 10µA. REF can source 100µA to drive external loads. For 10µA ≤ IREF ≤ 100µA, bypass REF with a 0.47µF capacitor. 4 FB Feedback Input for setting output voltage. Connect to an external voltage divider. See Setting the Output Voltage. 5 ISET Current-Limit Set Input. Connect to VCC for a 500mA LX current limit, or connect to GND for a 250mA LX current limit. See Setting the Current Limit. 6 GND Ground 7 LX 8 VCC Internal N-Channel DMOS Switch Drain Power-Supply Input _______________Detailed Description The MAX629 low-power, boost DC-DC converter provides either positive or negative output voltages up to ±28V from a wide range of input voltages. It is designed primarily for use in low-power, high-voltage applications such as LCD biasing and set-top box varactor tuning. The MAX629’s unique control scheme provides high efficiency and a wide range of output voltages with only 80µA quiescent supply current, making it ideal for battery-powered applications. The internal N-channel DMOS switch has a pin-programmable current limit (250mA and 500mA), allowing optimization of output current and component size. Figure 1 shows the MAX629 functional diagram. Control Scheme A combination of peak-current limiting and a pair of one-shots controls the MAX629 switching, determining the maximum on-time and constant off-time. During the on-cycle, the internal switch closes, and current through the inductor ramps up until either the fixed 10µs maximum on-time expires (at low input voltages) or the switch’s peak current limit is reached. The peak switch current limit is selectable to either 500mA (ISET = V CC ) or 250mA (ISET = GND) (see Setting the Current Limit). After the on-cycle terminates, the switch turns off, charging the output capacitor through the diode. In normal operation, the minimum off-time is set to 1µs for positive output voltages and 3.5µs for negative output voltages. When the output is well below reg- ulation, however, the off-time is increased to 5µs to provide soft-start during start-up. The switching frequency, which depends upon the load, can be as high as 300kHz. Shutdown Mode When SHDN is low, the MAX629 enters shutdown mode. In this mode, the feedback and control circuit, reference, and internal biasing circuitry turn off. The shutdown current drops to less than 1µA. SHDN is a logic-level input; connect it to VCC for normal operation. The output voltage behavior in shutdown mode depends on the output voltage polarity. In the positive output voltage configuration (Figure 2), the output is directly connected to the input through the diode (D1) and the inductor (L1). When the device is in shutdown mode, the output voltage falls to one diode drop below the input voltage, and any load connected to the output may still conduct current. In the negative output voltage configuration (Figure 3), there is no DC connection between the input and the output, and in shutdown mode the output is pulled to GND. __________________Design Procedure Setting the Output Voltage For either positive or negative output voltage applications, set the MAX629’s output voltage using two external resistors, R1 and R2, as shown in Figures 2 and 3. Since the input bias current at FB has a 50nA maximum value, large resistors can be used in the feedback loop _______________________________________________________________________________________ 5 MAX629 ______________________________________________________________Pin Description MAX629 28V, Low-Power, High-Voltage, Boost or Inverting DC-DC Converter POL REF MIN OFF-TIME GENERATOR TRIG POLARITY 1.25V REF START-UP MAX629 Q ERROR AMP LX F/F S FB Q R START-UP COMPARATOR ISET TRIG 1V MAX ON-TIME GENERATOR (10µs) Q SHDN CONTROL VCC GND Figure 1. Functional Diagram without a significant loss of accuracy. Begin by selecting R2 to be in the 10kΩ to 200kΩ range, and calculate R1 using the applicable equation from the following subsections. Positive Output Voltages For positive output voltages, use the typical boost configuration shown in Figure 2, connecting POL to GND. This sets the threshold voltage at FB to equal VREF. Choose the value of R2 and calculate R1 as follows: V R1 = R2 x OUT − 1 VREF where VREF = 1.25V. Negative Output Voltages For negative output voltages, configure R1 and R2 as shown in Figure 3, connecting POL to VCC. This sets 6 the FB threshold voltage to GND so that negative voltages can be regulated. Choose R2 and calculate R1 as follows: R1 = R2 x | VOUT | VREF where VREF = 1.25V. Figure 3 demonstrates generation of a negative output voltage by following the MAX629 with an inverting charge pump. This configuration limits VOUT to values between -VIN and -28V. If smaller negative output voltages are required, D2’s cathode can be connected to VIN. This alternative configuration permits output voltages smaller than -VIN, but cannot be used for output voltages more negative than -28V - VIN. It produces roughly one-half the output current as the standard configuration and is typically 5% less efficient. _______________________________________________________________________________________ 28V, Low-Power, High-Voltage, Boost or Inverting DC-DC Converter Inductor Selection The MAX629’s high switching frequency allows for the use of a small inductor. The 47µH inductor shown in the VIN +0.8V TO +15V VIN +0.8V TO +24V VCC +2.7V TO +5.5V VCC +2.7V TO +5.5V C1 10µF 35V * L1 47µH C3 0.1µF SHDN ISET MAX629 FB R2 31.6k 1% POL REF VOUT +24V LX R1 576k 1% C1 10µF 35V * L1 47µH C3 0.1µF D1 MBR0540L VCC C4 0.1µF Typical Operating Circuit is recommended for most applications. Larger inductances reduce the peak inductor current, but may limit output current capability at low input voltages and provide slower start-up times. Smaller inductances require less board space, but may cause greater peak current due to current-sense comparator propagation delay. If input voltages below 2V will be common, reducing the inductance to 22µH might improve performance; however, maximum load current and efficiency may decline. It is important to thoroughly test operation under all input and output conditions to ensure proper component selection. Inductors with a ferrite core or equivalent are recommended; powder iron cores are not recommended for use with high switching frequencies. The inductor’s incremental saturation rating must exceed the selected current limit. For highest efficiency, use an inductor with a low DC resistance (under 100mΩ). See Table 1 for a list of inductor suppliers. CF 150pF C2 10µF 35V C5 2.2µF VCC SHDN R3 2Ω D1 = D2 = MBR0540L LX POL R1 576k 1% MAX629 FB GND * FOR SINGLE-SUPPLY OPERATION Figure 2. +24V for a Positive LCD Bias CF 150pF C2 10µF 35V R2 35.7k 1% GND *FOR SINGLE-SUPPLY OPERATION VOUT -20V D1 D2 ISET REF C4 0.1µF * FOR SINGLE-SUPPLY OPERATION *FOR SINGLE-SUPPLY OPERATION Figure 3. -20V for a Negative LCD Bias _______________________________________________________________________________________ 7 MAX629 Setting the Current Limit External current-limit selection provides added control over the MAX629’s output performance. A higher current limit increases the amount of energy stored in the inductor during each cycle, which provides a higher output current capability. For higher output current applications, choose the 500mA current-limit option by connecting ISET to VCC. When lower output current is required, the 250mA current limit can provide several advantages. First, a smaller inductor can be used, which saves board area and cost. Second, the smaller energy transfer per cycle reduces output ripple for a given capacitor, providing design flexibility between board area, cost, and output ripple by allowing cheaper, higher-ESR capacitors. Connect ISET to GND to select the 250mA current-limit option. MAX629 28V, Low-Power, High-Voltage, Boost or Inverting DC-DC Converter Diode Selection The MAX629’s high switching frequency demands a high-speed rectifier. Schottky diodes, such as the 1N5819 or MBR0530L, are recommended. Make sure that the diode’s peak current rating exceeds the peak current set by ISET, and that its breakdown voltage exceeds the output voltage. Schottky diodes are preferred due to their low forward voltage. However, ultrahigh-speed silicon rectifiers are also acceptable. Table 1 lists Schottky diode suppliers. Capacitor Selection Output Filter Capacitor The primary criterion for selecting the output filter capacitor is low effective series resistance (ESR). The product of the peak inductor current and the output filter capacitor’s ESR determines the amplitude of the high-frequency ripple seen on the output voltage. These requirements can be balanced by appropriate selection of the current limit, as discussed in the Setting the Current Limit section. Table 1 lists some low-ESR capacitor suppliers. See the Output Voltage Ripple graph in the Typical Operating Characteristics section. Input Bypass Capacitor Although the output current of many MAX629 applications may be relatively small, the input must be designed to withstand current transients equal to the inductor current limit. The input bypass capacitor reduces the peak currents drawn from the voltage Table 1. Component Suppliers SUPPLIER PHONE FAX AVX: TPS series (803) 946-0690 (803) 626-3123 Matsuo: 267 series (714) 969-2491 (714) 960-6492 Sprague: 595D series (603) 224-1961 (603) 224-1430 Motorola: MBR0530L (602) 303-5454 (602) 994-6430 Nihon: EC11 FS1 series (805) 867-2555 (805) 867-2698 CAPACITORS DIODES INDUCTORS 8 source, and reduces noise caused by the MAX629’s switching action. The input source impedance determines the size of the capacitor required at the input (V IN). As with the output filter capacitor, a low-ESR capacitor is recommended. A 10µF, low-ESR capacitor is adequate for most applications, although smaller bypass capacitors may also be acceptable. Bypass the IC separately with a 0.1µF ceramic capacitor placed as close as possible to the VCC and GND pins. Reference Capacitor Bypass REF to GND with a 0.1µF ceramic capacitor for REF currents up to 10µA. REF can source up to 100µA of current for external loads. For 10µA ≤ IREF ≤ 100µA, bypass REF with a 0.47µF capacitor. Feed-Forward Capacitor Parallel a capacitor (CF) across R1 to compensate the feedback loop and ensure stability (Figures 2 and 3). Values up to 270pF are recommended for most applications. Choose the lowest capacitor value that ensures stability; high capacitance values may degrade line regulation. __________Applications Information Adjusting the Output Voltage Many biasing applications require an adjustable output voltage, which is easily obtained using the configuration in Figure 4. In this circuit, an external bias voltage (which may be generated by a potentiometer, a DAC, or other means) is coupled to FB through the resistor RB. The output voltage of this circuit is given by: VOUT = VINIT + R1 (V − VBIAS ) RB FB where VINIT is the fixed output voltage as calculated in the section Setting the Output Voltage, and VFB is equal to either VREF (1.25V) for the positive configuration or 0V for the negative configuration. Proper choice of RB provides a wide range of available output voltages using simple external components to generate VBIAS. Input Voltage Range Coilcraft: DO1608 and DT1608 series (847) 639-6400 (847) 639-1469 Murata-Erie: LQH4 series (814) 237-1431 (814) 238-0490 Sumida: CD43, CD54, and CDRH62B series (847) 956-0666 (847) 956-0702 TDK: NLC565050 series (847) 390-4373 (847) 390-4428 Although, in many cases, the MAX629 and the inductor are powered from the same source, it is often advantageous in battery-powered applications to power the device from an available regulated supply and to power the inductor directly from a battery. The MAX629 requires a +2.7V to +5.5V supply at VCC, but the inductor can be powered from as low as +0.8V, significantly _______________________________________________________________________________________ 28V, Low-Power, High-Voltage, Boost or Inverting DC-DC Converter R1 RB FB MAX629 VBIAS R2 GND (REF) ( ) ARE FOR NEGATIVE OUTPUT VOLTAGE CONFIGURATIONS. Figure 4. Adjustable Output Voltage increasing usable battery life. Using separate supplies for VCC and VIN also reduces noise injection onto VCC by isolating it from the switching transients, allowing a smaller, less-expensive input filter capacitor to be used in many applications. If input voltages below 2V will be common, reducing the inductor to 22µH may improve performance in this voltage range, at the potential cost of some decrease in maximum load current and efficiency. In the negative configuration shown in Figure 3, the inverting charge pump injects current into LX with each cycle. The amount of charge injected increases at higher VIN, and may prematurely trip the internal current- limit threshold. Resistor R3 increases the usable input voltage range by limiting the peak injected current. The 2Ω resistor shown provides a usable input voltage range beyond VIN = 15V. In applications with a different input voltage range, R3 may be increased or decreased as necessary, with a resulting efficiency change of roughly 0.5%/Ω. Layout Considerations Proper PC board layout is essential due to high current levels and fast switching waveforms that radiate noise. It is recommended that initial prototyping be performed using the MAX629 evaluation kit or equivalent PC board-based design. Breadboards or proto-boards should never be used when prototyping switching regulators. It is important to connect the GND pin, the input bypass-capacitor ground lead, and the output filtercapacitor ground lead to a single point (star ground configuration) to minimize ground noise and improve regulation. Also, minimize lead lengths to reduce stray capacitance, trace resistance, and radiated noise, with preference given to the feedback circuit, the ground circuit, and LX. Place R1 and R2 as close to the feedback pin as possible. Place the input bypass capacitor as close as possible to VCC and GND. Refer to the MAX629 evaluation kit data sheet for an example of proper board layout. _______________________________________________________________________________________ 9 MAX629 VOUT MAX629 28V, Low-Power, High-Voltage, Boost or Inverting DC-DC Converter __________________Pin Configuration ___________________Chip Information TRANSISTOR COUNT: 653 SUBSTRATE CONNECTED TO GND TOP VIEW SHDN 1 8 VCC 7 LX REF 3 6 GND FB 4 5 ISET POL 2 MAX629 SO 10 ______________________________________________________________________________________ 28V, Low-Power, High-Voltage, Boost or Inverting DC-DC Converter SOICN.EPS ______________________________________________________________________________________ 11 MAX629 ________________________________________________________Package Information 28V, Low-Power, High-Voltage, Boost or Inverting DC-DC Converter MAX629 NOTES 12 ______________________________________________________________________________________