MAX828 MAX829 Switched Capacitor Voltage Converters The MAX828/829 are CMOS “charge–pump” voltage converters in ultra–small SOT–23 5 lead packages. They invert and/or double an input voltage which can range from +1.5V to +5.5V. Conversion efficiency is typically >95%. Switching frequency is 12kHz for the MAX828 and 35kHz for the MAX829. External component requirement is only two capacitors (3.3µF nominal) for standard voltage inverter applications. With a few additional components a positive doubler can also be built. All other circuitry, including control, oscillator, power MOSFETs are integrated on–chip. Supply current is 50 µA (MAX828) and 115 µA (MAX829). The MAX828 and MAX829 are available in a SOT–23 5 lead surface mount package. Features • • • • • • • • Charge Pump in SOT–23 5 Lead Package >95% Voltage Conversion Efficiency Voltage Inversion and/or Doubling Low 50 µA (MAX828) Quiescent Current Operates from +1.5V to +5.5V Up to 25 mA Output Current Only Two External Capacitors Required Tested Operating Temperature Range: –40°C to +85°C http://onsemi.com SOT–23–5 SN SUFFIX CASE TBD PRELIMINARY INFORMATION PIN CONFIGURATION (Top View) OUT 1 Vin 2 C– 3 Typical Applications • • • • • 4 GND SOT–23–5* LCD Panel Bias Cellular Phones Pagers PDAs, Portable Dataloggers Battery–Powered Devices NOTE: *SOT–23–5 is equivalent to EIAJ–SC74A ORDERING INFORMATION TYPICAL OPERATING CIRCUIT Device Voltage Inverter C+ Vin C– MAX828 MAX829 C1 Semiconductor Components Industries, LLC, 1999 Shipping MAX828SNTR SOT–23–5 3000 Tape/Reel MAX829SNTR SOT–23–5 3000 Tape/Reel V– OUTPUT OUT GND Package INPUT + February, 2000 – Rev. 0 5 C+ + C2 1 Publication Order Number: MAX828/D MAX828 MAX829 PIN DESCRIPTION ÁÁÁÁÁ ÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Pin No. Symbol Description 1 OUT Inverting charge pump output 2 VIN C– Positive power supply input 3 4 GND Ground 4 C+ Commutation capacitor negative terminal Commutation capacitor positive terminal ABSOLUTE MAXIMUM RATINGS* Symbol Value Unit Input Voltage (VIN to GND) Parameter +6.0, – 0.3 V Output Voltage (OUT to GND) –6.0, +0.3 V 50 mA Current at OUT Pin Short–Circuit Duration – OUT to GND TA Operating Temperature Range PD Power Dissipation (TA ≤ 70°C) SOT–23–5 Derate by 4mW/°C for TA > 70°C Tstg Storage Temperature Range Tsol Lead Temperature (Soldering, 10 Seconds) Indefinite –40 to +85 °C 240 mW –65 to +150 °C +300 °C * Maximum Ratings are those values beyond which damage to the device may occur. ELECTRICAL CHARACTERISTICS (TA = 0°C to +85°C, VIN = +5V, C1 = C2 = 10µF (MAX828), C1 = C2 = 3.3µF (MAX829), unless otherwise noted. Typical values are at TA = 25°C.) Symbol Min Typ Max Supply Current (TA = 25°C) MAX828 MAX829 — — 50 115 90 260 V+ Supply Voltage Range (RLOAD = 10kW) — — 5.5 FOSC Oscillator Frequency (TA = 25°C) MAX828 MAX829 8.4 24.5 12 35 15.6 45.5 — 96 — 95 99.9 — — 25 — IDD PEFF Characteristic Unit µA Power Efficiency ILOAD = 3mA, TA = 25°C V kHz % VEFF Voltage Conversion Efficiency (RLOAD = ROUT Output Resistance (Note 1.) IOUT = 5mA, TA = 25°C TA = 0°C to +85°C R) % W 50 65 1. Capacitors C1 and C2 contribution is approximately 20% of the output impedance. For additional information, refer to Equation 1 in the Applications Information section. ELECTRICAL CHARACTERISTICS (TA = –40°C to +85°C, VIN = +5V, C1 = C2 = 10µF (MAX828), C1 = C2 = 3.3µF (MAX829), unless otherwise noted. Typical values are at TA = 25°C.) (Note 2.) Characteristic Min Typ Max Supply Current MAX828 MAX829 — — — — 115 325 Vin Supply Voltage Range (RLOAD = 10kW) 1.5 — 5.5 FOSC Oscillator Frequency MAX828 MAX829 6.0 19 — — 20 54.3 — — 65 Symbol IDD Unit µA V kHz ROUT Output Resistance (IOUT = 5mA) 2. All –40°C to +85°C specifications are guaranteed by design. http://onsemi.com 2 W MAX828 MAX829 DETAILED OPERATING DESCRIPTION The MAX828/829 charge pump converters invert the voltage applied to the VIN pin. Conversion consists of a two–phase operation (Figure 1). During the first phase, switches S2 and S4 are open and S1 and S3 are closed. During this time, C1 charges to the voltage on VIN and load current is supplied from C2. During the second phase, S2 and S4 are closed, and S1 and S3 are open. This action connects C1 across C2, restoring charge to C2. S1 (4) Losses that occur during charge transfer (from the commutation capacitor to the output capacitor) when a voltage difference between the two capacitors exists. Most of the conversion losses are due to factors (2), (3) and (4) above. These losses are given by Equation 1. ƪ S2 MAX828/829 R OUT ^ IOUT ƫ 2 )C1 Equation 1. The 1/(fOSC)(C1) term in Equation 1 is the effective output resistance of an ideal switched capacitor circuit (Figures 2a, 2b). The losses in the circuit due to factor (4) above are also shown in Equation 2. The output voltage ripple is given by Equation 3. C2 S3 OSC 2 ) 8RSWITCH ) 4ESRC1 ) ESRC2 1 (f IN C1 + IOUT P LOSS(2,3,4) S4 Vout = –(Vin) ƪ P LOSS(4) + (V ƪ (0.5)(C1)( V 2 IN 2 RIPPLE * VOUT ) ) (0.5)(C2) 2 * 2VOUT VRIPPLE) ƫ f OSC Equation 2. Figure 1. Ideal Switched Capacitor Charge Pump V RIPPLE APPLICATIONS INFORMATION + (f I OUT )(C2) OSC ) 2(IOUT)(ESRC2) Equation 3. Output Voltage Considerations The MAX828/829 perform voltage conversion but do not provide regulation. The output voltage will drop in a linear manner with respect to load current. The value of this equivalent output resistance is approximately 25W nominal at +25°C and VIN = +5V. VOUT is approximately - 5V at light loads, and droops according to the equation below: f V+ Vout C1 VDROP = IOUT x ROUT VOUT = – (VIN – VDROP) C2 RL Figure 2a. Ideal Switched Capacitor Model Charge Pump Efficiency REQUIV V+ The overall power efficiency of the charge pump is affected by four factors: Vout R (1) Losses from power consumed by the internal oscillator, switch drive, etc. (which vary with input voltage, temperature and oscillator frequency). (2) I2R losses due to the on–resistance of the MOSFET switches on–board the charge pump. (3) Charge pump capacitor losses due to effective series resistance (ESR). EQUIV +f 1 C1 C2 RL Figure 2b. Equivalent Output Resistance http://onsemi.com 3 MAX828 MAX829 Capacitor Selection 1 2 C1+ OUT IN Vout C2 3.3 mF* 5 + + MAX828 MAX829 In order to maintain the lowest output resistance and output ripple voltage, it is recommended that low ESR capacitors be used. Additionally, larger values of C1 will lower the output resistance and larger values of C2 will reduce output ripple. (See Equation 3). Table 1 shows various values of C1 and the corresponding output resistance values at +25°C. It assumes a 0.1W ESRC1 and 0.5W RSW. Table 2 shows the output voltage ripple for various values of C2. The VRIPPLE values assume 10mA output load current and 0.1W ESRC2. Vin + C3 3.3 mF* RL C1 3.3 mF* GND 4 – 3 C1 Table 1. Output Resistance vs. C1 (ESR = 0.1Ω) C1(µF) MAX828 ROUT (W) MAX829 ROUT (W) 0.1 1.7k 580 1 170 61 3.3 55 21 Cascading Devices 10 21 10 47 8.0 5.7 100 6.2 5.1 Two or more MAX828/829’s can be cascaded to increase output voltage (Figure 4). If the output is lightly loaded, it will be close to (- 2 x VIN) but will droop at least by ROUT of the first device multiplied by the IQ of the second. It can be seen that the output resistance rises rapidly for multiple cascaded devices. Figure 3. Test Circuit Table 2. Output Voltage Ripple vs. C2 (ESR = 0.1W) IOUT = 10mA C2(µF) MAX828 VRIPPLE (mV) MAX829 VRIPPLE (mV) 1 830 290 3.3 250 87 10 83 28 47 17 6.1 100 8.3 2.9 *10 mF (MAX828) Voltage Inverter Vin+ 3 C1 + 4 2 3 C1 + MAX828 MAX829 “1” 4 2 MAX828 MAX829 “n” Input Supply Bypassing Vout The VIN input should be capacitively bypassed to reduce AC impedance and minimize noise effects due to the switching internal to the device. The recommended capacitor depends on the configuration of the MAX828/829. If the device is loaded from OUT to GND it is recommended that a large value capacitor (at least equal to C1) be connected from the input to GND. If the device is loaded from IN to OUT a small (0.1µF) capacitor from IN to OUT is sufficient. 5 5 1 C2 1 C2 + + Vout = –nVin Figure 4. Cascading MAX828s or MAX829s to Increase Output Voltage Paralleling Devices To reduce the value of ROUT, multiple MAX828/829s can be connected in parallel (Figure 5). The output resistance will be reduced by a factor of N where N is the number of MAX828/829’s. Each device will require it’s own pump capacitor (C1), but all devices may share one reservoir capacitor (C2). However, to preserve ripple performance the value of C2 should be scaled according to the number of paralleled MAX828/829’s. Voltage Inverter The most common application for charge pump devices is the inverter (Figure 3). This application uses two external capacitors - C1 and C2 (plus a power supply bypass capacitor, if necessary). The output is equal to –VIN plus any voltage drops due to loading. Refer to Table 1 and Table 2 for capacitor selection. http://onsemi.com 4 MAX828 MAX829 R out out OF SINGLE DEVICE + RNUMBER OF DEVICES Diode Protection for Heavy Loads When heavy loads require the OUT pin to sink large currents being delivered by a positive source, diode protection may be needed. The OUT pin should not be allowed to be pulled above ground. This is accomplished by connecting a Schottky diode (1N5817) as shown in Figure 7. Vin+ 3 C1 + 4 2 3 C1 + MAX828 MAX829 “1” 4 2 MAX828 MAX829 “n” ... GND Vout 5 5 1 MAX828 MAX829 1 Vout = Vin– C2 + OUT Figure 5. Paralleling MAX828s or MAX829s to Reduce Output Resistance Layout Considerations As with any switching power supply circuit good layout practice is recommended. Mount components as close together as possible to minimize stray inductance and capacitance. Also use a large ground plane to minimize noise leakage into other circuitry. Another common application of the MAX828/829 is shown in Figure 6. This circuit performs two functions in combination. C1 and C2 form the standard inverter circuit described above. C3 and C4 plus the two diodes form the voltage doubler circuit. C1 and C3 are the pump capacitors and C2 and C4 are the reservoir capacitors. Because both sub–circuits rely on the same switches if either output is loaded, both will droop toward GND. Make sure that the total current drawn from both the outputs does not total more than 40mA. Vin+ D1, D2 = 1N4148 2 C1 + 4 D1 MAX828 MAX829 5 1 + C2 D2 + C3 1 Figure 7. High V– Load Current Voltage Doubler/Inverter 3 4 + C4 Vout = Vin– Vout = (2Vin) – (VFD1) – (VFD2) Figure 6. Combined Doubler and Inverter http://onsemi.com 5 MAX828 MAX829 TYPICAL CHARACTERISTICS 80 60 70 OUTPUT RESISTANCE (W ) OUTPUT RESISTANCE (W ) Circuit of Figure 3, Vin = +5 V, C1 = C2 = C3, TA = +25°C, unless otherwise noted. 70 50 40 30 MAX829 MAX828 20 10 40 Vin = 3.3 V 30 20 Vin = 5.0 V 0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 –40 5.0 0 25 85 SUPPLY VOLTAGE (V) TEMPERATURE (°C) Figure 8. Output Resistance versus Supply Voltage Figure 9. Output Resistance versus Temperature 40 35 OUTPUT CURRENT (mA) 40 OUTPUT CURRENT (mA) 50 10 0 Vin = 4.75 V, Vout = –4.0 V 30 25 Vin = 3.15 V, Vout = –2.5 V 20 15 10 Vin = 1.9 V, Vout = –1.5 V 35 Vin = 4.75 V, Vout = –4.0 V 30 25 Vin = 3.15 V, Vout = –2.5 V 20 15 10 Vin = 1.9 V, Vout = –1.5 V 5 5 0 0 0 5 10 15 20 25 30 35 0 15 20 25 30 CAPACITANCE (mF) Figure 11. Output Current versus Capacitance (MAX829) Vin = 4.75 V, Vout = –4.0 V 350 10 CAPACITANCE (mF) 450 400 5 Figure 10. Output Current versus Capacitance (MAX828) OUTPUT VOLTAGE RIPPLE (mVp–p) OUTPUT VOLTAGE RIPPLE (mVp–p) Vin = 1.5 V 60 300 Vin = 3.15 V, Vout = –2.5 V 250 200 Vin = 1.9 V, Vout = –1.5 V 150 100 50 0 35 300 250 Vin = 4.75 V, Vout = –4.0 V 200 Vin = 3.15 V, Vout = –2.5 V 150 Vin = 1.9 V, Vout = –1.5 V 100 50 0 0 5 10 15 20 25 30 35 0 5 10 15 20 25 30 CAPACITANCE (mF) CAPACITANCE (mF) Figure 12. Output Voltage Ripple versus Capacitance (MAX828) Figure 13. Output Voltage Ripple versus Capacitance (MAX829) http://onsemi.com 6 35 MAX828 MAX829 TYPICAL CHARACTERISTICS Circuit of Figure 3, Vin = +5 V, C1 = C2 = C3, TA = +25°C, unless otherwise noted. 14 100 PUMP FREQUENCY (kHz) SUPPLY CURRENT ( m A) 120 MAX829 80 60 40 MAX828 20 12 Vin = 3.3 V 10 Vin = 1.5 V 8 6 4 2 0 0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 –40 25 85 SUPPLY VOLTAGE (V) TEMPERATURE (°C) Figure 15. Pump Frequency versus Temperature (MAX828) 0 Vin = 5.0 V 40 –1 OUTPUT VOLTAGE (V) 35 Vin = 3.3 V 30 25 Vin = 1.5 V 20 15 10 Vin = 2.0 V –2 Vin = 3.3 V –3 Vin = 5.0 V –4 –5 5 –6 0 25 85 0 10 20 30 40 TEMPERATURE (°C) OUTPUT CURRENT (mA) Figure 16. Pump Frequency versus Temperature (MAX829) Figure 17. Output Voltage versus Output Current 100 Vin = 5.0 V EFFICIENCY (%) 0 –40 0 Figure 14. Supply Current versus Supply Voltage 45 PUMP FREQUENCY (kHz) Vin = 5.0 V 80 Vin = 3.3 V Vin = 1.5 V 60 40 0 10 20 30 40 OUTPUT CURRENT (mA) Figure 18. Efficiency versus Output Current http://onsemi.com 7 50 50 MAX828 MAX829 TAPING FORM Component Taping Orientation for 5L SOT–23 Devices USER DIRECTION OF FEED DEVICE MARKING PIN 1 Standard Reel Component Orientation for TR Suffix Device (Mark Right Side Up) Tape & Reel Specifications Table Package Tape Width (W) Pitch (P) Part Per Full Reel Diameter 5L SOT–23 8 mm 4 mm 3000 7 inches MARKING SOT–23–5 1 2 3 4 MAX828/829 Marking MAX828SNTR MAX829SNTR CA CB 3 + 4 1 + 2 Date Code http://onsemi.com 8 MAX828 MAX829 PACKAGE DIMENSIONS SOT–23–5 PLASTIC PACKAGE CASE TBD ISSUE TBD 0.75 (1.90) REFERENCE .122 (3.10) .098 (2.50) .071 (1.80) .059 (1.50) .020 (0.50) .012 (0.30) .037 (0.95) REFERENCE .122 (3.10) .106 (2.70) .057 (1.45) .035 (0.90) 10 ° MAX. .006 (0.15) .000 (0.00) .010 (0.25) .004 (0.09) .022 (0.55) .008 (0.20) NOTE: SOT–23–5 is equivalent to EIAJ–SC74A Dimensions: inches (mm) http://onsemi.com 9 MAX828 MAX829 Notes http://onsemi.com 10 MAX828 MAX829 Notes http://onsemi.com 11 MAX828 MAX829 ON Semiconductor and are trademarks of Semiconductor Components Industries, LLC (SCILLC). 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