A S1 3 2 9 L o w Vo lt a g e, M i c ro p o w e r, D C- DC St ep - U p C o n v e r te r s 1 General Description 2 Key Features The AS1329A, AS1329B and the AS1329C are synchronous, fixed frequency, very high-efficiency DC-DC boost converters capable of supplying 3.3V at 160mA from a single AA-supply. Compact size and minimum external parts requirements make these devices perfect for modern portable devices. Low Start-Up Voltage: 0.85V High-speed switching frequency (1.2MHz) and internally compensated PWM current mode design provide highly-reliable DCDC conversion, especially when driving white LEDs. The converters are available as the standard products listed in Table 1. Operating with coils down to 2.2µH Output Range: 2.5V to 5.0V Single-Cell Operation Delivers 160mA @ 3.3V (from Single AA Cell) Delivers 220mA @ 5.0V (from Two AA Cells) Table 1. Standard Products Delivers 570mA @ 3.3V (from Two AA Cells) Model Light Load Switching AS1329A Medium Load Automatic Powersave Operation AS1329B Light Load Automatic Powersave Operation AS1329C Continuous Switching 95% Efficiency High-Speed Fixed-Frequency: 1.2MHz Internal PMOS Synchronous Rectifier Automatic Powersave Operation (AS1329A&B) The devices contain two internal MOSFET switches: one NMOS switch and one PMOS synchronous rectifier. Anti-ringing control circuitry reduces EMI by damping the inductor in discontinuous mode, and the devices exhibit extremely low quiescent current (< 1µA) in shutdown. Continuous Switching at Light Loads (AS1329C) Logic Controlled Shutdown (< 1µA) 6-pin TSOT-23 Package In shutdown mode the battery is connected directly to the output enabling the supply of real-time-clocks. The AS1329 is available in a 6-pin TSOT-23 package. 3 Applications The AS1329 is ideal for low-power applications where ultra-small size is critical as in medical diagnostic equipment, hand-held instruments, pagers, digital cameras, remote wireless transmitters, MP3 players, LCD bias supplies, cordless phones, GPS receivers, and PC cards. Figure 1. Typical Application Diagram – Single Cell to 3.3V Synchronous Boost Converter L1 4.7µH 1 SW 6 AA Battery 5 VOUT VIN C1 10µF On Off AS1329 4 C2 10µF 3 SHDNN FB 2 www.ams.com/DC-DC_Step-Up/AS1329 R1 1.02MΩ 1% VOUT 3.3V 160mA GND Revision 1.12 R2 604kΩ 1% 1 - 20 AS1329 Datasheet - P i n A s s i g n m e n t s 4 Pin Assignments Figure 2. Pin Assignments (Top View) SW 1 GND 2 6 VIN AS1329 FB 3 5 VOUT 4 SHDNN 4.1 Pin Descriptions Table 2. Pin Descriptions Pin Number Pin Name 1 SW 2 GND 3 FB 4 SHDNN 5 VOUT 6 VIN www.ams.com/DC-DC_Step-Up/AS1329 Description Switch Pin. Connect an inductor between this pin and VIN. Keep the PCB trace lengths as short and wide as is practical to reduce EMI and voltage overshoot. If the inductor current falls to zero, or pin SHDNN is low, an internal 100Ω anti-ringing switch is connected from this pin to VIN to minimize EMI. Note: An optional Schottky diode can be connected between this pin and VOUT. Signal and Power Ground. Provide a short, direct PCB path between this pin and the negative side of the output capacitor(s). Feedback Pin. Feedback input to the gm error amplifier. Connect a resistor divider tap to this pin. The output voltage can be adjusted from 2.5 to 5V by: VOUT = 1.23V[1 + (R1/R2)] Shutdown Pin. Logic controlled shutdown input. 1 = Normal operation, 1.2MHz typical operating frequency. 0 = Shutdown; quiescent current <1µA. If SHDNN is undefined, pin SW may ring. Note: In a typical application, SHDNN should be connected to VIN through a 1MΩ pull-up resistor. Output Voltage Sense Input and Drain of the Internal PMOS Synchronous Rectifier. Bias is derived from VOUT when VOUT exceeds VIN. PCB trace length from VOUT to the output filter capacitor(s) should be as short and wide as is practical. Input Voltage. The AS1329 gets its start-up bias from VIN unless VOUT exceeds VIN, in which case the bias is derived from VOUT. Thus, once started, operation is completely independent from VIN. Operation is only limited by the output power level and the internal series resistance of the supply. Revision 1.12 2 - 20 AS1329 Datasheet - A b s o l u t e M a x i m u m R a t i n g s 5 Absolute Maximum Ratings Stresses beyond those listed in Table 3 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 Section 6 Electrical Characteristics on page 4 is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Table 3. Absolute Maximum Ratings Parameter Min Max Units VIN to GND -0.3 7 V SHDNN, SW to GND -0.3 7 V FB to GND -0.3 5 V VOUT -0.3 7 V Operating Temperature Range -40 +85 ºC Storage Temperature Range -65 +125 ºC Package Body Temperature Moisture Sensitive Level www.ams.com/DC-DC_Step-Up/AS1329 +260 1 ºC Notes The reflow peak soldering temperature (body temperature) specified is in accordance with IPC/ JEDEC J-STD-020 “Moisture/Reflow Sensitivity Classification for Non-Hermetic Solid State Surface Mount Devices”. The lead finish for Pb-free leaded packages is matte tin (100% Sn). Represents an unlimited floor life time Revision 1.12 3 - 20 AS1329 Datasheet - E l e c t r i c a l C h a r a c t e r i s t i c s 6 Electrical Characteristics TAMB = -40°C to +85ºC, VIN = +1.2V, VOUT = +3.3V, VSHDNN = +1.2V (unless otherwise specified). Typ values @ TAMB = +25ºC. Table 4. Electrical Characteristics Symbol VFB Parameter Conditions Min Minimum Start-Up Voltage ILOAD = 1mA Minimum Operating Voltage SHDNN = VIN Maximum Operating Voltage SHDNN = VIN Output Voltage Adjust Range TAMB = 25ºC 2.5 Feedback Voltage TAMB = TMIN to TMAX 1.192 1 Typ Max Units 0.85 1 V 0.65 0.85 V 5 V 5 V 1.268 V 1 2 1.23 IFB Feedback Input Current VFB = 1.25V IQPWS Quiescent Current (Powersave Operation) VFB = 1.4V , AS1329A only 30 50 µA ISHDNN Shutdown Current VSHDNN = 0V 0.01 1 µA IQ Quiescent Current (Active) VFB = 1.4V , AS1329B&C only 150 300 µA INMOSSWL NMOS Switch Leakage VSW = 5V 0.1 5 µA IPMOSSWL PMOS Switch Leakage VSW = 0V 0.1 5 µA VOUT = 3.3V 0.35 0.8 RONNMOS NMOS Switch On Resistance 4 0.20 0.7 VOUT = 3.3V 0.45 0.8 4 0.30 0.7 3 3 VOUT = 5V RONPMOS PMOS Switch On Resistance VOUT = 5V INMOS IPS NMOS Current Limit 1 VIN = 2.5V nA 850 mA 3 mA 2 0.3 mA % AS1329A only Max Duty Cycle VFB = 1V, TAMB = TMIN to TMAX 80 87 TAMB = 25ºC 0.95 1.2 1.5 TAMB = TMIN to TMAX 0.85 1.2 1.5 fSW Switching Frequency VSHDNNH SHDNN Input High VSHDNNL SHDNN Input Low ISHDNN SHDNN Input Current Ω 2 Powersave Operation Current Threshold AS1329B only Ω 1 VSHDNN = 5.0V MHz V 0.01 0.35 V 1 µA 1. Minimum VIN operation after start-up is only limited by the battery’s ability to provide the necessary power as it enters a deeply discharged state. 2. Specification is guaranteed by design and not 100% production tested. 3. IQPWS is measured at VOUT. Multiply this value by VOUT/VIN to get the equivalent input (battery) current. 4. Specification is guaranteed by design and not 100% production tested. Note: All limits are guaranteed. The parameters with min and max values are guaranteed with production tests or SQC (Statistical Quality Control) methods. www.ams.com/DC-DC_Step-Up/AS1329 Revision 1.12 4 - 20 AS1329 Datasheet - Ty p i c a l O p e r a t i n g C h a r a c t e r i s t i c s 7 Typical Operating Characteristics All measurements are performed with AS1329A, VOUT = 3.3V, TAMB = +25ºC, unless otherwise specified. Parts used for measurements: L= 10µH (MOS6020-103ML), CIN and COUT = 10µF (GRM31CR70J106KA01L) Figure 4. VOUT vs. Temperature; IOUT = 10mA 3.5 3.36 3 3.34 Output Voltage (V) . Output Voltage (V) . Figure 3. VOUT vs. Battery Voltage; IOUT = 10mA 2.5 2 1.5 1 3.32 3.3 3.28 3.26 0.5 0 0 0.5 1 1.5 2 2.5 3 3.24 -50 3.5 -25 Battery Voltage (V) Figure 5. Startup Voltage vs. Output Current 25 50 75 100 Figure 6. Powersave threshold vs. Input Voltage 1.8 120 AS1329A 1.7 Vout = 3.3V AS1329B Vout = 5.0V 1.6 Output Current (mA) . Startup Voltage (V) . 0 Temperature (°C) 1.5 1.4 1.3 1.2 1.1 1 0.9 100 80 60 40 20 0.8 0.7 0 0.1 1 10 100 1 1.25 Output Current (mA) 1.5 1.75 2 2.25 2.5 Battery Voltage (V) Figure 7. IOUT vs. VBATT; VOUT = 3.3V, 3% Tolerance Figure 8. IOUT vs. VBATT; VOUT = 5.0V, 3% Tolerance . 800 800 700 Output Current (mA) 900 . 900 Output Current (mA) 1000 700 600 500 400 300 200 600 500 400 300 200 100 100 0 0 0.5 1 1.5 2 2.5 3 0.5 Battery Voltage (V) www.ams.com/DC-DC_Step-Up/AS1329 1 1.5 2 2.5 3 3.5 4 Battery Voltage (V) Revision 1.12 5 - 20 AS1329 Datasheet - Ty p i c a l O p e r a t i n g C h a r a c t e r i s t i c s Figure 9. No Load Battery Current vs. Battery Voltage; Figure 10. Efficiency vs. Battery Voltage; AS1329A 1000 100 80 Efficiency (%) . Battery Current (µA) . 90 100 70 60 50 40 Il oad = 80µA 30 Il oad = 800µA Il oad = 11mA 10 20 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 0.7 1.2 Battery Voltage (V) 2.2 2.7 3.2 Figure 12. Efficiency vs. Output Current of AS1329B 100 100 90 90 80 80 Efficiency (%) . Efficiency (%) . Figure 11. Efficiency vs. Output Current of AS1329A 70 60 50 40 70 60 50 40 Vi n = 1.0V Vi n = 1.5V 30 Vi n = 1.0V Vi n = 1.5V 30 Vi n = 2.2V Vi n = 2.4V 20 Vi n = 2.2V Vi n = 2.4V 20 0.1 1 10 100 1000 0.1 Output Current (mA) 1 10 100 1000 Output Current (mA) Figure 13. Efficiency vs. Output Current of AS1329C Figure 14. Efficiency vs. IOUT Comparison; VIN = 2.0V 100 100 90 90 80 80 Efficiency (%) . Efficiency (%) . 1.7 Battery Voltage (V) 70 60 50 40 70 60 50 40 AS1329A Vin = 1.0V 30 Vin = 1.5V 30 AS1329B Vin = 2.2V 20 AS1329C 20 0.1 1 10 100 1000 1 Output Current (mA) www.ams.com/DC-DC_Step-Up/AS1329 10 100 Output Current (mA) Revision 1.12 6 - 20 AS1329 Datasheet - Ty p i c a l O p e r a t i n g C h a r a c t e r i s t i c s Figure 16. SW Pin Fixed Frequency Continuous Current; VIN = 1.3V, L=10µH, C=10µF, IOUT = 100mA 1V/Div 100ns/Div 100ns/Div 100mV/Div 60mA VOUT(AC) IOUT 1mA 100mV/Div Figure 18. Fixed Frequency vs. Powersave Operation; VIN = 1.3V, L = 10µH, C = 10µF 100mA VIN = 1.3V, 40mA IOUT VOUT(AC) Figure 17. VOUT Transient Response; L = 10µH, C = 10µF 0V VSW 0V VSW 1V/Div Figure 15. SW Pin Antiringing Operation; VIN = 1.3V, L = 10µH, C = 10µF, IOUT = 5mA 100µs/Div www.ams.com/DC-DC_Step-Up/AS1329 10ms/Div Revision 1.12 7 - 20 AS1329 Datasheet - D e t a i l e d D e s c r i p t i o n 8 Detailed Description The AS1329 can operate from a single-cell input voltage (VIN) below 1V, and features fixed frequency (1.2MHz) and current mode PWM control for exceptional line- and load-regulation. With low RDS(ON) and gate charge internal NMOS and PMOS switches, the device maintains highefficiency from light to heavy loads. Modern portable devices frequently spend extended time in low-power or standby modes, switching to high power-drain only when certain functions are enabled. The AS1329A, AS1329B and AS1329C are ideal for portable devices since they maintain high-power conversion efficiency over a wide output power range, thus increasing battery life in these types of devices. In addition to high-efficiency at moderate and heavy loads, the AS1329A as well as the AS1329B includes an automatic powersave mode that improves efficiency of the power converter at light loads. The powersave mode is initiated if the output load current falls below a factory programmed threshold (see Figure 6 on page 5). Note: The AS1329C does not support powersave mode and provides continuous operation at all loads, eliminating low-frequency VOUT ripple at the expense of light load efficiency. Figure 19. AS1329 - Block Diagram L1 4.7µH 1.5V Single Cell 6 VIN Start Up OSC CIN 1µF 1 SW 2.3V – A B VOUT Good A/B MUX PWM Control 1.2MHz Ramp Generator Slope Compensator + VOUT 0.45Ω 0.35Ω Sync Drive Control CFF* Current Sense Σ AS1329 + PWM – Comp – 4 SHDNN Shutdown Control Powersave Shutdown Powersave Operation Control RC 80kΩ CC 150pF 3.3V Output 5 3 – gm Error Amp + R1 1.02MΩ 1% COUT 4.7µF FB CP2 2.5pF R2 640kΩ 1% 1.23V Ref 2 GND * Optional 8.1 Low-Voltage Start-Up The AS1329 requires VIN of only 0.85V (typ) or higher to start up. The low-voltage start-up circuitry controls the internal NMOS switch up to a maximum peak inductor current of 850mA (typ), with 1.5ms (approx.) off-time during start-up, allowing the devices to start up into an output load. With a VOUT > 2.3V, the start-up circuitry is disabled and normal fixed-frequency PWM operation is initiated. In this mode, the AS1329 operates independent of VIN, allowing extended operating time as the battery can drop to several tenths of a volt without affecting output regulation. The limiting factor for the application is the ability of the battery to supply sufficient energy to the output. www.ams.com/DC-DC_Step-Up/AS1329 Revision 1.12 8 - 20 AS1329 Datasheet - D e t a i l e d D e s c r i p t i o n 8.2 Low-Noise Fixed-Frequency Operation 8.2.1 Oscillator The AS1329 switching frequency is internally fixed at 1.2MHz allowing the use of very small external components. 8.2.2 Error Amplifier The integrated error amplifier is an internally compensated trans-conductance (gm) type (current output). The internal 1.23V reference voltage is compared to the voltage at pin FB to generate an error signal at the output of the error amplifier. A voltage divider from VOUT to GND programs the output voltage from 2.5 to 5V via pin FB as: VOUT = 1.23V(1 + (R1/R2)) 8.2.3 (EQ 1) Current Sensing A signal representing the internal NMOS-switch current is summed with the slope compensator. The summed signal is compared to the error amplifier output to provide a peak current control command for the PWM. Peak switch current is limited to approximately 850mA independent of VIN or VOUT. 8.2.4 Zero Current Comparator The zero current comparator monitors the inductor current to the output and shuts off the PMOS synchronous rectifier once this current drops to 20mA (approx.). This prevents the inductor current from reversing polarity and results in improved converter efficiency at light loads. 8.2.5 Anti-Ringing Control Anti-ringing control circuitry prevents high-frequency ringing on pin SW as the inductor current approaches zero. This is accomplished by damping the resonant circuit formed by the inductor and the capacitance on pin SW (CSW). 8.3 Powersave Operation (AS1329A, AS1329B) In light load conditions, the integrated powersave feature removes power from all circuitry not required to monitor VOUT. When VOUT has dropped approximately 1% from nominal, the AS1329A & B powers up and begins normal PWM operation. COUT (see Figure 19 on page 8) recharges, causing the AS1329A and AS1329B to re-enter powersave mode as long as the output load remains below the powersave threshold. The frequency of this intermittent PWM is proportional to load current; i.e., as the load current drops further below the powersave threshold, the AS1329A and AS1329B turns on less frequently. When the load current increases above the powersave threshold, the AS1329A and AS1329B will resume continuous, seamless PWM operation. While the AS1329A switches to automatic powersave mode already at medium loads, the AS1329B will do so only at very light loads. The AS1329C is a continuous switching device, hence the output voltage ripple is very low and no additional frequencies are produced which may cause interference. Notes: 1. An optional capacitor (CFF) between pins VOUT and FB in some applications can reduce VOUTp-p ripple and input quiescent current during powersave mode. Typical values for CFF range from 15 to 220pF. 2. In powersave mode, the AS1329A and AS1329B draws only 30µA from the output capacitor(s), greatly improving converter efficiency. 8.4 Shutdown When pin SHDNN is low the AS1329 is switched off and <1µA current is drawn from battery; when pin SHDNN is high the device is switched on. If SHDNN is driven from a logic-level output, the logic high-level (on) should be referenced to VOUT to avoid intermittently switching the device on. Note: If pin SHDNN is not used, it should be connected directly to pin OUT. In shutdown the battery input is connected to the output through the inductor and the internal synchronous rectifier P-FET. This allows the input battery to provide backup power for devices such as an idle microcontroller, memory, or real-time-clock, without the usual diode forward drop. In this way a separate backup battery is not needed. In cases where there is residual voltage during shutdown, some small amount of energy will be transferred from pin OUT to pin BATT immediately after shutdown, resulting in a momentary spike of the voltage at pin BATT. The ratio of CIN and COUT partly determine the size and duration of this spike, as does the current-sink ability of the input device. www.ams.com/DC-DC_Step-Up/AS1329 Revision 1.12 9 - 20 AS1329 Datasheet - A p p l i c a t i o n I n f o r m a t i o n 9 Application Information The AS1329 is perfectly suited for LED matrix displays, bar-graph displays, instrument-panel meters, dot matrix displays, set-top boxes, white goods, professional audio equipment, medical equipment, industrial controllers to name a few applications. Along with Figure 1 on page 1, Figures 20-23 depict a few of the many applications for which the AS1329 converters are perfectly suited. Figure 20. Single AA Cell to 3.3V Synchronous Boost Converter with Load Disconnect in Shutdown L1 4.7µH D1 1 SW 5 6 AA Battery C1 4.7µF On Off VOUT 3.3V, 160mA VOUT C2 4.7µF VIN AS1329 4 R3 510kΩ R1 1.02MΩ 1% 3 SHDNN FB 2 R2 604kΩ 1% GND Q1 R3 510kΩ Figure 21. Single Lithium Cell to 5V, 250mA 2Ω Optional Snubber 100nF L1 4.7µH D1 1 SW 5 6 Lithium Battery VIN C1 4.7µF On Off AS1329 4 R1 1.02MΩ 1% C3 100pF 3 SHDNN FB 2 www.ams.com/DC-DC_Step-Up/AS1329 VOUT C2 4.7µF GND Revision 1.12 R2 332kΩ 1% 10 - 20 AS1329 Datasheet - A p p l i c a t i o n I n f o r m a t i o n Figure 22. Single AA Cell to ±3V Synchronous Boost Converter C3 1µF L1 4.7µH 1 SW AA Battery C1 4.7µF VOUT C2 4.7µF R1 1.02MΩ 1% AS1329 On Off VOUT1 3V, 90mA 5 6 VIN 3 4 D1 FB SHDNN 2 D2 C4 10µF R2 750kΩ 1% GND VOUT2 -3V, 10mA Figure 23. Single AA Cell to 2.5V Synchronous Boost Converter L1 4.7µH D1 1 SW 5 6 AA Battery C1 10µF On Off R1 1.02MΩ 1% AS1329 C2 10µF 3 4 SHDNN FB 2 www.ams.com/DC-DC_Step-Up/AS1329 VOUT 2.5V, 230mA VOUT VIN GND Revision 1.12 R2 1.02MΩ 1% 11 - 20 AS1329 Datasheet - A p p l i c a t i o n I n f o r m a t i o n 9.1 Output Voltage Ripple The AS1329 is designed to work at high efficiency. In order to reduce the output ripple the following improvements are recommended: Use a higher output capacitor, up to 44µF and a higher input capacitor (22µF). Use smaller values for the resistor divider. R1 should be about 300kΩ. To avoid a high leakage current from pin VOUT through the resistor divider to GND, R1 should not be less than 100kΩ.. To reduce the output ripple it’s also possible to speed up the feedback loop. To achieve this, place a 22pF (C4 in Figure 24) capacitor in parallel to R1. Via C4 the fast transients are shorted to the FB pin and the feedback loop is even faster. A 1MΩ resistor for R1 slows down the FB loop. Due to noise and to their non linear behavior, the use of potentiometers is not recommended. Figure 24. AS1329 - Typical Application for lower Output Voltage Ripple L1 4.7µH 1 2xAA Battery SW C1 22µF VOUT C4 22pF AS1329 On Off VOUT = 2.8V 5 6 VIN R1 250kΩ C2 22µF C3 22µF 3 4 FB SHDNN 2 GND R2 196kΩ Note: For correct measurements of the output ripple connect the oscilloscope probe as close as possible to the positive plate of the COUT and connect the GND of the oscilloscope probe to the negative plate of the COUT. This will reduce the inductive coupling and will deliver a more accurate measurement result. The output ripple is getting higher as VIN is getting closer to VOUT. Figure 25 shows that the above mentioned improvements reduce the output voltage ripple. If VIN is higher than VOUT the AS1329 stops switching and VIN is connected to VOUT via the inductor and the internal P-FET. Figure 25. Output Voltage Ripple vs. Input Voltage; VOUT = 2.8V, IOUT = 0.8mA Output Voltage Ripple (mVpp) 125 Cout = 44µF Cout = 66µF 100 Cout = 44µF + C4 = 22pF 75 50 25 0 0.5 1 1.5 2 2.5 3 3.5 Input Voltage (V) www.ams.com/DC-DC_Step-Up/AS1329 Revision 1.12 12 - 20 AS1329 Datasheet - A p p l i c a t i o n I n f o r m a t i o n 9.2 Smallest External Components The AS1329 is also able to work with smallest Capacitors and Inductors (see Figure 26). Figure 26. AS1329 - Typical Application for Smallest External Components L1 2.2µH 1 2xAA Battery SW VOUT VIN C1 2.2µF VOUT = 5V 5 6 AS1329 On Off C2 4.7µF R1 kΩ 3 4 SHDNN FB 2 R2 kΩ GND Table 5. Recommended Smallest Components Part Number Value Code Rating Size C1 GRM188R61A225KE34 2.2µF X5R 10V 0603 C2 GRM188R60J475KE19 4.7µF X5R 6.3V 0603 L1 LQM31PN2R2M00 2.2µH 238mΩ 0.9A 1206 Manufacturer Murata www.murata.com Figure 27. Efficiency vs. Output Current with Smallest External Components 100 90 Efficiency (%) . 80 70 60 50 40 Vi n = 3.3V 30 Vi n = 3.5V Vi n = 3.8V 20 1 10 100 1000 Output Current (mA) www.ams.com/DC-DC_Step-Up/AS1329 Revision 1.12 13 - 20 AS1329 Datasheet - A p p l i c a t i o n I n f o r m a t i o n 9.3 External Component Selection 9.3.1 Inductor Selection The fast switching frequency (1.2MHz) of the AS1329 allows for the use of small surface mount or chip inductor for the external inductor (see Figure 19 on page 8). The required minimum values for the external inductor are: 3.3µH for applications ≤ 3.6V 4.7µH for applications > 3.6V Larger inductor values allow greater output current capability by reducing the inductor ripple current. Increasing the inductance above 10µH will increase size while providing negligible improvement in output current capability. The approximate output current capability of the AS1329 versus inductor value is given in: V IN ⋅ D I OUT ( MAX ) = η ⋅ I P – ------------------ ⋅ ( 1 – D ) f ⋅ L ⋅ 2 (EQ 2) Where: η is the estimated efficiency; IP is the peak current limit value (0.6A); VIN is the input voltage; D is the steady-state duty ratio = (VOUT - VIN)/VOUT; f is the switching frequency (1.2MHz typ); L is the inductor value. The inductor current ripple is typically set for 20 to 40% of the maximum inductor current (IP). High-frequency ferrite core inductor materials reduce frequency dependent power losses compared to less expensive powdered iron types, which result in improved converter efficiency. The inductor should have low ESR to reduce the I²R power losses, and must be able to handle the peak inductor current without saturating. Molded chokes and some chip inductors normally do not have enough core to support the peak inductor currents of the AS1329 (850mA typ). To minimize radiated noise, use a toroid, pot core, or shielded bobbin inductor. Table 6. Recommended Inductors Part Number L DCR Current Rating Dimensions (L/W/T) MOS6020-103ML 10µH 93mΩ 1A 6.8x6.0x2.4mm MOS6020-472ML 4.7µH 50mΩ 1.5A 6.8x6.0x2.4mm MOS6020-332ML 3.3µH 46mΩ 1.8A 6.8x6.0x2.4mm CDRH4D18-100 10µH 200mΩ 0.61A 6.9x5.0x2.0mm CDRH4D18-6R8 6.8µH 200mΩ 0.76A 6.9x5.0x2.0mm CR43-6R8 6.8µH 131.2mΩ 0.95A 4.8x4.3x3.5mm CDRH4D18-4R7 4.7µH 162mΩ 0.84A 6.9x5.0x2.0mm www.ams.com/DC-DC_Step-Up/AS1329 Revision 1.12 Manufacturer Coilcraft www.coilcraft.com Sumida www.sumida.com 14 - 20 AS1329 Datasheet - A p p l i c a t i o n I n f o r m a t i o n Figure 28. Efficiency Comparison of Different Inductors, VIN = 1.5V, VOUT = 3.3V 90 92 85 90 80 88 Efficiency (%) Efficiency (%) 75 70 65 60 10uH - Coi l cr af t (M OS6020-103M L) 55 86 84 82 10uH - Sumi da(CDRH4D18-100) 10uH - Coi l c r af t (M OS6020-103M L) 80 6. 8uH - Sumi da(CDRH4D18-6R8) 50 10uH - Sumi da(CDRH4D18-100) 6. 8uH - Sumi da(CR43-6R8) 6. 8uH - Sumi da(CDRH4D18-6R8) 6. 8uH - Sumi da(CR43-6R8) 4. 7uH - Coi l cr af t(M OS6020-472M L) 45 78 4. 7 uH - Sumi da(CDRH4D18-4R7) 4. 7uH - Coi l c r af t (M OS6020-472M L) 4. 7 uH - Sumi da(CDRH4D18-4R7) 3. 3 uH - Coi l c r af t (M OS6020-332M L) 3. 3 uH - Coi l cr af t (M OS6020-332M L) 40 76 0.1 1 10 10 Output Current (mA) 9.3.2 Output Current (mA) 100 Output Capacitor Selection Low ESR capacitors should be used to minimize VOUT ripple. Multi-layer ceramic capacitors are recommended since they have extremely low ESR and are available in small footprints. A 2.2 to 10µF output capacitor is sufficient for most applications. Larger values up to 22µF may be used to obtain extremely low output voltage ripple and improve transient response. An additional phase lead capacitor may be required with output capacitors larger than 10µF to maintain acceptable phase margin. X5R and X7R dielectric materials are recommended due to their ability to maintain capacitance over wide voltage and temperature ranges. Table 7. Recommended Output Capacitor Part Number C TC Code Rated Voltage Dimensions (L/W/T) JMK212BJ226MG-T 22µF ±20% X5R 6.3V 2x1.3x1.3mm Manufacturer Taiyo Yuden www.t-yuden.com Input Capacitor Selection. Low ESR input capacitors reduce input switching noise and reduce the peak current drawn from the battery. Ceramic capacitors are recommended for input decoupling and should be located as close to the device as is practical. A 4.7µF input capacitor is sufficient for most applications. Larger values may be used without limitations. Table 8. Recommended Input Capacitor Part Number C TC Code Rated Voltage Dimensions (L/W/T) GRM31CR70J106KA01L 10µF ±10% X7R 6.3V 3.2x1.6x1.6mm Manufacturer Murata www.murata.com Diode Selection. A Schottky diode should be used to carry the output current for the time it takes the PMOS synchronous rectifier to switch on. For VOUT < 4.5V a Schottky diode is optional, although using one will increase device efficiency by 2% to 3%. Note: Do not use ordinary rectifier diodes, since the slow recovery times will compromise efficiency. www.ams.com/DC-DC_Step-Up/AS1329 Revision 1.12 15 - 20 AS1329 Datasheet - A p p l i c a t i o n I n f o r m a t i o n 9.4 PCB Layout Guidelines The high-speed operation of the AS1329 requires proper layout for optimum performance. Figure 29 shows the recommended component layout. A large ground pin copper area will help to lower the device temperature. A multi-layer board with a separate ground plane is recommended. Traces carrying large currents should be direct. Trace area at pin FB should be as small as is practical. The lead-length to the battery should be as short as is practical. Figure 29. Recommended Single-Layer Component Placement Optional VIN 6 1 SW AS1329 VIN R2 2 GND VOUT 5 CIN SHDNN 3 FB R1 SHDNN 4 COUT VOUT www.ams.com/DC-DC_Step-Up/AS1329 Revision 1.12 16 - 20 AS1329 Datasheet - P a c k a g e D r a w i n g s a n d M a r k i n g s 10 Package Drawings and Markings The device is available in a 6-pin TSOT-23 package. Figure 30. 6-pin TSOT-23 Package www.ams.com/DC-DC_Step-Up/AS1329 Revision 1.12 17 - 20 AS1329 Datasheet - P a c k a g e D r a w i n g s a n d M a r k i n g s Figure 31. 6-pin TSOT-23 Marking Pin1 Top ZZZZ Bottom XXXX Pin1 Package Code: ZZZZ - Marketingcode XXXX - encoded Datecode www.ams.com/DC-DC_Step-Up/AS1329 Revision 1.12 18 - 20 AS1329 Datasheet - O r d e r i n g I n f o r m a t i o n 11 Ordering Information The device is available as the standard products listed in Table 9. Table 9. Ordering Information Ordering Code Marking Description Delivery Form Package AS1329A-BTTT ASPA Low Voltage, Micropower, DC-DC Step-Up Converter with Automatic Powersave Operation beginning at Medium Loads Tape and Reel 6-pin TSOT-23 AS1329B-BTTT ASPB Low Voltage, Micropower, DC-DC Step-Up Converter with Automatic Powersave Operation beginning at Light Loads Tape and Reel 6-pin TSOT-23 AS1329C-BTTT ASPC Low Voltage, Micropower, DC-DC Step-Up Converter with Continuous Switching Tape and Reel 6-pin TSOT-23 Note: All products are RoHS compliant. Buy our products or get free samples online at ICdirect: http://www.ams.com/ICdirect Technical Support is found at http://www.ams.com/Technical-Support For further information and requests, please contact us mailto:[email protected] or find your local distributor at http://www.ams.com/distributor www.ams.com/DC-DC_Step-Up/AS1329 Revision 1.12 19 - 20 AS1329 Datasheet - O r d e r i n g I n f o r m a t i o n Copyrights Copyright © 1997-2010, ams AG, Tobelbaderstrasse 30, 8141 Unterpremstaetten, Austria-Europe. Trademarks Registered ®. All rights reserved. The material herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. All products and companies mentioned are trademarks or registered trademarks of their respective companies. Disclaimer Devices sold by ams AG are covered by the warranty and patent indemnification provisions appearing in its Term of Sale. ams AG makes no warranty, express, statutory, implied, or by description regarding the information set forth herein or regarding the freedom of the described devices from patent infringement. ams AG reserves the right to change specifications and prices at any time and without notice. Therefore, prior to designing this product into a system, it is necessary to check with ams AG for current information. This product is intended for use in normal commercial applications. Applications requiring extended temperature range, unusual environmental requirements, or high reliability applications, such as military, medical life-support or life-sustaining equipment are specifically not recommended without additional processing by ams AG for each application. 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Contact Information Headquarters ams AG Tobelbaderstrasse 30 A-8141 Unterpremstaetten, Austria Tel: +43 (0) 3136 500 0 Fax: +43 (0) 3136 525 01 For Sales Offices, Distributors and Representatives, please visit: http://www.ams.com/contact www.ams.com/DC-DC_Step-Up/AS1329 Revision 1.12 20 - 20