AS1341-BTDT

Datasheet AS1341 2 0 V, 6 0 0 m A , 1 0 0 % D u t y C y c le , St e p - D o w n C o n v e r t e r 1 General Description The AS1341 is a high-efficiency step-down converter with adjustable output voltages from 1.25V to VIN using supply voltages of up to 20V. An integrated current-limited 0.4Ω MOSFET delivers load currents up to 600mA. The AS1341 also includes a 100% duty cycle LDO mode with a low dropout of only 250mV for high efficiency if input voltages is in the range of the output voltage. The AS1341 has a low quiescent current (12µA) to improve light-load efficiency and minimize battery use, and draws only 0.8µA in shutdown mode. High switching frequencies (up to 200kHz) allow the use of small surface-mount inductors and output capacitors. The device is available in a TDFN-8 3x3mm pin package. 2 Key Features ! ! ! ! ! ! ! ! ! ! ! ! ! Output Voltages: Fixed 5V or Adjustable Input Voltage Range: 4.5V to 20V Output Current: Up to 600mA 1.25V Lowest Output Voltage Efficiency: up to 96% Quiescent Supply Current: 12µA Power-OK Output Internal 0.4Ω P-Channel MOSFET Shutdown Current: 0.8µA 100% Maximum Duty Cycle for Low Dropout Current-Limited Architecture Thermal Shutdown TDFN-8 3x3mm Package 3 Applications The device is ideal for notebook computers, distributed power systems, keep-alive supplies, and any other battery-operated, portable device. Figure 1. AS1341 - Typical Application VIN 4.5V to 20V 5 IN 4 LX D1 L1 VOUT = 5V CIN 7 SHDNN 6 ILIMIT 8 + COUT AS1341 OUT RPULL 3 POK 1 FB Indicates High-Power Trace 2 GND www.austriamicrosystems.com Revision 1.05 1 - 17 AS1341 Datasheet - P i n o u t 4 Pinout Pin Assignments Figure 2. Pin Assignments (Top View) FB 1 GND 2 8 OUT 7 SHDNN AS1341 POK 3 LX 4 9 6 ILIMIT 5 IN Pin Descriptions Table 1. Pin Descriptions Pin Number 1 2 3 4 5 6 7 8 9 Pin Name FB GND POK LX IN ILIMIT SHDNN OUT NC Note: Connect pin POK to GND when the Power-Ok feature is not used. Inductor Connection. Connect this pin to an external inductor. 4.5V to 20V Input Supply Voltage Peak Current Control Input. Connect this pin to IN or GND to set peak current limit (see Setting Current Limit on page 11). Shutdown Input. A low on this pin puts the AS1341 into shutdown mode. Supply current is reduced to 0.8µA and LX goes high-impedance. Regulated Output Voltage High-Impedance Sense Input. For the fixed 5V output connect this pin to VOUT. For adjustable output connect this pin to GND. Exposed Pad. This pad is not connected internally. Connect to GND or do not connect. Description Feedback Input. For the fixed 5V output connect this pin to GND. For adjustable output, connect to a resistive divider between VOUT and GND to set the output voltage between 1.25V and VIN. Ground Power OK. Active-low open-drain reset output. www.austriamicrosystems.com Revision 1.05 2 - 17 AS1341 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 2 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 Electrical Characteristics on page 4 is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Table 2. Absolute Maximum Ratings Parameter IN to GND LX to GND FB to GND ILIMIT, SHDNN, OUT, POK to GND Peak Input Current Thermal Resistance ΘJA Operating Temperature Range Storage Temperature Range Junction Temperature -40 -65 Min -0.3 -2 -0.3 -0.3 Max +23 VIN + 0.3 +5 VIN + 0.3 2 36.3 +85 +150 +150 Units V V V V A ºC/W ºC ºC ºC The reflow peak soldering temperature (body temperature) specified is in accordance with IPC/JEDEC J-STD-020D “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). on PCB Comments Package Body Temperature +260 ºC www.austriamicrosystems.com Revision 1.05 3 - 17 AS1341 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 DC Electrical Characteristics VIN = +12V, SHDNN = VIN, TAMB = -40 to +85ºC. Typical values are at TAMB = +25ºC (unless otherwise specified). Specifications based on circuit shown in Figure 1 on page 1. Table 3. Electrical Characteristics Symbol VIN VOUT VDROPOUT Parameter Input Voltage Range Output Voltage (Preset Output) Output Voltage (Adjustable) Dropout Voltage Line Regulation Load Regulation VFB IIN IINDROP Feedback Set Voltage (Adjustable Output) Input Supply Current Input Supply Current in Dropout Input Shutdown Current VUVLO Input Undervoltage Lockout Threshold OUT Bias Current IFB FB Bias Current FB Threshold Low Thermal Shutdown DC-DC Switches tOFFMIN tONMAX RLX ILXPEAK LX Switch Minimum Off-Time LX Switch Maximum On-Time LX Switch On-Resistance LX Current Limit LX Zero-Crossing Threshold Zero-Crossing Timeout LX Switch Leakage Current Control Inputs Digital Input Level SHDNN, ILIMIT = GND SHDNN, ILIMIT = IN 2.4 -100 90 92.5 +100 95 0.4 0.1 1 0.8 V nA % V µA LX does not rise above the threshold VIN = 20V, LX = GND, TAMB = +25ºC VIN = 20V, LX = GND VFB = 1.3V VIN = 6V VIN = 4.5V ILIMIT = GND, L = 39µH ILIMIT = IN, L = 10µH 500 1000 -75 30 0.1 1 0.2 8 0.4 10 0.4 0.5 700 1400 0.6 12 0.8 0.95 900 1800 +75 µs µs Ω mA mV µs µA 10ºC hysteresis No load No load SHDNN = GND VIN rising VIN falling VOUT = 5.5V VFB = 1.3V 3.6 3.5 2 -25 50 100 145 IOUT = 600mA, ILIMIT = VIN VIN = 6V to 20V, 200Ω load ILIMIT = VIN, IOUT = 0 to 500mA 1.212 FB = GND Conditions Min 4.5 4.85 1.25 250 0.1 1 1.25 12 45 0.8 4.0 3.9 3.5 1.288 18 60 3 4.4 4.3 5 +25 150 5.00 Typ Max 20 5.15 VIN Units V V mV %/V % V µA µA µA V µA nA mV ºC Digital Input Leakage Current VSHDNN, VILIMIT = 0 to 20V, VIN = 20V Power-OK Power-OK Threshold POK Output Voltage Low POK Output Leakage Current Falling edge, relative to VOUT IPOK = 1mA VIN, VPOK = 16V, TAMB = 25°C VIN, VPOK = 16V www.austriamicrosystems.com Revision 1.05 4 - 17 AS1341 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 VOUT = 5V, TAMB = +25ºC (unless otherwise specified); Figure 3. Efficiency vs. IOUT 100 95 90 ILIMIT = high VIN = 6V VIN = 12V Figure 4. Efficiency vs. IOUT 100 95 90 ILIMIT = low VIN = 6V VIN = 12V VIN = 20V Efficiency (%) . 85 80 75 70 65 60 55 50 0.1 1 10 100 1000 VIN = 20V Efficiency (%) . 85 80 75 70 65 60 55 50 0.1 1 10 100 1000 Output Current (mA) Output Current (mA) Figure 5. Efficiency vs. IOUT; VOUT = 3.3V 100 95 90 VIN = 4.5V ILIMIT = high Figure 6. Efficiency vs. IOUT; VOUT = 3.3V 100 95 90 ILIMIT = low VIN = 4.5V VIN = 12V VIN = 20V Efficiency (%) . Efficiency (%) . 85 80 75 70 65 60 55 50 0.1 1 10 100 1000 VIN = 12V VIN = 20V 85 80 75 70 65 60 55 50 0.1 1 10 100 1000 Output Current (mA) Output Current (mA) Figure 7. Efficiency vs. IOUT; VIN = 12V 95 90 ILIMIT = high Figure 8. Efficiency vs. IOUT; VIN = 12V 95 90 ILIMIT = low Efficiency (%) . 85 80 75 70 65 0.1 1 10 100 1000 22uH 10uH 4.1uH Efficiency (%) . 85 80 75 70 65 0.1 1 10 100 1000 10uH 39uH 22uH Output Current (mA) Output Current (mA) www.austriamicrosystems.com Revision 1.05 5 - 17 AS1341 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. Efficiency vs. Input Voltage; 100 95 Figure 10. Output Voltage vs. Input Voltage; 5.15 5.1 5.05 5 IOUT = 1mA IOUT = 100mA IOUT = 300mA IOUT = 500mA IOUT = 600mA Efficiency (%) . 85 80 VOUT=3.3V, IOUT=500mA 75 70 5 8 VOUT (V) . VOUT=5V, IOUT=500mA VOUT=3.3V, IOUT=250mA VOUT=5V, IOUT=250mA 90 4.95 4.9 4.85 11 14 17 20 5 8 11 14 17 20 Input Voltage (V) Input Voltage (V) Figure 11. Output Voltage vs. Input Voltage; VOUT = 3.3V 3.4 IOUT = 1mA IOUT = 300mA IOUT = 100mA Figure 12. Peak Switch Current vs. Input Voltage; VOUT = 3.3V 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 ILIMIT = high L=10µH ILIMIT = high L=39µH ILIMIT = low L=10µH ILIMIT = low L=39µH 3.35 IOUT = 500mA 3.3 3.25 Peak Switch Current (A) VOUT (V) . . 3.2 4 6 8 10 12 14 16 18 20 0 5 8 11 14 17 20 Input Voltage (V) Input Voltage (V) Figure 13. Switching Frequency vs. Output Current; VIN = 12V, VOUT = 5V, L = 10µH 250 Figure 14. Switching Frequency vs. Output Current; VIN = 12V, VOUT = 3.3V, L = 10µH 250 . Switching Frequency (kHz) 200 Switching Frequency (kHz) ILIMIT = low . 200 ILIMIT = low 150 150 100 ILIMIT = high 100 ILIMIT = high 50 50 0 0 100 200 300 400 500 600 0 0 100 200 300 400 500 600 Output Current (mA) Output Current (mA) www.austriamicrosystems.com Revision 1.05 6 - 17 AS1341 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 15. Load Regulation, VOUT vs. IOUT; VIN = 12V, VOUT = 5V 5.15 5.1 Figure 16. Load Regulation, VOUT vs. IOUT; VIN = 12V, VOUT = 3.3V 3.4 Output Voltage (V) . Output Voltage (V) . 3.35 ILIMIT = = high ILIMIT high 5.05 5 ILIMIT = high 3.3 ILIMIT = low ILIMIT = low ILIMIT = low 4.95 4.9 4.85 0 100 200 300 400 500 600 3.25 3.2 0 100 200 300 400 500 600 Output Current (mA) Output Current (mA) Figure 17. Line Transient Response; IOUT = 500mA Figure 18. Load Transient Response 100mV/Div 1A/Div ILX VOUT ILOAD 15V 10V VIN 500mA 10mA 10µs/Div 200µs/Div Figure 19. LX Waveform; VIN = 20V, IOUT = 500mA Figure 20. Startup Waveform; RLOAD = 100Ω 1A/Div IL 10V/Div VLX VOUT 50mV/Div VOUT VSHDNN 2µs/Div 100µs/Div www.austriamicrosystems.com Revision 1.05 5V/Div 5V 0V 1A/Div ILX 50mV/Div VOUT 10V/Div VLX 1A/Div ILX 7 - 17 AS1341 Datasheet - D e t a i l e d D e s c r i p t i o n 8 Detailed Description The AS1341 step-down converter was specifically designed for battery-powered portable devices, including laptop computers, PDAs, and MP3/DVD/CD players. The advanced current-limited control scheme provides high-efficiency over a wide range of output loads. The highly-efficient operation (up to 100% duty cycle) allows extremely low dropout voltage, increasing the usable supply voltage range. In no-load conditions the AS1341 draws only 12µA; in shutdown mode it draws only 0.8µA to further reduce power consumption and extend battery life. The AS1341 features an integrated 20V switching MOSFET, internal current sensing, and a high switching frequency, for minimal PCB space and external component requirements. Figure 21. AS1341 - Block Diagram - 5V fixed Output Voltage 3 + +– – 5 IN CIN – + 4 LX 8 POK RPULL L1 AS1341 7 SHDNN S 6 ILIMIT Current Limit Control Maximum OnTime Delay Minimum OffTime Delay – + VSET 1.25V + – Q R + – + – OUT 1 FB D1 + COUT 100mV 2 GND Current-Limit Control The AS1341 uses a proprietary current-limiting control scheme with operation up to 100% duty cycle. The DC-DC converter pulses as needed to maintain regulation, resulting in a variable switching frequency that increases with the load. This eliminates the high-supply currents associated with conventional constant-frequency pulse-width-modulation (PWM) controllers that unnecessarily switch the MOSFET. When the output voltage is too low, the error comparator sets a flip-flop, which turns on the internal P-channel MOSFET and begins a switching cycle. The inductor current ramps up linearly, storing energy in a magnetic field while charging the output capacitor and servicing the load (see Figure 19 on page 7). The MOSFET turns off when the peak current limit is reached, or when the maximum on-time of 10µs is exceeded and the output voltage is in regulation. If the output is out of regulation and the peak current is never reached, the MOSFET remains on, allowing a duty cycle up to 100%. This feature ensures the lowest possible dropout voltage. Once the MOSFET turns off, the flip-flop resets, the inductor current is pulled through D1 (see Figure 21), and the current through the inductor ramps back down, transferring the stored energy to the output capacitor and load. The MOSFET remains off until the 0.4µs minimum off-time expires, and the output voltage goes out of regulation. www.austriamicrosystems.com Revision 1.05 8 - 17 AS1341 Datasheet - D e t a i l e d D e s c r i p t i o n Dropout Voltage A buck converter’s minimum input-to-output voltage differential (dropout voltage) determines the lowest usable supply voltage. In battery-powered systems, this limits the useful end-of-life battery voltage. To maximize battery life, the AS1341 operates with duty cycles up to 100%, which minimizes the dropout voltage and eliminates switching losses while in dropout. When the supply voltage approaches the output voltage, the P-channel MOSFET remains on continuously to supply the load. Note: Dropout voltage is defined as the difference between the input and output voltages when the input is low enough for the output to drop out of regulation. For a step-down converter with 100% duty cycle, dropout is related to the MOSFET drain-to-source on-resistance (RDSON) and inductor series resistance (RINDUCTOR), and thus it is proportional to the load current: VDROPOUT = IOUT x (RDSON + RINDUCTOR) (EQ 1) Shutdown A logic low on pin SHDNN shuts down the AS1341; a logic high on SHDNN powers on the device. In shutdown mode the supply current drops to 0.8µA to maximize battery life, and the internal P-channel MOSFET turns off to isolate the output from the input. The output capacitance and load current determine the output voltage decay rate. Note: Pin SHDNN should not be left floating. If the shutdown feature is not used, connect SHDNN to IN. Power-OK Output The AS1341 provides a Power OK output (POK) that goes high-impedance when the output reaches 92.5% of its regulation point. POK goes low when the output is below 92.5% of the regulation point and the AS1341 is turned on (IN ≥ 4.5V and SHDNN ≥ 2.4V). A 12kΩ to 1MΩ pullup resistor between pin POK and pin IN or pin OUT or another voltage (≤ IN) can provide a microprocessor logic control signal. Note: Connect pin POK to GND when the Power-Ok feature is not used. Thermal-Overload Protection Integrated thermal-overload protection limits total power dissipation in the AS1341. During continuous thermal-overload conditions, when the AS1341 junction temperature exceeds TJ = +145ºC, the internal thermal sensor turns off the pass transistor, allowing the AS1341 to cool down. When the AS1341 junction temperature cools by 10ºC, the thermal sensor turns the pass transistor on again resulting in a pulsed output. www.austriamicrosystems.com Revision 1.05 9 - 17 AS1341 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 Adjusting Output Voltage The AS1341 feedback input features dual-mode operation. Connect FB to GND for the 5.0V preset output voltage (see Figure 21 on page 8). Adjust the output voltage by connecting a voltage-divider from the output to GND (see Figure 22). Figure 22. Adjustable Output Voltage Circuit VIN 4.5V to 20V L1 5 IN 4 LX D1 1.25V to VIN CIN 7 SHDNN 6 ILIMIT + RPULL COUT AS1341 3 POK 1 FB R1 2 GND 8 OUT R2 Indicates High-Power Trace Select a value for R2 between 10k and 1MΩ. Calculate R1 as: V OUT R 1 = R 2 ⋅ ⎛ -------------- – 1⎞ ⎝ V FB ⎠ Where: VFB = 1.25V. VOUT may range from 1.25V to VIN. (EQ 2) Negative Output Voltage VIN may range from 4.5V to (20V-VOUT). Therefore the maximum negative output voltage is -15V. Figure 23. Adjustable Negative Output Voltage Circuit VIN 4.5V to (20V-VOUT) 5 IN 7 SHDNN 6 CIN ILIMIT 2 GND 4 LX 3 D1 R1 + COUT R2 L1 AS1341 POK 1 FB 8 OUT VOUT = -1.25V to -15V Indicates High-Power Trace www.austriamicrosystems.com Revision 1.05 10 - 17 AS1341 Datasheet - A p p l i c a t i o n I n f o r m a t i o n Setting Current Limit The AS1341 adjustable peak current limit is set by connecting ILIMIT as shown in Table 4. Table 4. Setting Peak Current Limit Current Limit 700mA 1400mA ILIMIT Connected To GND IN The current limit chosen should reflect the maximum load current. The maximum output current is half of the peak current limit. Choosing a lower current limit allows using an inductor with a lower current rating, however, it requires a higher inductance (see Inductor Selection) and does not allow for reduced inductor package size. Inductor Selection The AS1341 operates with a wide range of inductance values. For most applications, values between 10µH and 47µH work best with the controller’s high switching frequency. Larger inductor values will reduce the switching frequency and thereby improve efficiency and EMI. Note: The four key factors in inductor selection are inductance value, saturation rating, series resistance, and size. The trade-off for improved efficiency is a higher output ripple and slower transient response. On the other hand, lowvalue inductors respond faster to transients, improve output ripple, offer smaller physical size, and minimize cost. If the inductor value is too small, the peak inductor current exceeds the current limit due to current-sense comparator propagation delay, potentially exceeding the inductor’s current rating. Calculate the minimum inductance value as follows: LMIN = ((VINMAX - VOUTPUT) x tONMIN/ILXPEAK Where: tONMIN = 1µs The inductor saturation current rating must be greater than the peak switch current limit, plus the overshoot due to the 250ns current-sense comparator propagation delay. Saturation occurs when the magnetic flux density of the inductor reaches the maximum level the core can support and the inductance starts to fall. Choose an inductor with a saturation rating greater than IPEAK in the following equation: IPEAK = (ILXPEAK + (VIN - VOUTPUT) x 250ns)/L (EQ 4) (EQ 3) Inductor series resistance affects both efficiency and dropout voltage (see Dropout Voltage on page 9). High series resistance limits the maximum current available at lower input voltages, and increases the dropout voltage. For optimum performance, select an inductor with the lowest possible DC resistance that fits in the allotted dimensions. Table 5. Recommended Inductors Part Number MSS6132-103ML LPS4018-472ML MSS6132-393ML LPS4018-223ML CDRH6D28NP-150 CDRH5D18NP-4R1 CDRH6D28NP-470 CDRH5D18NP-220 LQH66SN-100M03 LQH55DN-150M03 LQH66SN-470M03 LQH55DN-470M03 L 10µH 4.7µH 39µH 22µH 15µH 4.1µH 47µH 22µH 10µH 15µH 47µH 47µH DCR 85mΩ 125mΩ 345mΩ 360mΩ 62mΩ 57mΩ 176mΩ 215mΩ 36mΩ 150mΩ 170mΩ 400mΩ Current Rating 1.4A 1.8A 0.8A 0.7A 1.4A 1.95A 0.8A 0.8A 1.6A 1.4A 0.8A 0.8A Murata www.murata.com Sumida www.sumida.com Manufacturer Coilcraft www.coilcraft.com www.austriamicrosystems.com Revision 1.05 11 - 17 AS1341 Datasheet - A p p l i c a t i o n I n f o r m a t i o n Maximum Output Current The AS1341 output current determines the regulator’s switching frequency. When the converter approaches continuous mode, the output voltage falls out of regulation. For the typical application, the maximum output current is approximately: ILOADMAX = 1/2 x ILXPEAKMIN For low-input voltages, the maximum on-time may be reached and the load current is limited by: ILOAD = (1/2 x (VIN - VOUT) x 10µs)/L (EQ 6) (EQ 5) Output Capacitor Choose the output capacitor to service the maximum load current with acceptable voltage ripple. The output ripple has two components: variations in the charge stored in the output capacitor with each LX pulse, and the voltage drop across the capacitor’s equivalent series resistance (ESR) caused by the current into and out of the capacitor: VRIPPLE ≅ VRIPPLEESR + VRIPPLEC The output voltage ripple as a consequence of the ESR and output capacitance is: VRIPPLEESR = ESR x IPEAK VRIPPLEC = (L x (IPEAK - IOUTPUT)2)/(2 x (COUT x VOUTPUT)) x VIN/(VIN - VOUTPUT) Where: IPEAK is the peak inductor current (see Inductor Selection on page 11). The worst-case ripple occurs at no-load. Equations EQ 7, EQ 8, and EQ 9 are suitable for initial capacitor selection, but actual values should be set by testing a prototype or evaluation circuit. As a general rule, a smaller amount of charge delivered in each pulse results in less output ripple. Since the amount of charge delivered in each oscillator pulse is determined by the inductor value and input voltage, the voltage ripple increases with larger inductance, and as the input voltage decreases. Table 6. Recommended Output Capacitor Part Number T520V107M010ATE018 A700V826M006ATE018 T520B107M006ATE040 T520A336M006ATE070 A700V226M006ATE028 510X107M020ATE040 EEFUD0J101R EEFCD0K330R 10TPB100ML 6TPB47M C 100µF 82µF 100µF 33µF 22µF 10µF 100µF 33µF 100µF 47µF ESR 18mΩ 18mΩ 40mΩ 70mΩ 28mΩ 40mΩ 15mΩ 18mΩ 55mΩ 70mΩ Rated Voltage 10V 6.3V 6V 6.3V 6.3V 20V 6.3V 8V 10V 6.3V Panasonic www.panasonic.com Sanyo www.edc.sanyo.com Manufacturer Kemet www.kemet.com (EQ 8) (EQ 9) (EQ 7) www.austriamicrosystems.com Revision 1.05 12 - 17 AS1341 Datasheet - A p p l i c a t i o n I n f o r m a t i o n Input Capacitor The input filter capacitor reduces peak currents drawn from the power source and reduces noise and voltage ripple on the input caused by the circuit’s switching. The input capacitor must meet the ripple-current requirement (IRMS) imposed by the switching current defined as: IRMS = (ILOAD x VOUTPUT)/VIN x √((4/3) x (VIN - VOUTPUT) - 1) (EQ 10) For most applications, non-tantalum type (ceramic, aluminum, polymer, or OS-CON) are preferred due to their robustness to high in-rush currents typical of systems with low-impedance battery inputs. Alternatively, connect two (or more) smaller value low-ESR capacitors in parallel to reduce cost. Choose an input capacitor that exhibits less than +10ºC temperature rise at the RMS input current for optimal circuit life. Table 7. Recommended Input Capacitor C TC Code Rated Voltage Manufacturer Murata www.murata.com Taiyo Yuden www.t-yuden.com Kemet www.kemet.com Panasonic www.panasonic.com Sanyo www.edc.sanyo.com 10µF X7R 25V Diode Selection The current in the D1 (see Figure 22 on page 10) changes abruptly from zero to its peak value each time the LX switch turns off. To avoid excessive losses, the diode must have a fast turn-on time and a low forward voltage. Note: Ensure that the diode peak current rating exceeds the peak current limit set by the current limit (see Setting Current Limit on page 11), and that its breakdown voltage exceeds VIN. Schottky diodes are recommended. Stable Operation A well-designed system and selection of high-quality external components can eliminate excessive noise on pins OUT, FB, or GND, which can lead to unstable device operation. Instability typically manifests itself as grouped switching pulses with large gaps and excessive low-frequency output ripple (motorboating) during no-load or light-load conditions. Recommended Components Table 8. Recommended Components Input Voltage 4.5V to 20V 1.25V to 5V 4.5v to 12V High Output Voltage ILIMIT Inductor MSS6132-103ML LQH66SN-100M03 LQH55DN-150M03 CDRH6D28NP-150 CDRH5D18NP-4R1 LPS4018-472ML MSS6132-393ML CDRH6D28NP-470 LQH66SN-470M03 LQH55DN-470M03 MSS6132-103ML LPS4018-223ML CDRH5D18NP-220 5V to VIN High or Low See Inductors above Output Capacitor T520V107M010ATE018 A700V826M006ATE018 T520B107M006ATE040 EEFUD0J101R 10TPB100ML 4.5V to 20V 1.25V to 5V 4.5V to 12V 6V to 20V Low EEFCD0K330R 6TPB47M T520A336M006ATE070 A700V226M006ATE028 510X107M020ATE040 www.austriamicrosystems.com Revision 1.05 13 - 17 AS1341 Datasheet - A p p l i c a t i o n I n f o r m a t i o n PC Board Layout and Grounding High switching frequencies and large peak currents make PC board layout an important part of AS1341-based designs. Good PCB layout can avoid switching noise being introduced into the feedback path, resulting in jitter, instability, or degraded performance. - High-power traces (see Figure 22 on page 10) should be as short and wide as possible. - The current loops formed by the external components (CIN, COUT, L1, and D1 see Figure 22 on page 10) should be as short as possible to avoid radiated noise. Connect the ground pins of these power components at a common node in a star-ground configuration. - Separate noisy traces, such as the LX node, from the feedback network with grounded copper. - Keep the extra copper on the PCB and integrate it into a pseudo-ground plane. - When using external feedback, place the resistors as close to pin FB as possible to minimize noise coupling. www.austriamicrosystems.com Revision 1.05 14 - 17 AS1341 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 devices are available in a TDFN-8 3x3mm package. Figure 24. TDFN-8 3x3mm Package D D2 SEE DETAIL B B A L E2/2 aaa C 2x PIN 1 INDEX AREA (D/2 xE/2) D2/2 E2 K N N-1 e (ND-1) X e BTM VIEW E PIN 1 INDEX AREA (D/2 xE/2) aaa C 2x TOP VIEW b ddd bbb C CAB e DETAIL B e/2 Terminal Tip ccc C A3 C SEATING PLANE 0.08 C A Datum A or B EVEN TERMINAL SIDE Symbol A A1 A3 L1 L2 aaa bbb ccc ddd eee ggg Notes: Min 0.70 0.00 0.03 Typ 0.75 0.02 0.20 REF Max 0.80 0.05 0.15 0.13 0.15 0.10 0.10 0.05 0.08 0.10 Notes 1, 2 1, 2 1, 2 1, 2 1, 2 1, 2 1, 2 1, 2 1, 2 1, 2 1, 2 Symbol D BSC E BSC D2 E2 L θ K b e N ND Min Typ 3.00 3.00 A1 SIDE VIEW Max 1.60 1.35 0.30 0º 0.20 0.18 0.40 2.50 1.75 0.50 14º 0.30 0.25 0.65 8 4 Notes 1, 2 1, 2 1, 2 1, 2 1, 2 1, 2 1, 2 1, 2, 5 1, 2 1, 2, 5 1. Figure 24 is shown for illustration only. 2. All dimensions are in millimeters; angles in degrees. 3. Dimensioning and tolerancing conform to ASME Y14.5 M-1994. 4. N is the total number of terminals. 5. The terminal #1 identifier and terminal numbering convention shall conform to JEDEC 95-1, SPP-012. Details of terminal #1 identifier are optional, but must be located within the zone indicated. The terminal #1 identifier may be either a mold or marked feature. 6. Dimension b applies to metallized terminal and is measured between 0.15mm and 0.30mm from the terminal tip. 7. ND refers to the maximum number of terminals on side D. 8. Unilateral coplanarity zone applies to the exposed heat sink slug as well as the terminals www.austriamicrosystems.com Revision 1.05 15 - 17 AS1341 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 shown in Table 9. Table 9. Ordering Information Ordering Code AS1341-BTDT Description 20V, 600mA, 100% Duty Cycle, Step-Down Converter Delivery Form Tape and Reel Package TDFN-8 3x3mm Note: All products are RoHS compliant and Pb-free. Buy our products or get free samples online at ICdirect: http://www.austriamicrosystems.com/ICdirect For further information and requests, please contact us mailto:sales@austriamicrosystems.com or find your local distributor at http://www.austriamicrosystems.com/distributor www.austriamicrosystems.com Revision 1.05 16 - 17 AS1341 Datasheet Copyrights Copyright © 1997-2009, austriamicrosystems 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 austriamicrosystems AG are covered by the warranty and patent indemnification provisions appearing in its Term of Sale. austriamicrosystems 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. austriamicrosystems 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 austriamicrosystems 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 austriamicrosystems AG for each application. For shipments of less than 100 parts the manufacturing flow might show deviations from the standard production flow, such as test flow or test location. The information furnished here by austriamicrosystems AG is believed to be correct and accurate. However, austriamicrosystems AG shall not be liable to recipient or any third party for any damages, including but not limited to personal injury, property damage, loss of profits, loss of use, interruption of business or indirect, special, incidental or consequential damages, of any kind, in connection with or arising out of the furnishing, performance or use of the technical data herein. No obligation or liability to recipient or any third party shall arise or flow out of austriamicrosystems AG rendering of technical or other services. Contact Information Headquarters austriamicrosystems 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.austriamicrosystems.com/contact www.austriamicrosystems.com Revision 1.05 17 - 17