austriamicrosystems AG is now ams AG The technical content of this austriamicrosystems datasheet is still valid. Contact information: Headquarters: ams AG Tobelbaderstrasse 30 8141 Unterpremstaetten, Austria Tel: +43 (0) 3136 500 0 e-Mail: [email protected] Please visit our website at www.ams.com Datasheet AS1310 U l t r a L o w Q u i e s c e n t C u r r e n t , H y s te r e t i c D C - D C S t e p - U p C o n v e r t e r 1 General Description 2 Key Features Fixed output voltage range: 1.8V to 3.3V al id Input voltage range: 0.7V to 3.6V The AS1310 is an ultra low IQ hysteretic step-up DC-DC converter optimized for light loads (60mA), where it achieves efficiencies of up to 92%. Output current: 60mA @ VIN=0.9V, VOUT=1.8V AS1310 operates from a 0.7V to 3.6V supply and supports output voltages between 1.8V and 3.3V. Besides the available AS1310 standard variants any variant with output voltages in 50mV steps are available. See Ordering Information on page 18 for more information. Quiescent current: 1µA (typ.) Up to 92% efficiency If the input voltage exceeds the output voltage the device is in a feed-through mode and the input is directly connected to the output voltage. lv Shutdown current: < 100nA Output disconnect in shutdown Feedthrough mode when VIN > VOUT Adjustable low battery detection In order to save power the AS1310 features a shutdown mode, where it draws less than 100nA. During shutdown mode the battery is disconnected from the output. TDFN (2x2) 8-pin package am lc s on A te G nt st il In light load operation, the device enters a sleep mode when most of the internal operating blocks are turned off in order to save power. This mode is active approximately 50µs after a current pulse provided that the output is in regulation. No external diode or transistor required Over temperature protection 3 Applications The AS1310 also offers adjustable low battery detection. If the battery voltage decreases below the threshold defined by two external resistors on pin LBI, the LBO output is pulled to logic low. The AS1310 is an ideal solution for single and dual cell powered devices as blood glucose meters, remote controls, hearing aids, wireless mouse or any light-load application. The AS1310 is available in a TDFN (2x2) 8-pin package. Figure 1. AS1310 Typical Application Diagram R1 LX R2 On Off 1 LBI LBO AS1310 R3 VOUT 1.8V to 3.3V 4 VOUT C2 22µF 5 7 REF EN www.austriamicrosystems.com/DC-DC_Step-Up/AS1310 Low Battery Detect 6 VIN Te ch C1 22µF 3 8 ni VIN 0.7V to 3.6V ca L1 6.8µH 2 CREF 100nF GND Revision 1.8 1 - 19 AS1310 Datasheet - P i n A s s i g n m e n t s 4 Pin Assignments 1 8 VIN GND 2 7 EN 6 LBO 5 REF AS1310 3 VOUT 4 Exposed pad am lc s on A te G nt st il LX lv LBI al id Figure 2. Pin Assignments (Top View) 4.1 Pin Descriptions Table 1. Pin Descriptions Pin Number Pin Name Description 1 LBI Low Battery Comparator Input. 0.6V Threshold. May not be left floating. If connected to GND, LBO is working as Power Output OK. 2 GND Ground 3 LX 4 VOUT 5 REF Reference Pin. Connect a 100nF ceramic capacitor to this pin. 6 LBO Low Battery Comparator Output. Open-drain output. 7 EN Enable Pin. Logic controlled shutdown input. 1 = Normal operation; 0 = Shutdown; shutdown current <100nA. VIN Battery Voltage Input. Decouple VIN with a 22µF ceramic capacitor as close as possible to VIN and GND. NC Exposed Pad. This pad is not connected internally. Can be left floating or connect to GND to achieve an optimal thermal performance. ca Output Voltage. Decouple VOUT with a ceramic capacitor as close as possible to VOUT and GND. ni ch 8 External Inductor Connector. Te 9 www.austriamicrosystems.com/DC-DC_Step-Up/AS1310 Revision 1.8 2 - 19 AS1310 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 Min Max Units Electrical Parameters Comments al id Parameter -0.3 +5 V LX, REF to GND -0.3 VOUT + 0.3 V Input Current (latch-up immunity) -100 100 mA Norm: JEDEC 78 ±2 kV Norm: MIL 883 E method 3015 58 ºC/W Electrostatic Discharge Electrostatic Discharge HBM Temperature Ranges and Storage Conditions am lc s on A te G nt st il Thermal Resistance θJA lv VIN, VOUT, EN, LBI, LBO to GND Junction Temperature Storage Temperature Range -55 Package Body Temperature Humidity non-condensing 5 ºC +125 ºC +260 ºC 85 % 1 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 a maximum floor life time of unlimited Te ch ni ca Moisture Sensitive Level +125 www.austriamicrosystems.com/DC-DC_Step-Up/AS1310 Revision 1.8 3 - 19 AS1310 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 All limits are guaranteed. The parameters with Min and Max values are guaranteed by production tests or SQC (Statistical Quality Control) methods. VIN = 1.5V, C1 = C2 = 22µF, CREF = 100nF, Typical values are at TAMB = +25ºC (unless otherwise specified). All limits are guaranteed. The parameters with min and max values are guaranteed with production tests or SQC (Statistical Quality Control) methods. Symbol Parameter Conditions Min TAMB Operating Temperature Range -40 Input Voltage Range 0.7 Typ Input Minimum Startup Voltage ILOAD = 1mA, TAMB = +25°C 0.7 Regulation Output Voltage Range 1.8 Output Voltage Tolerance VOUT Lockout Threshold Operating Current 3.6 V 0.8 V 3.3 V 1 +2 % ILOAD = 10mA -3 +3 % Rising Edge 1.55 1.75 V 100 nA 1.2 µA 100 nA Quiescent Current VOUT VOUT = 1.02xVON, REF = 0.99xVON, No load, TAMB = +25°C Shutdown Current TAMB = +25ºC NMOS RON 0.8 VOUT = 3V PMOS 1.65 1 0.35 Ω 0.5 Ω 3.6 4.2 4.8 µs Peak Current Limit 320 400 480 mA Zero Crossing Current 5 20 35 mA Enable, Reference ca NMOS maximum On-time IPEAK EN Input Voltage High VENL EN Input Voltage Low ni VENH 0.7 V 0.1 V EN Input Bias Current EN = 3.6V, TAMB = +25°C 100 nA REF Input Bias Current REF = 0.99xVOUTNOM, TAMB = +25°C 100 nA 0.63 V ch IREF °C -2 VOUT = 1.02xVOUTNOM, REF = 0.99xVOUTNOM, TAMB = +25°C Switches IEN +85 ILOAD = 10 mA, TAMB = +25°C Quiescent Current VIN IQ ISHDN Units am lc s on A te G nt st il VOUT Max lv VIN al id Table 3. Electrical Characteristics Low Battery & Power-OK Te VLBI LBI Threshold Falling Edge 0.57 LBI Hysteresis 0.6 25 ILBI LBI Leakage Current VLBO LBO Voltage Low ILBO = 1mA ILBO LBO Leakage Current LBO = 3.6V, TAMB = +25°C Power-OK Threshold LBI = 0V, Falling Edge 2 www.austriamicrosystems.com/DC-DC_Step-Up/AS1310 LBI = 3.6V, TAMB = +25°C Revision 1.8 20 90 92.5 mV 100 nA 100 mV 100 nA 95 % 4 - 19 AS1310 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 Table 3. Electrical Characteristics Symbol Parameter Conditions Thermal Shutdown 10°C Hysteresis Min Typ Max Units Thermal Protection 150 °C Te ch ni ca am lc s on A te G nt st il lv al id 1. The regulator is in startup mode until this voltage is reached. Caution: Do not apply full load current until the device output > 1.75V 2. LBO goes low in startup mode as well as during normal operation if: - The voltage at the LBI pin is below LBI threshold. - The voltage at the LBI pin is below 0.1V and VOUT is below 92.5% of its nominal value. www.austriamicrosystems.com/DC-DC_Step-Up/AS1310 Revision 1.8 5 - 19 AS1310 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 TAMB = +25°C, unless otherwise specified. Figure 3. Efficiency vs. Output Current; VOUT = 1.8V 80 75 75 70 65 60 55 50 al id 80 70 65 60 55 50 Vin = 0.9V Vin = 0.9V Vin = 1.2V am lc s on A te G nt st il Vin = 1.2V 45 45 Vin = 1.5V 40 0.01 L1: XPL7030-682M 85 Efficiency (%) Efficiency (%) 90 L1: XPL2010-682M 85 lv 90 Figure 4. Efficiency vs. Output Current; VOUT = 1.8V 0.1 1 10 100 Vin = 1.5V 40 0.01 1000 0.1 Output Current (mA) Figure 5. Efficiency vs. Output Current; VOUT = 3.0V 95 Efficiency (%) 100 L1: XPL2010-682M 90 75 70 65 60 Vin = 1.2V Vin = 1.8V ca 0.1 1 10 100 75 70 65 60 Vin = 0.9V Vin = 1.2V Vin = 1.5V Vin = 1.8V 45 Vin = 2.4V 40 0.01 85 80 55 50 Vin = 1.5V 45 40 0.01 1000 Vin = 2.4V 0.1 Output Current (mA) 100 1000 ni 180 ch 160 Output Current (mA) . 90 85 Te 80 75 70 65 Iout = 1mA Iout =10mA 55 10 Figure 8. Maximum Output Current vs. Input Voltage L1: XPL2010-682M 60 1 Output Current (mA) Figure 7. Efficiency vs. Input Voltage; VOUT = 1.8V Efficiency (%) 1000 L1: XPL7030-682M 95 Vin = 0.9V 55 50 95 100 90 85 80 100 10 Figure 6. Efficiency vs. Output Current; VOUT = 3.0V Efficiency (%) 100 1 Output Current (mA) 140 120 100 80 60 40 Vout = 1.8V 20 Vout = 3.0V Iout =50mA 50 0 0.7 0.9 1.1 1.3 1.5 1.7 0 1.9 Input Voltage (V) www.austriamicrosystems.com/DC-DC_Step-Up/AS1310 0.5 1 1.5 2 2.5 3 Input Voltage (V) Revision 1.8 6 - 19 AS1310 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 10. RON vs. Temperature 1 1 0.95 0.9 0.9 0.8 0.85 0.7 0.8 0.6 R ON (Ω) 0.5 0.7 al id 0.75 0.4 0.65 0.3 0.6 0.2 0.55 0.1 0.5 0 1 2 3 4 5 6 7 8 9 10 0 -40 NM OS -15 10 35 60 85 Temperature (°C) am lc s on A te G nt st il Output Current (mA) PM OS lv Start-up Voltage (V) Figure 9. Start-up Voltage vs. Output Current 100mV/Div VOUT (AC) ILX 200mA/Div VLX 2V/Div Figure 11. Output Voltage Ripple; VIN = 2V, VOUT = 3V, Rload = 100Ω Te ch ni ca 5µs/Div www.austriamicrosystems.com/DC-DC_Step-Up/AS1310 Revision 1.8 7 - 19 AS1310 Datasheet - D e t a i l e d D e s c r i p t i o n 8 Detailed Description 8.1 Hysteretic Boost Converter Hysteretic boost converters are so called because comparators are the active elements used to determine on-off timing via current and voltage measurements. There is no continuously operating fixed oscillator, providing an independent timing reference. As a result, a hysteretic or comparator based converter has a very low quiescent current. In addition, because there is no fixed timing reference, the operating frequency is determined by external component (inductor and capacitors) and also the loading on the output. al id Ripple at the output is an essential operating component. A power cycle is initiated when the output regulated voltage drops below the nominal value of VOUT (0.99 x VOUT). Inductor current is monitored by the control loop, ensuring that operation is always dis-continuous. 8.1.1 lv The application circuit shown in Figure 1 will support many requirements. However, further optimization may be useful, and the following is offered as a guide to changing the passive components to more closely match the end requirement. Input Loop Timing am lc s on A te G nt st il The input loop consists of the source dc supply, the input capacitor, the main inductor, and the N-channel power switch. The on timing of the Nchannel switch is determined by a peak current measurement or a maximum on time. In the AS1310, peak current is 400mA (typ) and maximum on time is 4.2µs (typ). Peak current measurement ensures that the on time varies as the input voltage varies. This imparts line regulation to the converter. The fixed on-time measurement is something of a safety feature to ensure that the power switch is never permanently on. The fixed on-time is independent of input voltage changes. As a result, no line regulation exists. Figure 12. Simplified Boost DCDC Architecture L1 SW2 VIN VOUT Q CIN SW1 Q FB COUT RLOAD IPK GND 0V ni ca 0V On time of the power switch (Faraday’s Law) is given by: ch LI PK T ON = ------------------------------------------------------------------ sec [volts, amps, ohms, Henry] V IN – ( I PK R SW1 + I PK R L1 ) (EQ 1) Te Applying Min and Max values and neglecting the resistive voltage drop across L1 and SW1; TON _ MIN = TON _ MAX = www.austriamicrosystems.com/DC-DC_Step-Up/AS1310 LMIN I PK _ MIN V IN _ MAX (EQ 2) LMAX I PK _ MAX V IN _ MIN (EQ 3) Revision 1.8 8 - 19 AS1310 Datasheet - D e t a i l e d D e s c r i p t i o n Figure 13. Simplified Voltage and Current Waveforms V 0.99VOUT_NOM al id VOUT Ripple VOUT B B VIN VIND_TON C D A C D lv VIND_TOFF T am lc s on A te G nt st il 0 TOFF TWAIT IL TON SW1_on SW2_off TOFF TWAIT IPK 0 SW2_on SW1_off T T T Another important relationship is the “volt-seconds” law. Expressed as following: ca V ON T ON = V OFF T OFF (EQ 4) ni Voltages are those measured across the inductor during each time segment. Figure 13 shows this graphically with the shaded segments marked “A & B”. Re-arranging (EQ 4): V OUT – V IN T ON ------------ = ---------------------------V IN T OFF (EQ 5) ch The time segment called TWAIT in Figure 13 is a measure of the “hold-up” time of the output capacitor. While the output voltage is above the threshold (0.99xVOUT), the output is assumed to be in regulation and no further switching occurs. 8.1.2 Inductor Choice Example Te For the AS1310 VIN_MIN = 0.9V, VOUT_MAX = 3.3V, (EQ 5) gives Ton=2.66TOFF. Let the maximum operating on-time = 1µs. Note that this is shorter than the minimum limit on-time of 3.6µs. Therefore from (EQ 5), TOFF = 0.376µs. Using (EQ 3), LMAX is obtained: LMAX = 1.875µH. The nearest preferred value is 2.2µH. This value provides the maximum energy storage for the chosen fixed on-time limit at the minimum VIN. www.austriamicrosystems.com/DC-DC_Step-Up/AS1310 Revision 1.8 9 - 19 AS1310 Datasheet - D e t a i l e d D e s c r i p t i o n Energy stored during the on time is given by: E = 0.5L ( I PK ) 2 Joules (Region A in Figure 13) (EQ 6) If the overall time period (TON + TOFF) is T, the power taken from the input is: 2 0.5L ( I PK ) P IN = --------------------------- Watts T (EQ 7) al id Assume output power is 0.8 PIN to establish an initial value of operating period T. TWAIT is determined by the time taken for the output voltage to fall to 0.99xVOUT. The longer the wait time, the lower will be the supply current of the converter. Longer wait times require increased output capacitance. Choose TWAIT = 10% T as a minimum starting point for maximum energy transfer. For very low power load applications, choose TWAIT ≥ 50% T. Output Loop Timing lv 8.1.3 am lc s on A te G nt st il The output loop consists of the main inductor, P-channel synchronous switch (or diode if fitted), output capacitor and load. When the input loop is interrupted, the voltage on the LX pin rises (Lenz’s Law). At the same time a comparator enables the synchronous switch, and energy stored in the inductor is transferred to the output capacitor and load. Inductor peak current supports the load and replenishes the charge lost from the output capacitor. The magnitude of the current from the inductor is monitored, and as it approaches zero, the synchronous switch is turned off. No switching action continues until the output voltage falls below the output reference point (0.99 x VOUT). Output power is composed of the dc component (Region C in Figure 13): I PK T OFF PREGION_C = V IN -------- ------------2 T (EQ 8) Output power is also composed of the inductor component (Region B in Figure 13), neglecting efficiency loss: 2 0.5L ( I PK ) PREGION_B = --------------------------T (EQ 9) Total power delivered to the load is the sum of (EQ 8) and (EQ 9): 2 P TOTAL I PK T OFF 0.5L ( I PK ) = V IN -------- ------------- + --------------------------2 T T (EQ 10) From (EQ 3) (using nominal values) peak current is given by: T ON V IN I PK = ------------------L (EQ 11) Substituting (EQ 11) into (EQ 10) and re-arranging: 2 ca V IN T ON P TOTAL = ---------------------- ( 0.9T ) 2TL (EQ 12) 0.9T incorporates a wait time TWAIT = 10% T ch ni Output power in terms of regulated output voltage and load resistance is: 2 V OUT P OUT = ----------------R LOAD (EQ 13) Te Combining (EQ 12) and (EQ 13): 2 2 V IN T ON V OUT - ( 0.9T )η ---------------- = --------------------R LOAD 2TL (EQ 14) Symbol η reflects total energy loss between input and output and is approximately 0.8 for these calculations. Use (EQ 14) to plot duty cycle (TON/T) changes for various output loadings and changes to VIN. www.austriamicrosystems.com/DC-DC_Step-Up/AS1310 Revision 1.8 10 - 19 AS1310 Datasheet - D e t a i l e d D e s c r i p t i o n 8.1.4 Input Capacitor Selection The input capacitor supports the triangular current during the on-time of the power switch, and maintains a broadly constant input voltage during this time. The capacitance value is obtained from choosing a ripple voltage during the on-time of the power switch. Additionally, ripple voltage is generated by the equivalent series resistance (ESR) of the capacitor. For worst case, use maximum peak current values from the datasheet. I PEAK T ON C IN = ------------------------V RIPPLE CIN = 9.6µF Nearest preferred would be 10µF. V PK _ RIPPLE _ ESR = I PK R ESR al id Using TON = 1µs, and IPEAK = 480mA, and VRIPPLE = 50mV, EQ 15 yields: (EQ 15) (EQ 16) lv Typically, the ripple due to ESR is not dominant. ESR for the recommended capacitors (Murata GMR), ESR = 5mΩ to 10mΩ. For the AS1310, maximum peak current is 480mA. Ripple due to ESR is 2.4mV to 4.8mV. 8.1.5 am lc s on A te G nt st il Ripple at the input propagates through the common supply connections, and if too high in value can cause problems elsewhere in the system. The input capacitance is an important component to get right. Output Capacitor Selection The output capacitor supports the triangular current during the off-time of the power switch (inductor discharge period), and also the load current during the wait time (Region D in Figure 13) and on-time (Region A in Figure 13) of the power switch. COUT = I LOAD (TON + TWAIT ) (1 − 0.99)VOUT _ NOM (EQ 17) Note: There is also a ripple component due to the equivalent series resistance (ESR) of the capacitor. 8.2 Summary User Application Defines: VINmin, VINmax, VOUTmin, VOUTmax, ILOADmin, ILOADmax Inductor Selection: Select Max on-time = 0.5µs to 3µs for AS1310. Use (EQ 3) to calculate inductor value. Use (EQ 5) to determine off-time. Use (EQ 6) to check that power delivery matches load requirements assume 70% conversion efficiency. ca Use (EQ 13) to find overall timing period value of T at min VIN and max VOUT for maximum load conditions. Input Capacitor Selection: Choose a ripple value and use (EQ 14) to find the value. Te ch ni Output Capacitor Selection: Determine TWAIT via (EQ 6) or (EQ 13), and use (EQ 16) to find the value. www.austriamicrosystems.com/DC-DC_Step-Up/AS1310 Revision 1.8 11 - 19 AS1310 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 AS1310 is available with fixed output voltages from 1.8V to 3.3V in 50mV steps. 6.8µH LX CIN 22µF 1.8V to 3.3V Output Zero Crossing Detector Startup Circuitry Driver and Control Logic VIN VOUT COUT 22µF lv 0.7 to 3.6V Input al id Figure 14. AS1310 Block Diagram R3 – am lc s on A te G nt st il + LBI LBO Imax Detection EN AS1310 VREF REF CREF 100nF GND 9.1 AS1310 Features Shutdown. The part is in shutdown mode while the voltage at pin EN is below 0.1V and is active when the voltage is higher than 0.7V. Note: EN can be driven above VIN or VOUT, as long as it is limited to less than 3.6V. ca Output Disconnect and Inrush Limiting. During shutdown VOUT is going to 0V and no current from the input source is running through the device. This is true as long as the input voltage is higher than the output voltage. Feedthrough Mode. If the input voltage is higher than the output voltage the supply voltage is connected to the load through the device. To guarantee a proper function of the AS1310 it is not allowed that the supply exceeds the maximum allowed input voltage (3.6V). Te ch ni In this feedthrough mode the quiescent current is 35µA (typ.). The device goes back into step-up mode when the oputput voltage is 4% (typ.) below VOUTNOM. www.austriamicrosystems.com/DC-DC_Step-Up/AS1310 Revision 1.8 12 - 19 AS1310 Datasheet - A p p l i c a t i o n I n f o r m a t i o n 9.1.1 Power-OK and Low-Battery-Detect Functionality LBO goes low in startup mode as well as during normal operation if: - The voltage at the LBI pin is below LBI threshold (0.6V). This can be used to monitor the battery voltage. - LBI pin is connected to GND and VOUT is below 92.5% of its nominal value. LBO works as a power-OK signal in this case. The LBI pin can be connected to a resistive-divider to monitor a particular definable voltage and compare it with a 0.6V internal reference. If LBI is connected to GND an internal resistive-divider is activated and connected to the output. Therefore, the Power-OK functionality can be realized with no additional external components. al id The Power-OK feature is not active during shutdown and provides a power-on-reset function that can operate down to VIN = 0.7V. A capacitor to GND may be added to generate a power-on-reset delay. To obtain a logic-level output, connect a pull-up resistor R3 from pin LBO to pin VOUT. Larger values for this resistor will help to minimize current consumption; a 100kΩ resistor is perfect for most applications (see Figure 16 on page 13). lv For the circuit shown in the left of Figure 15, the input bias current into LBI is very low, permitting large-value resistor-divider networks while maintaining accuracy. Place the resistor-divider network as close to the device as possible. Use a defined resistor for R2 and then calculate R1 as: V IN R 1 = R 2 ⋅ ----------- – 1 V LBI VLBI is 0.6V ±30mV am lc s on A te G nt st il Where: (EQ 18) Figure 15. Typical Application with Adjustable Battery Monitoring L1 6.8µH 3 VIN 0.7V to 3.6V LX 8 C1 22µF VIN R1 1 LBI R2 On Off Low Battery Detect 6 LBO R3 VOUT 1.8V to 3.3V 4 AS1310 VOUT C2 22µF 5 7 REF EN GND ca 2 CREF 100nF ni Figure 16. Typical Application with LBO working as Power-OK ch VIN 0.7V to 3.6V LX 3 8 1 LBI On Off LBO AS1310 R3 VOUT 1.8V to 3.3V 4 VOUT C2 22µF 5 7 REF EN 2 www.austriamicrosystems.com/DC-DC_Step-Up/AS1310 Low Battery Detect 6 VIN C1 22µF Te L1 6.8µH CREF 100nF GND Revision 1.8 13 - 19 AS1310 Datasheet - A p p l i c a t i o n I n f o r m a t i o n 9.1.2 Thermal Shutdown To prevent the AS1310 from short-term misuse and overload conditions the chip includes a thermal overload protection. To block the normal operation mode all switches will be turned off. The device is in thermal shutdown when the junction temperature exceeds 150°C. To resume the normal operation the temperature has to drop below 140°C. Note: Continuing operation in thermal overload conditions may damage the device and is considered bad practice. 9.2 Always On Operation al id A good thermal path has to be provided to dissipate the heat generated within the package. Otherwise it’s not possible to operate the AS1310 at its usable maximal power. To dissipate as much heat as possible from the package into a copper plane with as much area as possible, it’s recommended to use multiple vias in the printed circuit board. It’s also recommended to solder the Exposed Pad (pin 9) to the GND plane. lv In battery powered applications with long standby times as blood glucose meters, remote controls, soap dispensers, etc., a careful battery management is required. Normally a complex power management control makes sure that the DCDC is only switched on, when it is really needed. With AS1310 this complex control can be saved completely, since the AS1310 is perfectly suited to support always-on operations of the application. The efficiency at standby currents of e.g. 2µAs is around 45% (see Figure 17). 100 90 L1: XPL2010-682M 80 Efficiency (%) am lc s on A te G nt st il Figure 17. Efficiency vs. Output Current for Always ON Operation 70 60 50 40 30 20 Vin = 1.1V 10 0 0.001 Vin = 1.5V 0.01 0.1 1 10 100 Output Current (mA) ca 9.3 Component Selection Only four components are required to complete the design of the step-up converter. The low peak currents of the AS1310 allow the use of low value, low profile inductors and tiny external ceramic capacitors. ni 9.4 Inductor Selection ch For best efficiency, choose an inductor with high frequency core material, such as ferrite, to reduce core losses. The inductor should have low DCR (DC resistance) to reduce the I²R losses, and must be able to handle the peak inductor current without saturating. A 6.8µH inductor with a >500mA current rating and <500mΩ DCR is recommended. Table 4. Recommended Inductors L DCR Current Rating Dimensions (L/W/T) XPL2010-682M 6.8µH 421mΩ 0.62A 2.0x1.9x1.0 mm EPL2014-682M 6.8µH 287mΩ 0.59A 2.0x2.0x1.4 mm LPS3015-682M 6.8µH 300mΩ 0.86A 3.0x3.0x1.5 mm LPS3314-682M 6.8µH 240mΩ 0.9A 3.3x3.3x1.3 mm LPS4018-682M 6.8µH 150mΩ 1.3A 3.9x3.9x1.7 mm XPL7030-682M 6.8µH 59mΩ 9.4A 7.0x7.0x3.0 mm Te Part Number www.austriamicrosystems.com/DC-DC_Step-Up/AS1310 Revision 1.8 Manufacturer Coilcraft www.coilcraft.com 14 - 19 AS1310 Datasheet - A p p l i c a t i o n I n f o r m a t i o n Table 4. Recommended Inductors Part Number L DCR Current Rating Dimensions (L/W/T) LQH32CN6R8M53L 6.8µH 250mΩ 0.54A 3.2x2.5x1.55 mm LQH3NPN6R8NJ0L 6.8µH 210mΩ 0.7A 3.0x3.0x1.1 mm LQH44PN6R8MJ0L 6.8µH 143mΩ 0.72A 4.0x4.0x1.1 mm Manufacturer Murata www.murata.com al id 9.5 Capacitor Selection Table 5. Recommended Input and Output Capacitors C TC Code Rated Voltage Dimensions (L/W/T) 22µF X5R 6.3V 0805, T=1.25mm GRM31CR61C226KE15 22µF X5R 16V 1206, T=1.6mm 47µF X5R 6.3V 1206, T=1.6mm GRM31CR60J475KA01 Manufacturer Murata www.murata.com am lc s on A te G nt st il Part Number GRM21BR60J226ME99 lv The convertor requires three capacitors. Ceramic X5R or X7R types will minimize ESL and ESR while maintaining capacitance at rated voltage over temperature. The VIN capacitor should be 22µF. The VOUT capacitor should be between 22µF and 47µF. A larger output capacitor should be used if lower peak to peak output voltage ripple is desired. A larger output capacitor will also improve load regulation on VOUT. See Table 5 for a list of capacitors for input and output capacitor selection. On the pin REF a 10nF capacitor with an Insulation resistance >1GΩ is recommended. Table 6. Recommended Capacitors for REF Part Number GRM188R71C104KA01 GRM31CR61C226KE15 C TC Code Insulation Resistance Rated Voltage Dimensions (L/W/T) Manufacturer 100nF X7R >5GΩ 16V 0603, T=0.8mm 100nF X7R >5GΩ 50V 0805, T=1.25mm Murata www.murata.com 9.6 Layout Considerations Te ch ni ca Relatively high peak currents of 480mA (max) circulate during normal operation of the AS1310. Long printed circuit tracks can generate additional ripple and noise that mask correct operation and prove difficult to “de-bug” during production testing. Referring to Figure 1, the input loop formed by C1, VIN and GND pins should be minimized. Similarly, the output loop formed by C2, VOUT and GND should also be minimized. Ideally both loops should connect to GND in a “star” fashion. Finally, it is important to return CREF to the GND pin directly. www.austriamicrosystems.com/DC-DC_Step-Up/AS1310 Revision 1.8 15 - 19 AS1310 Datasheet 10 Package Drawings and Markings The device is available in a TDFN (2x2) 8-pin package. al id Figure 18. Drawings and Dimensions am lc s on A te G nt st il lv XXX A2 Min 0.51 0.00 0.225 0.18 1.45 0.75 - Nom 0.55 0.02 0.15 REF 0.325 0.25 2.00 BSC 2.00 BSC 0.50 BSC 1.60 0.90 0.15 0.10 0.10 0.05 0.08 0.10 8 Max 0.60 0.05 0.425 0.30 1.70 1.00 - Te ch ni ca Symbol A A1 A3 L b D E e D2 E2 aaa bbb ccc ddd eee fff N Notes: 1. 2. 3. 4. 5. Dimensioning & tolerancing conform to ASME Y14.5M-1994. All dimensions are in millimeters. Angles are in degrees. Coplanarity applies to the exposed heat slug as well as the terminal. Radius on terminal is optional. N is the total number of terminals. www.austriamicrosystems.com/DC-DC_Step-Up/AS1310 Revision 1.8 16 - 19 AS1310 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 Revision History Revision Date Owner Description Initial revision 1.6 06 Mar, 2012 1.7 27 Apr, 2012 1.8 17 Aug, 2012 afe Updated Detailed Description and Application Information sections Detailed Description section updated Updated thermal resistance value and (EQ 17) Te ch ni ca am lc s on A te G nt st il lv Note: Typos may not be explicitly mentioned under revision history. al id 1.0 www.austriamicrosystems.com/DC-DC_Step-Up/AS1310 Revision 1.8 17 - 19 AS1310 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 7. Table 7. Ordering Information Marking Output Delivery Form Package A2 1.8V Tape and Reel TDFN (2x2) 8-pin AS1310-BTDT-20 A8 2.0V Tape and Reel TDFN (2x2) 8-pin AS1310-BTDT-25 A9 2.5V Tape and Reel TDFN (2x2) 8-pin AS1310-BTDT-27 A7 2.7V Tape and Reel TDFN (2x2) 8-pin AS1310-BTDT-30 A6 3.0V Tape and Reel TDFN (2x2) 8-pin 1 tbd 3.3V Tape and Reel TDFN (2x2) 8-pin 2 tbd tbd Tape and Reel TDFN (2x2) 8-pin AS1310-BTDT-xx Ultra Low Quiescent Current, Hysteretic DC-DC Step-Up Converter am lc s on A te G nt st il 1. On request 2. Non-standard devices are available between 1.8V and 3.3V in 50mV steps. lv AS1310-BTDT-33 Description al id Ordering Code AS1310-BTDT-18 Note: All products are RoHS compliant and austriamicrosystems green. Buy our products or get free samples online at ICdirect: http://www.austriamicrosystems.com/ICdirect Technical Support is available at http://www.austriamicrosystems.com/Technical-Support Te ch ni ca For further information and requests, please contact us mailto:[email protected] or find your local distributor at http://www.austriamicrosystems.com/distributor www.austriamicrosystems.com/DC-DC_Step-Up/AS1310 Revision 1.8 18 - 19 AS1310 Datasheet - O r d e r i n g I n f o r m a t i o n Copyrights Copyright © 1997-2012, 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. al id Disclaimer lv 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. ca Contact Information am lc s on A te G nt st il 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. Headquarters ni austriamicrosystems AG Tobelbaderstrasse 30 A-8141 Unterpremstaetten, Austria ch Tel: +43 (0) 3136 500 0 Fax: +43 (0) 3136 525 01 For Sales Offices, Distributors and Representatives, please visit: Te http://www.austriamicrosystems.com/contact www.austriamicrosystems.com/DC-DC_Step-Up/AS1310 Revision 1.8 19 - 19