AS1326

AS1326 H i g h C u r r e n t , 0 . 8 A D C - D C St e p - U p C o n v e r t e r s D a ta S he e t 1 General Description The AS1326A/AS1326B are high-efficiency, high current, DC-DC step-up converters specifically designed for battery-powered wireless applications. Low quiescent supply current (65µA), high operating frequency (1MHz), and minimal external component requirements make these devices perfect for small hand-held applications. Table 1. Standard Products Model AS1326A AS1326B Input Signal Activation Logic-Low On Logic-High On 2 Key Features ! ! ! ! ! ! ! ! ! Up to 800mA Output Constant-Frequency (1MHz) Operation Up to 96% Efficiency Input Range: 0.7 to 5.0V Fixed Output: 3.3V Adjustable Output: 2.5 to 5.0V PWM Synchronous-Rectified Technology Logic-Controlled Shutdown: 0.1µA Synchronizable Switching Frequency (0.5 to 1.2MHz) Adjustable Current Limit Adjustable Soft-Start 10-pin TDFN (3.0mm x 3.0mm) Package Both devices use synchronous-rectified pulse-width modulation (PWM) boost technology to generate 2.5 to 5.0V outputs from a wide range of inputs, such as 1 to 3 alkaline/NiCd/NiMH cells or a single lithium-ion (Li+) cell. Automatic powersave operation significantly improves efficiency at light-loads. Continuous switching mode is available for applications requiring constant-frequency operation at all load currents. PWM operation can also be synchronized to an external clock to protect sensitive frequency bands in communications equipment. Analog soft-start and adjustable current limit permit optimization of rush in current and external component size. The AS1326A/AS1326B are available in a 10-pin TDFN (3.0mm x 3.0mm) package. ! ! ! 3 Applications The devices are ideal for digital cordless phones. mobile phones, wireless handsets, hand-held instruments, PDAs, two-way pagers, and any battery-operated equipment. Figure 1. Block Diagram 5 OUT IC Power 2.15V AS1326B only AS1326A only 10 ON 10 ONN 2 REF 3 GND 6 CLK/SEL 4 FB 1 ISET + – Undervoltage Lockout AS1326 9 On Q Startup Osc D Controller 8 En Osc Mode LX 7 PGND FB ISET POUT On Rdy 1.25V Reference Ref GND En Osc 1MHz Osc CLK/SEL Mode www.austriamicrosystems.com Revision 1.02 1 - 18 AS1326 Data Sheet - P i n o u t 4 Pinout Pin Assignments Figure 2. Pin Assignments (Top View) ISET 1 REF 2 GND 3 FB 4 OUT 5 11 10 ONN/ON 9 POUT AS1326A/ AS1326B 8 LX 7 PGND 6 CLK/SEL Pin Descriptions Table 2. Pin Descriptions Pin Number 1 2 3 4 Pin Name ISET REF GND FB Description N-Channel Current-Limit Control. For maximum current limit, connect to pin REF. To reduce current, supply a voltage between pin REF and GND using a resistive voltage-divider. If soft-start is desired, connect a capacitor from this pin to GND. 1.250V Internal Reference Bypass. Connect a 10nF ceramic bypass capacitor to GND. Up to 50µA of external load current is allowed. Ground. Connect this pin to PGND using a short trace. The exposed pad can be used for this routing. DC-DC Converter Feedback Input. To set fixed output voltage of +3.3V, connect this pin to GND. For adjustable output of 2.5 to 5.0V, connect to a resistor-divider network from pin OUT to GND. The set point for this pin is 1.24V. IC Power, Supplied from the Output. Bypass this pin to GND with a 330nF ceramic capacitor, and connect to POUT with a 10Ω series resistor (see Figure 19 on page 11). Clock Input for the DC-DC Converter. This pin is also used to program the operational mode as follows: 0 = Normal operation – the AS1326A operates at a fixed frequency, and switches into automatic powersave operation if the load is minimized. 1 = Forced-PWM mode – the AS1326A operates in low-noise, constant-frequency mode at all loads. Clocked = Forced-PWM mode with the internal oscillator synchronized to this pin in 500 to 1200kHz range. N-Channel Power MOSFET Switch Source Inductor Connection Power Output. P-channel synchronous rectifier source. Enable Low (AS1326A only). Must be connected to GND for normal operation. 0 = The AS1326A is on. 1 = The AS1326A is off. Enable High (AS1326B only). Must be connected to OUT for normal operation. 0 = The AS1326B is off. 1 = The AS1326B is on. Exposed Pad. This pad is not connected internally. It can be used for ground connection between GND and PGND. 5 OUT 6 CLK/SEL 7 8 9 PGND LX POUT ONN 10 ON 11 NC www.austriamicrosystems.com Revision 1.02 2 - 18 AS1326 Data Sheet - 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 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 ON, ONN, OUT, CLK/SEL to GND PGND to GND REF, FB, ISET, POUT to GND LX to PGND POUT to OUT Thermal Resistance ΘJA Operating Temperature Range Storage Temperature Range Junction Temperature -40 -65 Min -0.3 -0.3 -0.3 -0.3 -0.3 Max 7 +0.3 VOUT + 0.3 VPOUT + 0.3 +0.3 33 +85 +150 +150 Units V V V V V ºC/W ºC ºC ºC The reflow peak soldering temperature (body temperature) specified is in accordance with IPC/JEDEC J-STD-020C “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 1.02 3 - 18 AS1326 Data Sheet - 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 CLK/SEL = FB = PGND = GND, ISET = REF, OUT = POUT, VOUT = 3.6V, TAMB = -40 to +85ºC. Typical values are at TAMB = +25ºC. Unless otherwise specified. Table 4. Electrical Characteristics Symbol DC-DC Converter VIN VMINSU Input Voltage Range 1 2 Parameter Condition Min Typ Max Unit 0.7 ILOAD < 1mA, TAMB = +25ºC 0.9 -1.6 VOUT = 1.5V CLK/SEL = OUT 125 0.8 80 0.5 VFB < 0.1V, CLK/SEL = OUT, includes load regulation for 0 < ILX < 0.55A 3.17 3.3 1.240 0.01 -1 2.5 Rising edge VISET = 1.25V, TAMB = +25ºC VON = 0V, VONN = 3.6V CLK/SEL = GND CLK/SEL = OUT 2.00 -50 2.15 0.01 0.1 65 2 500 1 86 5.0 1.1 V V mV/°C Minimum Startup Voltage Temperature Coefficient of Startup Voltage fSU fSW Frequency in Startup Mode Internal Oscillator Frequency Oscillator Maximum 3 Duty Cycle fSWEXT VOUT VFB IFB External Clock Frequency Range Output Voltage FB Regulation Voltage FB Input Leakage Current Load Regulation VOUTADJ Output Voltage Adjust Range Output Voltage 4 Lockout Threshold ISET Input Leakage Current ISHDN Supply Current in Shutdown No-Load Supply Current 5 5 1000 1.2 90 1.2 3.38 1.270 100 kHz MHz % MHz V V nA % Adjustable output, CLK/SEL = OUT, includes load regulation for 0 < ILX < 0.55A 1.215 VFB = 1.35V, TAMB = +25ºC CLK/SEL = OUT, no load to full load, 0 < ILX < 1.0A -100 5.0 2.30 50 5 100 V V nA µA µA mA No-Load Supply Current , Forced PWM Mode DC-DC Switches POUT Leakage Current LX Leakage Current RON INMOS References VREF Reference Output Voltage Reference Load Regulation Reference Supply Rejection Switch On-Resistance N-Channel Current Limit VLX = 0, VOUT = 5.5V, TAMB = +25ºC VLX = VOUT = 5.5V, in shutdown, TAMB = +25ºC N-channel P-channel 1.25 0.1 0.1 0.2 0.25 1.6 10 10 0.35 0.45 1.95 µA µA Ω A IREF = 0 -1µA < IREF < +50µA 2.5V < VOUT < 5V 1.230 1.250 5 0.2 1.270 15 6 V mV mV www.austriamicrosystems.com Revision 1.02 4 - 18 AS1326 Data Sheet - 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 4. Electrical Characteristics (Continued) Symbol Logic Inputs CLK/SEL Input Low Level CLK/SEL Input High Level ON, ONN Input Low Level 6 Parameter Condition Min Typ Max Unit 2.5V ≤ VOUT ≤ 5.0V 2.5V ≤ VOUT ≤ 5.0V 1.1V ≤ VOUT ≤ 1.8V 1.8V ≤ VOUT ≤ 5.0V 6 0.2 x VOUT 0.8 x VOUT 0.2 0.4 VOUT 0.2 1.6 0.1 200 100 1 V V V 1.1V ≤ VOUT ≤ 1.8V 1.8V ≤ VOUT ≤ 5.0V CLK/SEL, ON, ONN, TAMB = +25ºC ON, ONN Input High Level Input Leakage Current Minimum CLK/SEL Pulse Width Maximum CLK/SEL Rise/Fall Time V µA ns ns 1. Operating voltage; since the regulator is bootstrapped to the output, once started, the AS1326 operates down to 0.7V input. If CLK/SEL = GND then VIN ≤ VOUT. If CLK/SEL = VOUT then VIN ≤ 0.75xVOUT. 2. Startup is tested with the circuit shown in Figure 25 on page 14. 3. Defines maximum step-up ratio. 4. The regulator is in startup mode until this voltage is reached. Caution: Do not apply full load current until the device output > 2.3V. 5. Supply current into pin OUT. This current correlates directly to the actual battery-supply current, but is reduced in value according to the step-up ratio and efficiency. 6. ON and ONN have a hysteresis of typically 0.15V. www.austriamicrosystems.com Revision 1.02 5 - 18 AS1326 Data Sheet - 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 Circuit of Figure 19, VIN = 2.4V, VOUT = 3.3V, TA = +25°C, unless otherwise noted. Figure 3. Efficiency vs. Output Current, VOUT = 3.3V 100 90 80 VIN = 1.2V Powersave Mode VIN = 2.4V Figure 4. Efficiency vs. Output Current, VOUT = 5.0V 100 Powersave Mode 90 VIN = 3.6V 80 VIN = 3.0V Efficiency (%) . 70 60 50 40 30 20 10 0 0.1 1 10 100 1000 Continuous Mode VIN = 0.9V Efficiency (%) . 70 60 VIN = 2.4V 50 40 30 20 10 0 0.1 1 10 100 1000 Continuous Mode Output Current (mA) Output Current (mA) Figure 5. Maximum Output Current vs. Input Voltage; 900 800 Figure 6. No-Load Current vs. Input Voltage; 500 . Output Current (mA) 700 VOUT = 3.3V 600 500 400 300 200 100 0.5 1 1.5 2 2.5 3 3.5 4 VOUT = 5V Input Current (µA) . 400 300 VOUT = 5V 200 VOUT = 3.3V 100 0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 Input Voltage (V) Input Voltage (V) Figure 7. Internal Oscillator Frequency vs. Temp; 1.2 1.15 Figure 8. Total Shutdown Current vs. Input Voltage 10 1.05 1 0.95 0.9 0.85 0.8 0.75 -40 Shutdown Current (µA) -15 10 35 60 85 Frequency (MHz) . 1.1 . 1 0.1 0.01 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 Temperature (°C) Input Voltage (V) www.austriamicrosystems.com Revision 1.02 6 - 18 AS1326 Data Sheet - 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. Startup Voltage vs. Output Current 2.5 Figure 10. Peak Inductor Current vs. VISET 1.6 . 2 1.4 1.2 1 0.8 0.6 0.4 0.2 0 1.5 +25°C 1 +85°C -40°C 0.5 1 10 100 1000 Peak Inductor Current (A) Startup Voltage (V) . 0 0.2 0.4 0.6 0.8 1 1.2 1.4 Output Current (mA) VISET (V) Figure 11. Light-Load Switching Waveform IOUT = 10mA, CLK/SEL = OUT Figure 12. Heavy-Load Switching Waveform IOUT = 500mA 5V/Div LX pin 200mA/Div LX pin Output Ripple 50mV/Div Output Ripple 500ns/Div 500ns/Div Figure 13. Line-Transient Response. VIN =2.4 to 1.4V, IOUT = 200mA Figure 14. Noise Spectrum CLK/SEL = OUT 4 3.5 3 2.5 2 1.5 1 0.5 0 0.2 1 10 20 1V/Div Vin 500ns/Div 50mV/Div VOUT Noise (mV RMS ) . Frequency (MHz) www.austriamicrosystems.com Revision 1.02 50mV/Div 200mA/Div Inductor Current Inductor Current 5V/Div 7 - 18 AS1326 Data Sheet - 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 Transient Response; Automatic Powersave Mode, CLK/SEL = GND Figure 16. Load Transient Response Continuous Switching, CLK/SEL = OUT 100mA/Div 0mA 0mA 50mV/Div 100ms/Div 100ms/Div Figure 17. Turn-On Waveform No Soft Start Figure 18. Turn-On Waveform Soft Start, RSS = 220kΩ ,CSS = 100nF 5V/Div 500mA/Div 2V/Div VOUT 2ms/Div VOUT 2ms/Div Parts used for measurments: 3.3µH (Coilcraft MOS6020-332ML) Inductor, 33µF (Panasonic EEFCD0K330R) CIN, 100µF (Panasonic EEFUD0J101R) COUT www.austriamicrosystems.com Revision 1.02 2V/Div 200mA/Div Inductor Current Inductor Current 5V/Div ONN ONN 50mV/Div VOUT VOUT 100mA/Div IOUT IOUT 8 - 18 AS1326 Data Sheet - D e t a i l e d D e s c r i p t i o n 8 Detailed Description The AS1326A/AS1326B are high-efficiency, low-noise DC-DC boost converters suitable as power supplies for portable devices. Both devices feature integrated boost switching regulator, N-channel power MOSFET, P-channel synchronous rectifier, precision reference, and shutdown control circuitry (see Figure 1 on page 1). The AS1326A/AS1326B are able to boost a 1- to 3-cell battery voltage input to a fixed 3.3V output, or adjustable output between 2.5 and 5.0V (an external Schottky diode is required for output voltages greater than 4V). Table 5. Typical Output Voltages and Currents # of NiCd/NiMh Cells 1 2 3 Input Voltage (V) 1.2 2.4 2.4 3.6 Output Voltage (V) 3.3 3.3 5.0 5.0 Output Current (mA) 335 800 450 800 The devices are guaranteed to startup with an input voltage as low as 1.1V and remain operational down to an input of as little as 0.7V, and are optimized for use in mobile phones and other RF applications which have low noise and low quiescent current (extended battery life) requirements. The integrated shutdown circuitry reduces device quiescent current down to 0.1µA. Step-Up Converter During boost operation, the internal N-channel MOSFET switch turns on for the first part of each cycle, allowing current to ramp up in the inductor and store energy in a magnetic field. During the second part of each cycle, the MOSFET turns off and inductor current flows through the synchronous rectifier to the output filter capacitor and the load. As the energy stored in the inductor is depleted, the current ramps down and the synchronous rectifier turns off. At light loads, the device operates at fixed-frequency or only as needed to maintain regulation, depending on the setting of pin CLK/SEL (see Table 6). Operational Modes The AS1326A/AS1326B are capable of operating in 3 different modes (see Table 6) as controlled by pin CLK/SEL (see page 2). Table 6. Operational Modes CLK/SEL Setting 0 1 External 500kHz to 1.2MHz clock Operational Mode Normal Forced PWM Synchronized PWM Description High-efficiency at all loads; Fixed-frequency (1MHz) at heavy and medium loads. Fixed-frequency (1MHz), low-noise at all loads. VIN ≤ 0.75xVOUT Fixed-frequency, low-noise at all loads. VIN ≤ 0.75xVOUT Normal Operation When CLK/SEL is pulled low, the devices are in normal operating mode. In normal mode the devices operate in PWM when driving medium-to-heavy loads, and automatically switches to automatic powersave mode if the load requires less power. The use of automatic powersave mode will boost the efficiency futhermore at light-load conditions. Forced-PWM Operation Pulling CLK/SEL high, selects the low-noise PWM-only mode. During forced-PWM operation, the devices switch at a constant frequency (1MHz) and modulates the MOSFET switch pulse width to control the power transferred per cycle to regulate the output voltage. Switching harmonics generated by fixed-frequency operation are consistent and can be filtered. See the Noise Spectrum plot in the Typical Operating Characteristics (see Figure 14 on page 7). www.austriamicrosystems.com Revision 1.02 9 - 18 AS1326 Data Sheet - D e t a i l e d D e s c r i p t i o n Synchronized-PWM Operation In PWM mode the AS1326A/AS1326B can be synchronized with an external clock (500kHz to 1.2MHz) by applying an external clock signal to pin CLK/SEL. This synchronization will minimize interference in wireless applications since the operating frequency can be set to a preferred value. The synchronous rectifier is active during synchronized-PWM operation. Synchronous Rectifier The AS1326A/AS1326B feature an integrated, P-channel synchronous rectifier for enhanced efficiency operation. Synchronous rectification provides 5% improved efficiency over similar non-synchronous boost regulators. In PWM mode, the synchronous rectifier is turned on during the second half of each switching cycle. In low-power mode, an internal comparator turns on the synchronous rectifier when the voltage at LX exceeds the boost regulator output. Note: While operating with output voltages greater than 4V, an external 0.5A Schottky diode must be connected in parallel with the P-channel synchronous rectifier. Low-Voltage Startup Oscillator The AS1326A/AS1326B contain a CMOS, low-voltage startup oscillator for a 1.1V guaranteed minimum startup input voltage. At startup, the low-voltage oscillator switches on the N-channel MOSFET until the output voltage reaches 2.15V. With output voltages > 2.15V, the boost-converter feedback and control circuitry are acitvated. When the AS1326A/AS1326B is in regulation, it can operate down to 0.7V input since internal power for the device is bootstrapped from the output through pin OUT. Caution: Do not apply full load until the output > 2.3V. Shutdown The AS1326A/AS1326B feature an integrated shutdown mode that reduces quiescent current to 0.1µA. During shutdown mode (ONN = 1 on AS1326A, ON = 0 on AS1326B), the internal reference and feedback/control circuitry are disabled. Note: During shutdown, the output voltage is one diode drop below the input voltage. Reference The AS1326A/AS1326B contain an internal reference (1.250V ±1%). A 10nF ceramic bypass capacitor must be connected between pins REF and GND. REF can source up to 50µA of external load current. Note: The bypass capacitor must be placed within 5mm (0.2”) of pin REF. www.austriamicrosystems.com Revision 1.02 10 - 18 AS1326 Data Sheet - 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 Figure 19. Typical AS1326A Application Circuit 3.3µH VIN = 2.4V 33µF + 8 LX 10 ONN 6 CLK/SEL 1 ISET 2 10nF REF 4 FB 3 GND 7 PGND 9 POUT VOUT = 3.3V 800mA AS1326A 5 OUT 10Ω 100µF + 330nF Setting the Output Voltages For a fixed 3.3V output, connect pin FB to GND. To set adjustable output voltages between 2.5 and 5.0V, connect a resistor voltage-divider to pin FB from pin OUT to GND (Figure 20). Figure 20. Application Circuit using External Feedback Resistors 3.3µH VIN = 2.4V 33µF + 8 LX 10 ONN 6 CLK/SEL 1 ISET 2 REF 10nF 3 GND 7 PGND 4 FB R2 9 POUT 10Ω 100µF + VOUT AS1326A 5 OUT R1 330nF For the circuit shown in Figure 20, the input bias current into FB is