SP6641BEK-5.0/TR

SP6641A EXAR | Alldatasheet

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Rev. 5/26/05, *Patent Pending SP6641A/6641B 500mA Alkaline DC/DC Boost Regulator in SOT-23 © Copyright 2002 Sipex Corporation

DESCRIPTION

The SP6641 is an ultra-low quiescent current, high efficiency, DC-DC boost converter designed for single and dual cell alkaline, or Li-ion battery applications found in PDA’s, MP3 players, and other handheld portable devices. The SP6641 features a 10µA quiescent current, a 0.3Ω N- channel charging switch, 0.9V input startup, and a 0.33A or 1.0A inductor current limiting feature. The SP6641 is offered in a 5 pin SOT-23 package and provides an extremely small power supply footprint optimized for portable applications. The SP6641 is preset to 3.3V and can be controlled by a 1nA active LOW shutdown pin. 500mA Alkaline DC/DC Boost Regulator in SOT-23 ■ Ultra Low Quiescent Current: 10µA ■ Wide Input Voltage Range: 0.9V to 4.5V ■ 90mA IOUT at 1.3V Input (SP6641A-3.3V) ■ 500mA IOUT at 2.6V Input (SP6641B-3.3V) ■ 100mA IOUT at 2.0V Input (SP6641A-5.0V) ■ 500mA IOUT at 3.3V Input (SP6641B-5.0V) ■ Fixed 3.3V or 5.0V Output Voltage ■ Up to 87% Efficiency ■ 0.3Ω NFET RDSon ■ Startup Voltage Guaranteed at 0.9V ■ 0.33A Inductor Current Limit (SP6641A) ■ 1A Inductor Current Limit (SP6641B) ■ Logic Shutdown Control ■ SOT-23-5 Package VOUT GND SHDN VBATTLX SP6641

5 Pin SOT-23

APPLICATIONS

■ PDA's ■ DSC's ■ CD/MP3 Players ■ Pagers ■ Digital Cameras ■ Portable Handheld Medical Devices SP6641A/6641B Figure 1. Typical Application Schematic Figure 2. Maximum Load Current in OperationIOUT (mA)

Rev. 5/26/05, *Patent Pending SP6641A/6641B 500mA Alkaline DC/DC Boost Regulator in SOT-23 © Copyright 2002 Sipex Corporation ABSOLUTE MAXIMUM RATINGS These are stress ratings only and functional operation of the device at these ratings or any other above those indicated in the operation sections of the specifications below is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability. ELECTRICAL SPECIFICATIONS VBATT = VSHDN = 1.3V, ILOAD = 0mA, -40°C <TA < +85°C, VOUT = +3.3V or +5.0V preset, typical values at 27°C unless otherwise noted. Reverse V PARAMETER MIN TYP MAX UNITS CONDITIONS Input Voltage Operating Range, 0.5 4.5 V after startup VBATT Startup Voltage, VBATT 0.85 0.90 V R LOAD=3kΩ, TA =27°C

1.00 V R LOAD=3kΩ,-40°C <TA < +85°C

Output Voltage, VOUT 3.16 3.30 3.44 V 3.3V V OUT preset 4.80 5.00 5.20 V 5.0V V OUT preset Quiescent Current into VOUT,1 0 1 5 µAV OUT=3.5V, 3.3V VOUT preset IQ(OUT) VOUT=5.5V, 5.0V VOUT preset Quiescent Current into VBATT, 250 500 nA V OUT=3.5V, 3.3V VOUT preset IQB VOUT=5.5V, 5.0V VOUT preset Shutdown Current into VOUT,1 500 nA V SHDN =0V ISHDN Shutdown Current into VBATT,2 0 100 nA V SHDN =0V ISHDN Inductor Current Limit 280 330 380 mA (SP6641A) Inductor Current Limit 850 1000 1150 mA (SP6641B) Output Current (SP6641AEK-3.3) 90 mA V BATT =1.3V 190 mA V BATT =2.6V Output Current (SP6641BEK-3.3) 200 mA V BATT =1.3V 500 mA V BATT =2.6V Output Current (SP6641AEK-5.0) 100 mA V BATT =2.0V 175 mA V BATT =3.3V Output Current (SP6641BEK-5.0) 275 mA V BATT =2.0V 500 mA V BATT =3.3V Minimum Off-Time Constant 1.50 V* µsT OFF ≥ KOFF / (VOUT – VIN) KOFF NMOS Switch Resistance 0.3 0.75 Ω Inmos=100mA SHDN Input Voltage Vil 20 % % of V BATT Vih 80 % % of V BATT SHDN Input Current 1 100 nA

Rev. 5/26/05, *Patent Pending SP6641A/6641B 500mA Alkaline DC/DC Boost Regulator in SOT-23 © Copyright 2002 Sipex Corporation PIN DESCRIPTION PIN NO. PIN NAME DESCRIPTION 1L X Inductor switching node. Connect one terminal of the inductor to the positive terminal of the battery. Connect the second terminal of the inductor to this pin. The inductor charging current flows into LX, through the internal charging N-channel FET, and out through the GND pin. 2 GND Ground pin. The internal regulator bias currents and the inductor charging current flows out of this pin. 3V OUT Output voltage sense pin, internal regulator voltage supply, and minimum off-time one shot input. Kelvin connect this pin to the positive terminal of the output capacitor, but for SP6641B, use 10Ω series resistor and 1µF bypass per Figure 1 schematic. 4 SHDN Shutdown. Tie this pin to V BATT for normal operation. Tie this pin the ground to disable all circuitry inside the chip. In shutdown mode, the output voltage will float at a diode drop below the battery potential. 5V BATT Battery voltage pin. The startup circuitry runs off of this pin. The regulating circuitry also uses this voltage to control the minimum off- time. T OFF ≥ KOFF / (VOUT – VIN). BLOCK DIAGRAM Internal VBATT VBATT Internal Supply SHDN V OUT Ref Block REFREADY REF GND Internal Ground IPK/M VOUT(LOW) LX C SU OSCEN Min. TOFF CFB SHDN VBATT VOUT VOUT SHDN VOUTNGATE DRIVER CHARGE R Q S Qn TOFF SUGATE VBATT VOUT LX M 1 ICHN SP6641 LOAD VBATT VOUT ITH

Rev. 5/26/05, *Patent Pending SP6641A/6641B 500mA Alkaline DC/DC Boost Regulator in SOT-23 © Copyright 2002 Sipex Corporation IOUT(MAX) ≈ η ( V IN ) ( IPK – KOFF )V OUT 2L OPERATION General Overview The SP6641 is a high efficiency, low quiescent current step-up DC-DC converter ideal for single and dual cell alkaline and single cell Lithium Ion battery applications such as medical monitors, PDA’s, MP3 players, and other portable end products. The SP6641’s 10µA quiescent cur- rent, low 0.3Ω NFET switch, and unique PFM control scheme combine to provide excellent efficiency over a wide output power range. Other features include a logic level enable con- trol pin, guaranteed 0.9V startup, a tiny SOT23 5 pin package, and precise inductor peak current control. SP6641A sources up to 90mA at 1.3V, typ. and SP6641B sources up to 500mA at 2.6V, typ. by supporting different peak inductor current levels. Only two capacitors, an inductor, and a diode are required to build a power supply for the SP6641A. The SP6641B, 1A peak current requires an additional small resistor and capaci- tor as a low pass filter for the V OUT IC power pin. Loop Regulation The SP6641 combines a fixed inductor peak current limit, a feed-forward minimum off-time one-shot, and a precision loop comparator to regulate the output voltage. Under light-load conditions the loop operates as a standard PFM converter. The frequency of fixed amplitude inductor current triangles is modulated to regu- late the load. Under heavy load conditions, the converter adjusts the number of successive con- tinuous mode current pulses to regulate the load. Refer to the block diagram for the following explanation of operating modes in loop regulation. The output voltage is internally divided down and fed to the negative terminal of the loop compara- tor. A +1.25V bandgap reference voltage is ap- plied to the positive terminal of the comparator. As the output voltage droops below the regulation threshold due to the load the loop comparator output (signal V OUT(LOW) ) transitions to a logic “1”. This sets the SR latch and initiates inductor charging by pulling the signal NGATE high. In- ductor charging continues until the current reaches the internally programmed limit, at which point, the off-time one-shot is triggered. The off-time one-shot via signal T OFF resets the SR latch regardless of the SET state (VOUT(LOW) ), opens the NMOS charge switch, and forces the inductor to discharge through the rectifying diode for a minimum time defined by the one- shot duration. The end of the off-time pulse releases the SR latch, and its output state is once again determined by the output of the loop comparator (V OUT(LOW) ). Under light load con- ditions, the output voltage will have been pulled above the regulation threshold during the mini- mum off-time, the signal VOUT(LOW) will be a logic “0”, and the NMOS charging switch will remain open. The inductor current discharges until it reaches zero or the loop comparator triggers a new charge cycle. Under a heavy load, the output voltage will remain below the regulation point at the end of the off-time pulse. In this condition, V OUT(LOW) has a logic value of 1 which immediately starts a new charge/discharge cycle defined by the peak inductor current and the minimum off- time. The inductor current will remain in a continuous conduction mode until the loop com- parator indicates the output voltage is above the regulation threshold, and the inductor current will relax towards zero. During continuous mode bursts, the inductor current frequency and ripple amplitude are con- trolled by the minimum off-time one-shot and the input and output voltage levels. The SP6641 sets the minimum off-time to: TOFF = KOFF (VOUT – VIN), where: K OFF = Off-time Constant, typically 1.5µs*V V OUT = Output Voltage V IN = Input Voltage Plugging the TOFF expression into the boost mode equations yields the maximum output current in regulation: where: η = Efficiency, typically 0.80 to 0.90 IPK = Programmed inductor peak current, typi- cally 0.33A for the SP6641A, typically 1.0A for the SP6641B. L= Inductor value

Rev. 5/26/05, *Patent Pending SP6641A/6641B 500mA Alkaline DC/DC Boost Regulator in SOT-23 © Copyright 2002 Sipex Corporation The SP6641 feed forward off-time control de- livers more load current than constant off-time control because the input battery voltage drops during its life cycle. The term (I PK – KOFF /2L) is the average current delivered to the output ca- pacitor during the discharge phase. This is con- stant with respect to input and output voltage. With constant off-time control, the average dis- charge current term becomes PK -TOFF *(VOUT -VIN)/2L), which decreases as the input voltage drops. Table 1 illustrates the average inductor current delivered to the load during discharge versus the input voltage. The SP6641 feed forward off- time control and the constant off-time control are compared. For purposes of illustration, the off times of each control scheme are normalized at a typical two cell alkaline input voltage of 2.6V. The values used in Table 1 are: I PK = 0.33A L = 22µH V OUT = 3.3V TOFF (SP6641) = 1.5V*µs/(3.3-VIN) TOFF (constant) = 2.14µs SP6641A Constant T OFF V IN TOFF Avg IL TOFF Avg IL Table 1- Average IL vs. Input Voltage The following equation defines the burst mode frequency under heavy load conditions: where: V D = Forward schottky drop, (0.4V, typ) V C = Average charging switch drop, Rnmos*I PK , typically 0.1V Ignoring the conduction losses of VD and VC , the burst frequency equation simplifies to: FBURST = (VOUT – VIN)VIN K OFF V OUT Startup The internal regulator circuitry is bootstrapped to the VOUT pin. This requires a low voltage oscillator and charging switch powered from the V BATT pin to pump up the output voltage until the reference is established. The reference pro- vides a REFREADY signal that determines when output control is handed over to the regulator. REFREADY shuts down the startup circuit and enables the regulator when the reference is valid and V OUT is above +1.9V. Once the regulator is given control it will continue to pump up the output at full power until regulation is reached. For two cell alkaline input voltages and above, the output voltage will be pulled above +1.9V quickly through the rectifying diode before the reference has a chance to establish. In this sce- nario the startup circuit will coarsely regulate around +2.8V until the REFREADY signal as- serts. This keeps the output from overshooting in startup with higher input voltages. Startup is guaranteed at +0.9V at room tempera- ture with a 3kΩ load. Heavier loads will require a higher input voltage. Shutdown/Enable Control Pin 4 of the device is a V BATT referred control pin that shuts down the converter with the pin tied to ground, or enables the converter with the pin tied to V BATT . When the converter is shut- down the power switch is opened and all circuit biasing is extinguished leaving only junction leak- age currents on supply pins 3 and 5. The output voltage will droop to one diode drop below the battery voltage through the rectifying diode. After pin 4 is brought high, the startup circuit is enabled and starts pumping up the output until REFREADY hands over control to the internal regulator. OPERATION Loop Regulation: continued FBURST = ( V OUT – VIN ) ( VIN – VC )K OFF VOUT + VD –VC

Rev. 5/26/05, *Patent Pending SP6641A/6641B 500mA Alkaline DC/DC Boost Regulator in SOT-23 © Copyright 2002 Sipex Corporation

APPLICATION INFORMATION

Printed circuit board layout is a critical part of a power supply design. Poor designs can result in excessive EMI on the voltage gradients and feedback paths on the ground planes with appli- cations involving high switching frequencies and large peak currents. Excessive EMI can result in instability or regulation errors. All power components should be placed on the PC board as closely as possible with the traces kept short, direct, and wide (>50mils or 1.25mm). Extra copper on the PC board should be inte- grated into ground as a pseudo-ground plane. On a multilayer PC board, route the star ground using component-side copper fill, then connect it to the internal ground plane using vias. For the SP6641A/6641B devices, input and output fil- ter capacitors should be soldered with their ground pins as close together as possible in a star-ground configuration. The VOUT pin must be bypassed directly to ground as close to the SP6641A/6641B devices as possible (within 0.2in or 5mm). The DC-DC converter and any digital circuitry should be placed on the oppo- site corner of the PC board as far away from sensitive RF and analog input stages. Noisy traces, such as from the LX pin, should be kept away from the voltage-feedback VOUT node and separated from it using grounded copper to minimize EMI. See the SP6641A/6641B Evalu- ation Board Manual for PC Board Layout de- sign details. Component Selection Selection of capacitors, inductors and schottky diodes for SP6641A and SP6641B power sup- ply circuits can be made through the use of Table 1 component selection. Capacitor equiva- lent series resistance is a major contributor to output ripple, usually greater than 60%. Low ESR capacitors are recommended. Ceramic ca- pacitors have the lowest ESR. Low-ESR tanta- lum capacitors may be a more acceptable solu- tion having both a low ESR and lower cost than large ceramic capacitors. Designers should se- lect input and output capacitors with a rating exceeding the peak inductor current. Do not allow tantalum capacitors to exceed their ripple- current ratings. For example, in the SP6641A a 22µF, 6V, low-ESR, surface-mount tantalum output filter capacitor typically provides 60mV output ripple when stepping up from 1.3V to 3.3V at 20mA. An input filter capacitor can reduce peak currents drawn from the battery and improve efficiency. Low-ESR aluminum elec- trolytic capacitors are acceptable in some appli- cations but standard aluminum electrolytic ca- pacitors are not recommended. In selecting an inductor, the saturation current specified for the inductor needs to be greater then the SP6641A/B peak current to avoid satu- rating the inductor, which would result in a loss in efficiency and could damage the inductor. The SP6641A evaluation board uses a Sumida CDRH5D28 22 µH inductor with an Isat value of 0.9A and a DCR of 0.095Ω, which easily handles the Ipeak of 0.33A of the SP6641A and will deliver high efficiencies. The SP6641B evaluation board uses a Sumida CDRH5D28 10µH inductor with an Isat value of 1.3A and a DCR of 0.065Ω, which easily handles the Ipeak of 1.0A of the SP6641B and will deliver high efficiencies. Other inductors could be selected provided their Isat is greater than the Ipeak of the SP6641A/SP6641B. Output Filter or LDO Regulator Designers could add LC pi filters, linear post- regulators, or shielding in applications necessary to address excessive noise, voltage ripple, or EMI concerns. The LC pi filter’s cutoff frequency should be at least a decade or two below the DC-DC converters’ switching frequency for the specified load and input voltage. The SP6201, a small SOT23- 5pin 200mA Low Drop Out linear regulator can be used at the SP6641A/6641B output to reduce output noise and ripple. The schematic in figure 15 illustrates this circuit on the SP6641A Evaluation Board with the SP6641 3.3V output followed by the Sipex SP6201 3.0V output Low Drop Out linear regulator.

TABLE 1. COMPONENT SELECTION Note: Components highlighted in bold are those used on the SP6641A or SP6641B Evaluation Board. is low until the processor voltage comes up.

TABLE 2. SP6641A Resistive Load Current in Startup - low cost inductors Figure 15. SP6641A 3.3V Evaluation Board with SP6201 LDO Regulator Memory while a battery is changed.

Rev. 5/26/05, *Patent Pending SP6641A/6641B 500mA Alkaline DC/DC Boost Regulator in SOT-23 © Copyright 2002 Sipex Corporation PACKAGE: 5 Lead SOT23 SYMBOL A b C D E L e a 1.45 0.15 1.30 0.50 0.20 3.10 3.00 1.75 0.55 O 0.90 0.00 0.90 0.25 0.09 2.80 2.60 1.50 0.35 O MIN MAX 0.95ref 1.90ref E A e CLb D CL A A .10 CL E1 L 2 0.20 DATUM 'A' C a

Rev. 5/26/05, *Patent Pending SP6641A/6641B 500mA Alkaline DC/DC Boost Regulator in SOT-23 © Copyright 2002 Sipex Corporation

ORDERING INFORMATION

Part Number TOP MARK Temperature Range Package Type Corporation SIGNAL PROCESSING EXCELLENCE Sipex Corporation reserves the right to make changes to any products described herein. Sipex does not assume any liability aris ing out of the application or use of any product or circuit described herein; neither does it convey any license under its patent rights nor t he rights of others. Sipex Corporation Headquarters and Sales Office

22 Linnell Circle

Billerica, MA 01821 TEL: (978) 667-8700 FAX: (978) 670-9001 e-mail: sales@sipex.com Sales Office

233 South Hillview Drive

Milpitas, CA 95035 TEL: (408) 934-7500 FAX: (408) 935-7600 Available in lead free packaging. To order add “-L” suffix to part number. Example: SP6641AEK-3.3/TR = standard; SP6641AEK-L-3.3/TR = lead free, Top Mark “H4”. /TR = Tape and Reel Pack quantity is 2,500 for SOT23.