SP6648ER-L

SP6648 Ultra-low Quiescent Current, High Efficiency Boost Regulator FEATURES ■ Ultra-low 12μA Quiescent Current ■ 400mA Output Current at 2.6V Input: 3.3VOUT ■ 94% Efficiency from 2 Cell to 3.3VOUT ■ Wide Input Operating Voltage: 0.85V to 4.5V ■ 3.3V Fixed or Adjustable Output ■ Integrated Synchronous Rectifier: 0.3Ω ■ 0.3Ω Switch ■ Anti-Ringing Switch Technology ■ Programmable Inductor Peak Current ■ Logic Shutdown Control ■ Under Voltage Lock-Out at 0.61V ■ Programmable Low-Battery Detect ■ Single or Dual Cell Alkaline ■ Small 10 pin DFN Package and Industry Standard 10 pin MSOP VBATT 1 10 V OUT 9 LX LBI 2 SP6648 LBON 3 10 Pin DFN RLIM 4 8 P GND 7 GND SHDN 5 6 FB Now Available in Lead Free Packaging APPLICATIONS ■ Camera Flash LED Driver ■ Wireless Mouse ■ PDA's ■ Pagers ■ Medical Monitors ■ Handheld Portable Devices ■ MP3 Players DESCRIPTION The SP6648 is an ultra-low quiescent current, high efficiency step-up DC-DC converter ideal for single cell, dual cell alkaline and Li-Ion battery applications such as digital still cameras, PDAs, MP3 players, and other portable devices. The SP6648 combines the high-load efficiency associated with PWM control, with the low quiescent current and excellent light-load efficiency of PFM control. The SP6648 features 12μA quiescent current, synchronous rectification, a 0.3Ω charging switch, anti-ringing inductor switch, programmable low-battery detect, under-voltage lockout and programmable inductor peak current. The device can be controlled by a 1nA active LOW shutdown pin. TYPICAL APPLICATION CIRCUIT 500 10μH VBATT 450 400 + 350 1 LBI LBON 2 3 4 SHDN 1.87K SP6648 VBATT LBI LBON RLIM 5 SHDN VOUT 10 3.3VOUT + LX 9 PGND 8 47μF Io (mA) 47μF 300 250 200 1μF 205K GND 7 47pF 150 100 FB 6 Vout=3.3V, Ipk=0.85A 50 Vout=5.0V, Ipk=0.85A 0 124K 1.0 1.5 2.0 2.5 3.0 Vin (V) 3.5 4.0 4.5 Maximum Load Current in Operation Date: 6/7/06 Rev B SP6648 Ultra-low Quiescent Current, High Efficiency Boost Regulator 1 © 2006 Sipex Corporation ABSOLUTE MAXIMUM RATINGS Operating Temperature ................................................ -40°C to +85°C ESD Rating ........................................................................ 1.5kV HBM LX, Vo, VBATT , LBON, FB to GND pin ................................ -0.3 to 6.0V SHDN, LBI ........................................................... -0.3V to VBATT +1.0V Vo, GND, LX Current ....................................................................... 2A Reverse VBATT Current .............................................................. 220mA Forward VBATT Current .............................................................. 500mA Storage Temperature .................................................. -65 °C to 150°C 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 = 2.6V, VFB=0.0V, ILOAD = 0mA, TAMB = -40°C to +85°C, VOUT = +3.3V, typical values at 27°C unless otherwise noted. The ♦ denotes the specifications which apply over full operating temperature range -40°C to +85°C, unless otherwise specified. PARAMETER MIN Input Voltage Operating Range, VBATT 0.7 Output Voltage Range, VOUT 2.5 Start-up Input Voltage, VBATT TYP MAX UNITS ♦ CONDITIONS 4.5 V ♦ After Startup ♦ 5.5 V 0.85 1.1 V ♦ V ♦ Under Voltage Lock-out/UVLO 0.5 0.61 0.7 Output Voltage, VO 3.12 RLOAD = 3kΩ 3.30 3.48 V ♦ Quiescent Current into VO, IQO 12 25 μA ♦ VOUT = 3.3V, VFB = 1.5V, Toggle SHDN Quiescent Current into VBATT, IQB 250 750 nA ♦ VOUT = 3.3V, VFB = 1.5V VSHDN = 0.0V Shutdown Current into VO, ISDO 1 500 nA ♦ Shutdown Current into VBATT, ISDB 250 750 nA ♦ Efficiency 84 92 Inductor Current Limit, IPK = 1600/RLIM 650 1300 Output Current 800 1600 % % 1000 2000 mA mA Internal Feedback Divider VSHDN = 0.0V, VBATT = 2.6V VBATT = 1.3V, IOUT = 100mA, RLIM =2kΩ VBATT = 2.6V, IOUT = 200mA, RLIM =2kΩ ♦ ♦ RLIM = 2kΩ RLIM = 1kΩ 100 200 mA mA VBATT = 1.3V, RLIM = 4kΩ VBATT = 2.6V, RLIM = 4kΩ 150 400 mA mA VBATT = 1.3V, RLIM =2kΩ VBATT = 2.6V, RLIM =2kΩ Minimum Off-Time Constant KOFF 0.5 1.0 1.5 V*μs ♦ KOFF ≤ TOFF (VOUT- VBATT) Maximum On-Time Constant KON 2.5 4.0 5.5 V*μs ♦ KON ≥ TON (VBATT) Enable Valid to Output Stable 300 500 μs NMOS Switch Resistance 0.30 0.6 Ω ♦ INMOS = 100mA PMOS Switch Resistance 0.30 0.6 Ω ♦ IPMOS = 100mA 1.25 1.31 V ♦ External feedback 1 100 nA ♦ VFB =1.3V 0.61 0.66 V ♦ FB Set Voltage, VFB 1.19 FB Input Current LBI Falling Trip Voltage 0.56 LBI Hysteresis 25 Low Output Voltage for LBON, VOL Leakage current for LBON SHDN Input Voltage, Note 1 VIL VIH VIL VIH SHDN Input Current LX Pin Leakage mV 0.4 V ♦ VBATT = 1.3V, ISINK = 1mA 1 μA ♦ VBATT = 1.3V, VLBON = 3.3V ♦ ♦ ♦ ♦ VBATT = 1.3V VBATT = 1.3V VBATT = 2.6V VBATT = 2.6V 0.25 1.0 V 0.5 2.0 1 ILOAD = 1mA 100 nA 3 μA ♦ Note 1: SHDN must transition faster than 1V/100mS for proper operation. Date: 6/7/06 Rev B SP6648 Ultra-low Quiescent Current, High Efficiency Boost Regulator 2 © 2006 Sipex Corporation PIN DESCRIPTION PIN NUMBER PIN NAME 1 VBATT DESCRIPTION Battery Voltage. The startup circuitry is powered by this pin. Battery Voltage is used to calculate switch off time: tOFF = KOFF/ (VOUT - VBATT). When the battery voltage drops below 0.61V the SP6648 goes into an undervoltage lockout mode (UVLO), where the part is shut down. 2 LBI Low Battery Input. LBI below 0.61V causes the SP6648 pin to pull LBON pin down to ground. Use a resistor divider to program the low voltage threshold for a specific battery configuration. 3 LBON Low Battery Output Not. Open drain NMOS output that sinks current to ground when LBI is below 0.61V. 4 RLIM Current Limit Resistor. By connecting a resistor RLIM from this pin to ground the inductor peak current is set by IPEAK=1600/RLIM. The range for RLIM is 9kΩ (for 180mA) to 1.KΩ (for 1.6A). 5 SHDN Shutdown Not. Tie this pin high to VBATT, for normal operation. Pull this pin to ground to disable all circuitry inside the chip. In shutdown the output voltage will float down to a diode drop below the battery voltage. 6 FB Feedback. Connect this pin to GND for fixed +3.3V operation. Connect this pin to a resistor voltage divider between VOUT and GND for adjustable output operation. 7 GND 8 PGND 9 LX 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 the PGND pin. 10 VOUT Output Voltage. The inductor current flows out of this pin during switch off-time. It is also used as the internal regulator voltage supply. Connect this pin to the positive terminal of the output capacitor. Date: 6/7/06 Rev B Ground. Connect to ground plane. Power Ground. The inductor charging current flows out of this pin. SP6648 Ultra-low Quiescent Current, High Efficiency Boost Regulator 3 © 2006 Sipex Corporation FUNCTIONAL DIAGRAM VBATT LX QKILL charge end IUC VO undercurrent comparator SHDN SDI 0.61V + c - TOFF + Min TOFF - c VBATT INTERNAL VBATT INTERNAL SUPPLY UVLO VOUT QKILL R switch buffer Q PMOS VO VBATT CHARGE VO NMOS Max Ton n Ref Block SDI IBIAS 1.25V REF + - + - c VOLOW S LX Qn current reference VO FB 0.61V c FB RLIM + - LOAD c overcurrent comparator SWITCH GROUND Ipkset LBI current control current reference PGND INTERNAL GROUND 0.61V + GND LBON c SP6648 THEORY OF OPERATION Detailed Description Control Scheme The SP6648 is a step-up DC-DC converter that can start up with input voltages as low as 0.85V (typically) and operates with an input voltage down to 0.61V. Ultra low quiescent current of 12μA provides excellent efficiency, up to 94%. In addition to the main switch, a 0.3Ω internal MOSFET the SP6648 has an internal synchronous rectifier, increasing efficiency and reducing the space requirements of an external diode. An internal inductive-damping switch significantly reduces inductive ringing for low-noise, high efficiency operation. If the supply voltage drops below 0.61V the SP6648 goes into under voltage lock-out mode, thus opening both internal switches. An externally programmable low battery detector with open drain output provides the ability to flag a battery-low condition. The inductor peak current is externally programmable to allow for a range of inductor values. A minimum off-time, current limited pulse frequency modulation (PFM) control scheme combines the high output power and efficiency of a pulse width modulation (PWM) device with the ultra low quiescent current of the traditional PFM. At low to moderate output loads, the PFM control provides higher efficiency than traditional PWM converters are capable of delivering. At these loads, the switching frequency is determined by a minimum off-time (tOFF, MIN) and a maximum on-time (tON, MAX) where: Date: 6/7/06 Rev B tOFF ≥ KOFF / (VOUT - VBATT) and tON ≤ KON / VBATT with KOFF = 1.0Vμs and KON = 4.0Vμs. SP6648 Ultra-low Quiescent Current, High Efficiency Boost Regulator 4 © 2006 Sipex Corporation THEORY OF OPERATION: Continued At light loads (as shown in plot A in Figure 1) the charge cycle will last the maximum value for tON: For a 1V battery this would be as follows: Inductor Current vs. Load llim Ton Max. tON = KON / VBATT = 4.0Vμs / 1V = 4.0μs E Toff Min. E. Iripple=Toff* (Vo - Vi)/L llim Ton Max. The current built up in the coil during the charge cycle gets fully discharged in the discontinuous conduction mode (DCM). When the current in the coil has reached zero, the synchronous rectifier switch is opened and the voltage across the coil (from VBATT to LX) is shorted internally to eliminate inductive ringing. D Toff Min. D. Toff*= (Vo - Vi)/L