SP6648

® 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 Voltage Range: 0.95V 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 LBI LBON RLIM SHDN 1 2 3 4 5 SP6648 10 Pin DFN 10 V OUT 9 LX 8P GND 7 GND 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, PDA’s, MP3 players, and other portable devices. The SP6648 combines the high delivery associated with PWM control, and 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 + 47µF 1 LBI LBON 2 3 4 SHDN 1.87K VBATT LBI LBON RLIM VOUT 10 + 1µF 205K 47pF 47µF 3.3VOUT Io (mA) 450 400 350 SP6648 LX 9 PGND 8 GND 7 FB 6 300 250 200 150 100 Vout=3.3V, Ipk=0.85A 50 0 Vout=5.0V, Ipk=0.85A 1.5 2.0 2.5 3.0 Vin (V) 3.5 4.0 4.5 5 SHDN 124K 1.0 Maximum Load Current in Operation Date: 7/19/04 SP6648 Ultra-low Quiescent Current, High Efficiency Boost Regulator © Copyright 2004 Sipex Corporation 1 ABSOLUTE MAXIMUM RATINGS 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 Operating Temperature ................................................ -40°C to +85°C Lead Temperature (Soldering, 10 sec) ....................................... 300 °C ESD Rating ........................................................................ 1.5kV HBM 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=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 Input Voltage Operating Range, VBATT Output Voltage Range, VOUT Start-up Input Voltage, VBATT Under Voltage Lock-out/UVLO Output Voltage, VO Quiescent Current into VO, IQO Quiescent Current into VBATT, IQB Shutdown Current into VO, ISDO Shutdown Current into VBATT, ISDB Efficiency Inductor Current Limit, IPK = 1600/RLIM 650 1300 0.5 3.12 MIN 0.7 2.5 0.85 0.61 3.30 12 250 1 250 84 92 800 1600 100 200 150 400 Minimum Off-Time Constant KOFF Maximum On-Time Constant KON Enable Valid to Output Stable NMOS Switch Resistance PMOS Switch Resistance FB Set Voltage, VFB FB Input Current LBI Falling Trip Voltage LBI Hysteresis 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 0.56 1.19 0.5 2.5 1.0 4.0 300 0.30 0.30 1.25 1 0.61 25 0.4 1 0.25 1.0 0.5 2.0 1 100 3 nA µA V 1.5 5.5 500 0.6 0.6 1.31 100 0.66 1000 2000 TYP MAX 4.5 5.5 1.1 0.7 3.48 25 750 500 750 UNITS V V V V V µA nA nA nA % % mA mA mA mA mA mA V*µs V*µs µs Ω Ω V nA V mV V µA ♦ ♦ ♦ ♦ ♦ ♦ ♦ VBATT = 1.3V, ISINK = 1mA VBATT = 1.3V, VLBON = 3.3V VBATT = 1.3V VBATT = 1.3V VBATT = 2.6V VBATT = 2.6V ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ Internal Feedback Divider VOUT = 3.3V, VFB = 1.5V, Toggle SHDN VOUT = 3.3V, VFB = 1.5V VSHDN = 0V VSHDN = 0V, VBATT = 2.6V VBATT = 1.3V, IOUT = 100mA, RLIM =2kΩ VBATT = 2.6V, IOUT = 200mA, RLIM =2kΩ RLIM = 2kΩ RLIM = 1kΩ VBATT = 1.3V, RLIM = 4kΩ VBATT = 2.6V, RLIM = 4kΩ VBATT = 1.3V, RLIM =2kΩ VBATT = 2.6V, RLIM =2kΩ KOFF ≤ TOFF (VOUT- VBATT) KON ≥ TON (VBATT) ILOAD = 1mA INMOS = 100mA IPMOS = 100mA External feedback VFB =1.3V RLOAD = 3kΩ CONDITIONS After Startup Output Current Note 1: SHDN must transition faster than 1V/100mS for proper operation. Date: 7/19/04 SP6648 Ultra-low Quiescent Current, High Efficiency Boost Regulator © Copyright 2004 Sipex Corporation 2 PIN DESCRIPTION PIN NUMBER 1 PIN NAME 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. 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. Low Battery Output Not. Open drain NMOS output that sinks current to ground when LBI is below 0.61V. 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). 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. 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. Ground. Connect to ground plane. Power Ground. The inductor charging current flows out of this pin. 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. 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. 2 LBI 3 LBON 4 RLIM 5 SHDN 6 FB 7 8 9 GND PGND LX 10 VOUT Date: 7/19/04 SP6648 Ultra-low Quiescent Current, High Efficiency Boost Regulator © Copyright 2004 Sipex Corporation 3 FUNCTIONAL DIAGRAM VBATT QKILL LX charge end VO IUC undercurrent comparator Min TOFF UVLO R Q CHARGE switch buffer INTERNAL VBATT VBATT + INTERNAL SUPPLY TOFF c VOUT SHDN SDI 0.61V + c QKILL PMOS VBATT NMOS VO Max Ton VO n SDI Ref Block IBIAS 1.25V REF FB 0.61V + c + c VOLOW S Qn LX current reference + c LOAD VO overcurrent comparator FB RLIM LBI 0.61V Ipkset current control current reference SWITCH GROUND INTERNAL GROUND PGND GND LBON + c SP6648 THEORY OF OPERATION Detailed Description 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 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 lockout, thus opening both internal switches. An externally programmable low battery detector with open drain output provides the ability to flag battery low condition. The inductor peak current is externally programmable to allow for a range of inductor values. Date: 7/19/04 Control Scheme 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: 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 © Copyright 2004 Sipex Corporation 4 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: tON = KON / VBATT = 4.0Vµs / 1V = 4.0µs The current built up in the coil during the charge cycle gets fully discharged (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. With increasing load (as shown in plot B in Figure 1) this inductor damping time becomes shorter, because the output will quickly drop below its regulation point due to heavier load. If the load current increases further the SP6648 enters continuous conduction mode (CCM) where there is always current flowing in the inductor. The charge time remains at maximum tON as long as the inductor peak current limit is not reached as shown in plot C in Figure 1. The inductor peak current limit can be programmed by tying a resistor RLIM from the RLIM pin to ground where: IPEAK = 1600 / RLIM When the peak current limit is reached the charge time is short-cycled. In plot D of Figure 1, the switch current reaches the peak current limit during the charge period Ton Max. Inductor Current vs. Load llim Ton Max. Toff Min. E. Iripple=Toff* (Vo - Vi)/L llim Toff Min. D. Toff*= (Vo - Vi)/L