View SP7648TR_1315136.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

(R)
Preliminary
SP7648
Low Reference High Efficiency Boost Regulator
FEATURES True Shutdown 700mA Output Current at 3.3V Input; 4.2V output 92% Efficiency from 2.7VIN to 3.3VOUT Wide Input Voltage Range: 2.7V to 4.5V 5V Fixed or Adjustable Output 0.3 Switch Integrated Synchronous Rectifier:0.3 Anti-Ringing Switch Technology Programmable Inductor Peak Current Logic Shutdown Control Low 0.8V or 0.288V Reference Voltage Small 10 pin DFN or MSOP Package
VBATT 1 FLASH NC (Test) RLIM SHDN
2 3 4 5
10 V
OUT
SP7648
10 Pin DFN
9 LX 8P
GND
7 GND 6 FB
Now Available in Lead Free Packaging
APPLICATIONS LED Driver Camera Flash Handheld Portable Devices
DESCRIPTION The SP7648 is an ultra-low quiescent current, high efficiency step-up DC-DC converter ideal for single cell Li-Ion or dual cell alkaline battery applications to drive various LEDs. The SP7648 combines low quiescent current and excellent light-load efficiency of PFM control. The SP7648 features synchronous rectification, a 0.3 charging switch, an anti-ringing inductor switch, undervoltage lockout and programmable inductor peak current. The device can be shut down by a 1nA active LOW shutdown pin. A very low 0.288V reference voltage is optimized for driving a constant current load. TYPICAL APPLICATION CIRCUIT
4.7H VIN (2.7 - 4.5V) 10F VBATT ON/OFF SHDN RLIM RLIM 1.0K
(R)
SP7648
LX
VOUT NC 470pF 10F 0.33 D1 1K R2 R1
FLASH GND PGND FB
FLASH
Q1
Date: 7/20/05
SP7648 Ultra-low Quiescent Current, High Efficiency Boost Regulator
(c) Copyright 2005 Sipex Corporation
1
ABSOLUTE MAXIMUM RATINGS
LX, Vo, VBATT , FLASHOUT, FB to GND pin ...................... -0.3 to 6.0V SHDN, FLASH ..................................................... -0.3V to VBATT +1.0V Vo, GND, LX Current ....................................................................... 2A Reverse VBATT Current .............................................................. 220mA Forward VBATT Current .............................................................. 500mA Storage Temperature .................................................. -65 C to 150C Operating Temperature ................................................ -40C to +85C 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 = 3.6V, VFB=ZeroV, ILOAD = 0mA, TAMB= -40C to +85C, VOUT = 5.0V, typical values at 27C unless otherwise noted. The denotes the specifications which apply over full operating temperature range -40C to +85C, unless otherwise specified. PARAMETER Input Voltage Operating Range, VBATT Output Voltage Range, VOUT Under Voltage Lock-out/UVLO Output Voltage, VO Shutdown Current into VO, ISDO Shutdown Current into VBATT, ISDB Efficiency Inductor Peak Current Limit, IPK Output Current (Note 2) Minimum Off-Time Constant KOFF Maximum On-Time Constant KON Enable Valid to Output Stable (Note 3) NMOS Switch Resistance PMOS Switch Resistance FB Set Voltage, VFB FB Input Current SHDN Input Voltage (Note 1) VIL VIH SHDN Input Current LX Pin Leakage FLASH Threshold VIL VIH 650 0.5 2.0 0.76 0.266 2.0 1.0 MIN 2.7 2.7 0.5 4.6 TYP 0.61 5.0 1 250 92 800 1600 800 400 200 1.0 3.5 300 0.30 0.30 0.8 0.288 1 1 MAX 4.5 5.5 0.7 5.4 500 750 1000 1.5 5.0 500 0.6 0.6 0.84 0.310 100 0.5 100 3 0.4 UNITS V V V V nA nA % mA mA mA mA mA V*s V*s s V V nA V nA A V V Internal Feedback Divider VSHDN = ZeroV VSHDN = ZeroV, VBATT = 2.7V VBATT = 2.7V, IOUT = 200mA, RLIM = 2k RLIM = 2k, IPK = 1600/RLIM RLIM = 1k, IPK = 1600/RLIM VBATT = 2.7V, RLIM =1k VBATT = 2.7V, RLIM =2k VBATT = 2.7V, RLIM = 4k KOFF TOFF (VOUT - VBATT) KON TON (VBATT) ILOAD = 1mA INMOS = 100mA IPMOS = 100mA External feedback Flash = 0 External feedback Flash = 1 VFB =1.3V VBATT = 2.7V VBATT = 2.7V CONDITIONS After Startup
Note 1: SHDN must transition faster than 1V/100mS for proper operation. Note 2: Output Current I = VIN { VOUT } X Efficiency x {Inductor Peak Current - Inductor Ripple Current} 2
Note 3: Guaranteed by Design.
Date: 7/20/05
SP7648 Ultra-low Quiescent Current, High Efficiency Boost Regulator
(c) Copyright 2005 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 SP7648 goes into an undervoltage lockout mode (UVLO), where the part is shut down. Reference Control Input. Internal Reference defaults to 0.8V if FLASH = LOW and 0.288V if FLASH = HIGH. No connection. This pin is bonded out for test purposes only and must be left floating in all applications. 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 9k (for 180mA) to 1.K (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. Feedback. Connect this pin to GND for fixed +5V 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
FLASH
3
NC (Test)
4
RLIM
5
SHDN
6
FB
7 8 9
GND PGND LX
10
VOUT
Date: 7/20/05
SP7648 Ultra-low Quiescent Current, High Efficiency Boost Regulator
(c) Copyright 2005 Sipex Corporation
3
FUNCTIONAL DIAGRAM
Date: 7/20/05
SP7648 Ultra-low Quiescent Current, High Efficiency Boost Regulator
(c) Copyright 2005 Sipex Corporation
4
THEORY OF OPERATION
_________________________DETAILED DESCRIPTION The SP7648 is a step-up DC-DC converter with an input voltage operation range from 2.7V to 4.7V. In addition to the main 0.3 internal NMOSFET switch the SP7648 has an internal synchronous rectifier, thereby increasing efficiency and reducing the space and cost 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 SP7648 goes into under voltage lockout, thus opening both internal switches. The inductor peak current is externally programmable to allow for a range of inductor values.
devices, the inductor and input & output filter 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 SP7648 devices as possible (within 0.2in or 5mm). The DC-DC converter and any digital circuitry should be placed on the opposite 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 voltagefeedback VFB node and separated from it using grounded copper to minimize EMI. See the SP7648EB Evaluation Board Manual for PC Board Layout design details.
__________________________ CIRCUIT LAYOUT Printed circuit board layout is a critical part of a power supply design. Poor designs can result in excessive EMI on the feedback paths and on the ground planes with applications 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 integrated into ground as a pseudoground 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 SP7648
________________ 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) TON > KON / VBATT KOFF = 1.0Vs KON = 3.5 Vs
Date: 7/20/05
SP7648 Ultra-low Quiescent Current, High Efficiency Boost Regulator
(c) Copyright 2005 Sipex Corporation
5
THEORY OF OPERATION At light loads (as shown in plot A in Figure 1) the charge cycle will last the maximum value for tON: For a 3V battery this would be as follows: TON = KON / VBATT = 3.5VS/ 3V = 1.17S. 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. 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 SP7648 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 which ends the charge cycle and starts the discharge cycle. However, full load is not yet achieved because at the end of the minimum discharge time the output was still within regulation. Maximum load is reached when this discharge time has shrunk to the minimum allowed value TOFF as shown in Plot E of Figure 1. _____________________ COMPONENT SELECTION Selection of capacitors for SP7648 power supply circuits can be made through the use of the Component Selection Table. Capacitor equivalent series resistance (ESR) in the range of 0.2 to 0.3 is a requirement for obtaining sufficient output voltage ripple for the SP7648 to properly regulate under its load. For example, in the SP7648 application circuit a 10F, 10V, X5R, surface mount ceramic output filter capacitor is used. Ceramic capacitors have an ESR too low to produce enough output ripple for the SP7648 to regulate the output; therefore, a 0.33 resistor is added in series with the 10F capacitor at the VOUT pin. Designers should select input and output capacitors with a rating exceeding the inductor current ripple, which is typically set by the inductor value and the KON value as given in the following relationship: IL(RIPPLE) = KON/L, where KON = 3.5V*S
Inductor Current vs. Load
llim Ton Max. Toff Min. E. Iripple=Toff* (Vo - Vi)/L llim Ton Max. Toff Min. D. Toff*= (Vo - Vi)/LE
D
C
llim Ton Max. Toff Min. B. Iripple=Ton*Vi/L
B
llim Ton Max. Toff Min. A. Iripple=Ton*Vi/L
A
Figure 1. Inductor Current vs. Load
Date: 7/20/05
SP7648 Ultra-low Quiescent Current, High Efficiency Boost Regulator
(c) Copyright 2005 Sipex Corporation
6
THEORY OF OPERATION
INDUCTORS - SURFACE MOUNT Inductor Specification Series R Isat Size LxWxH Inductor Type ohms (A) (mm) Wurth Elektronik 744042004 0.070 1.70 4.8x4.8x1.8 Shielded Ferrite Core TDK SLF6025T-4R7M1R5-PF 0.031 1.50 6.0x6.0x2.5 Shielded Ferrite Core Coilcraft MSS6122-4R7MX 0.065 1.85 6.1x6.1x2.2 Shielded Ferrite Core Wurth Elektronik 744042006 0.080 1.50 4.8x4.8x1.8 Shielded Ferrite Core TDK SLF6025T-6R8M1R3-PF 0.044 1.30 6.0x6.0x2.5 Shielded Ferrite Core Coilcraft MSS6122-6R8MX 0.100 1.45 6.1x6.1x2.2 Shielded Ferrite Core CAPACITORS - SURFACE MOUNT Capacitor Specification Capacitance Manufacturer/Part No. ESR Ripple Current Size LxWxH Voltage Capacitor (uF) ohms (max) 10C Rise (A) (mm) (V) Type 10 TDK C2012X5R0J106M 0.020 1.70 2.0x1.2x1.35 6.3 X5R Ceramic 10 Murata GRM21BR60J106KE19L 0.020 1.70 2.0x1.2x1.35 6.3 X5R Ceramic MOSFETS - SURFACE MOUNT MOSFET Specification MOSFET Manufacturer/Part No. RDS(on) Id Package MOSFET type ohms (A) Size Specifications NMOS Vishay Si1400DL 0.190 1.70 SC70-6 20V, Vgs = 2.5V, Pd = 0.5W 30V, Vgs = 2.5V, Pd = 0.5W NMOS Fairchild FDN337N 0.070 2.20 SOT23-3 RESISTORS - LOW VALUE SURFACE MOUNT Resistor Specification Resistor Manufacturer/Part No. Resistance Pd Package Resistor Ref. Des. ohms (W) Size Specifications Rc, R2 Vishay CRCW0603R33F 0.33 0.10 0603 Thick Film 1% or 5% Rc, R2 Vishay CRCW0603R22F 0.22 0.10 0603 Thick Film 1% or 5% Note: Components highlighted in bold are those used on the SP7648EB Evaluation Board. Inductance (uH) 4.7 4.7 4.7 6.8 6.8 6.8 Manufacturer/Part No. Manufacturer Website
www.we-online.de www.tdk.com www.coilcraft.com www.we-online.de www.tdk.com www.coilcraft.com
Manufacturer Website
www.tdk.com www.murata.com
Manufacturer Website
www.vishay.com www.fairchildsemi.com
Manufacturer Website
www.vishay.com www.vishay.com
Table 1: Component Selection
For the example, a 10H inductor would have an inductor current ripple of 350mA, while a 4.7H inductor would have an inductor current ripple value of 740mA. Do not allow tantalum capacitors to exceed their ripple-current ratings. An input filter capacitor can reduce peak currents drawn from the battery and improve efficiency. For most applications, use the same capacitor for the input and output. Low-ESR tantalum capacitors are acceptable provided they meet the ESR requirement of 0.2 to 0.3. In selecting an inductor, the saturation current specified for the inductor needs to be greater than the SP7648 peak current to avoid saturating the inductor, which would result in a loss of efficiency and could damage the inductor. The SP7648 evaluation board uses a Wurth 4.7H inductor with an ISAT value of 1.7A and a DCR of 0.065, which handles the IPEAK of 1.6A of the SP7648 and will deliver high efficiencies. Other inductors could be selected provided their ISAT is greater than the IPEAK of the SP7648.
______________ VOUT PROGRAMMING The SP7648 can be programmed as either a voltage source or a current source. To program the SP7648 as voltage source, the SP7648 requires 2 feedback resistors R1 & R2 to control the output voltage. To set VOUT in the voltage mode, use the equation: R1 = [(VOUT/0.8)-1] * R2, where flash < 0.4V, R1 = [(VOUT/0.288)-1] * R2, where flash > 1.0V _______________________ USING THE RLIM FUNCTION The peak inductor current, IPEAK, is programmed externally by the RLIM resistor connected between the RLIM pin and GND. The peak inductor current is defined by: IPEAK = 1600/RLIM The saturation current specified for the inductor needs to be greater than the peak
Date: 7/20/05
SP7648 Ultra-low Quiescent Current, High Efficiency Boost Regulator
(c) Copyright 2005 Sipex Corporation
7
THEORY OF OPERATION the LED. To set the operating current to be about 200mA in torch mode, the flash pin is forced low, R2 is selected as 0.8V/ 0.2 = 4, as shown in the typical application circuit. To set the operating current to 700mA in flash mode, the flash pin is forced high, R is selected as 0.288V/0.41 = 700mA. In reality R in Flash includes the series MOSFET RDSON and the parallel combination of R2 = 4 shown by the formula: R in Flash = The SP7648 will regulate the output by the equations above depending on the state of the FLASH pin. When the FLASH pin is low (<0.4V), the internal reference voltage is defined as 0.8V. When the FLASH pin is high (>0.4V), the internal reference voltage is defined as 0.288V. This allows the use of smaller values for the sense resistor for current regulation mode. This improves efficiency and reduces the physical size of the sense resistor. An external MOSFET switch can be used to change the sense resistor when changing to the Flash Mode. {R1 X (R2 + Q1RDSON)} {R1 + R2 + Q1RDSON}
current to avoid saturating the inductor, which would result in a loss in efficiency and could damage the inductor. The SP7648 evaluation board uses a RLIM value of 1K for an IPEAK = 1.6A to allow the circuit to deliver up to 700mA for VIN = 3.3V and VOUT = 4.2V. Other values could be selected using the above relationships. _________________USING THE FLASH CONTROL PIN
If the SP7648 is powered up before the LED is plugged in, the circuit will bring the feedback pin to ZeroV and the SP7648 has a feature to set the output voltage to be 5V. Once the LED is plugged in, the feedback pin will go up to 0.8V in torch mode or 0.288V in flash mode and begin to regulate. The output voltage will go from 5V to VF+VFB, where VF is the forward voltage of the LED. When the LED is open, the feedback pin voltage will go to ZeroV and the output voltage will go to 5V which will protect the part from overvoltage at the output. One approach to control LED brightness is to apply a PWM signal to the SHDN input of the SP7648. In this case, the output current will be equal to the product of VREF/R1 and the average duty cycle at the SHDN pin. An optional 10K potentiometer may also be used for dimming the LED current by varying the potentiometer between low brightness and full brightness. If the FB pin is pulled below 150mV the output will default to 5V defined by an internal resistor divider.
________________ HIGH BRIGHTNESS WHITE LED For the high brightness LumiLED white LED application, the SP7648 is generally programmed as a current source. The bias resistors R1 and R2 are used to set the operating current of the white LED with the equation:
R = VFB/IF
where VFB is 0.8V in torch mode and 0.288V in flash mode, IF is the operating current of
Date: 7/20/05
SP7648 Ultra-low Quiescent Current, High Efficiency Boost Regulator
(c) Copyright 2005 Sipex Corporation
8
TYPICAL PERFORMANCE CHARACTERISTICS
800
SP7648 for Luxeon I
100 90
SP7648 for Luxeon I
Flash Mode, Vf=3.6V Torch Mode, Vf=3.2V
Output current (mA)
700
500 400 300 200 100 0 3.0 3.2 3.4 3.6
Flash Mode, Vf=3.6V Torch Mode, Vf=3.2V
Efficiency (%)
4.0 4.2
600
80 70
60 50
3.8
3.0
3.2
3.4
Vin (V)
3.6 Vin (V)
3.8
4.0
4.2
800
SP7648 for AOT(2015HPW1915B)
100 90
SP7648 for AOT(2015HPW1915B)
Flash Mode, Vf=3.9V Torch Mode,Vf=3.3V
Output current (mA)
700
500 400 300 200 100 0 3.0 3.2 3.4 3.6 3.8 4.0 4.2
Flash Mode, Vf=3.9V Torch Mode, Vf=3.3V
Efficiency (%)
600
80 70 60 50 3.0 3.2 3.4 3.6 3.8 4.0 4.2
Vin (V)
Vin (V)
600
SP7648 for AOT(6060HPW0305BD)
100 90
SP7648 for AOT(6060HPW0305BD)
Flash Mode, Vf=4.2V Torch Mode, Vf=3.5V
Output current (mA)
500 400 300 200 100 0 3.0 3.2 3.4 3.6 3.8 4.0 4.2
Flash Mode, Vf=4.2V Torch Mode, Vf=3.5V
Efficiency (%)
80 70 60 50 3.0 3.2 3.4
3.6
3.8
4.0
4.2
Vin (V)
Vin (V)
Date: 7/20/05
SP7648 Ultra-low Quiescent Current, High Efficiency Boost Regulator
(c) Copyright 2005 Sipex Corporation
9
TYPICAL PERFORMANCE CHARACTERISTICS
Ch1 = SHDN (5V/div) Ch2 = Vout (1V/div)
Ch4 = Iin (1A/div)
Startup 200mA Torch, Vin = 3.6V, Vout = 3.9V
Startup 700mA Flash, Vin = 3.6V, Vout = 3.65V
Ch1 = Vin (AC) 100mV/div
Ch2 = Vout (AC) 100mV/div
Ripple 200mA Torch, Vin = 3.6V, Vout = 3.9V
Ripple 700mA Flash, Vin = 3.6V, Vout = 3.65V
Date: 7/20/05
SP7648 Ultra-low Quiescent Current, High Efficiency Boost Regulator
(c) Copyright 2005 Sipex Corporation
10
PACKAGE: 10 PIN DFN
10-PIN 3X3MM DFN PACKAGE OUTLINE
JEDEC DOCUMENT MO-229 VARIATION VEED-5 DIMENSIONS IN MILLIMETERS SYMBOL A A1 A3 b e D E D2 E2 L K N ND 2.20 1.40 0.30 0.20 0o 0.18 (CONTROLLING UNIT) MINIMUM 0.80 0.00 NOMINAL 0.90 0.02 0.20 REF 0.25 0.50 BSC 3.00 BSC 3.00 BSC --0.40 --10 5 2.70 1.75 0.50 -14o 0.087 0.055 0.012 0.008 0o MAXIMUM 1.00 0.05 0.30 DIMENSIONS IN INCHES (CONVERT UNIT 1MM = 0.0394INCH) MINIMUM 0.032 0.000 0.007 NOMINAL 0.035 0.001 0.008 REF 0.010 0.020 BSC 0.118 BSC 0.118 BSC --0.016 --10 5 0.106 0.069 0.020 -14o MAXIMUM 0.039 0.002 0.012
NOTE 1: PIN #1 INDICATOR MUST BE WITHIN THIS AREA AND CAN BE ANY SHAPE
Date: 7/20/05
SP7648 Ultra-low Quiescent Current, High Efficiency Boost Regulator
(c) Copyright 2005 Sipex Corporation
11
ORDERING INFORMATION
Part Number Operating Temperature Range Package Type
SP7648ER .................................................. -40C to +85C ........................................................... 10 Pin DFN SP7648ER/TR ............................................ -40C to +85C .......................................................... 10 Pin DFN SP7648EU .................................................. -40C to +85C ........................................................ 10 Pin MSOP SP7648EU/TR ............................................ -40C to +85C ....................................................... 10 Pin MSOP Available in lead free packaging. To order add "-L" suffix to part number. Example: SP7648ER/TR = standard; SP7648ER-L/TR = lead free /TR = Tape and Reel Pack quantity is 2,500 for DFN and MSOP.
CLICK HERE TO ORDER SAMPLES
Corporation
ANALOG EXCELLENCE
Sipex Corporation Headquarters and Sales Office 233 South Hillview Drive Milpitas, CA 95035 TEL: (408) 934-7500 FAX: (408) 935-7600
Sales Office 22 Linnell Circle Billerica, MA 01821 TEL: (978) 667-8700 FAX: (978) 670-9001 e-mail: sales@sipex.com
Sipex Corporation reserves the right to make changes to any products described herein. Sipex does not assume any liability arising out of the application or use of any product or circuit described herein; neither does it convey any license under its patent rights nor the rights of others.
Date: 7/20/05
SP7648 Ultra-low Quiescent Current, High Efficiency Boost Regulator
(c) Copyright 2005 Sipex Corporation
12

▲Up To Search▲

Price & Availability of SP7648TR

	To Download SP7648TR Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .