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SP6648
Ultra-low Quiescent Current, High Efficiency Boost Regulator
FEATURES Ultra-low 12A 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: 0.3 0.3 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 12A quiescent current, synchronous rectification, a 0.3 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
10H VBATT + 47F 1 LBI LBON 2 3 4 SHDN 1.87K VBATT LBI LBON RLIM VOUT 10 + 1F 205K 47pF 47F 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 (c) 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 150C Operating Temperature ................................................ -40C to +85C 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= -40C to +85C, VOUT = +3.3V, typical values at 27C unless otherwise noted. The denotes the specifications which apply over full operating temperature range -40*C to +85C, 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 A 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 A nA nA nA % % mA mA mA mA mA mA V*s V*s s V nA V mV V A 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 =2k VBATT = 2.6V, IOUT = 200mA, RLIM =2k RLIM = 2k RLIM = 1k VBATT = 1.3V, RLIM = 4k VBATT = 2.6V, RLIM = 4k VBATT = 1.3V, RLIM =2k VBATT = 2.6V, RLIM =2k KOFF TOFF (VOUT- VBATT) KON TON (VBATT) ILOAD = 1mA INMOS = 100mA IPMOS = 100mA External feedback VFB =1.3V RLOAD = 3k 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
(c) 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 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. 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
(c) Copyright 2004 Sipex Corporation
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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 12A provides excellent efficiency, up to 94%. In addition to the main switch, a 0.3 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 = 1.0Vs and KON = 4.0Vs.
SP6648 Ultra-low Quiescent Current, High Efficiency Boost Regulator
(c) 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 = 4.0Vs / 1V = 4.0s 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)/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
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.
Date: 7/19/04
SP6648 Ultra-low Quiescent Current, High Efficiency Boost Regulator
(c) Copyright 2004 Sipex Corporation
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TYPICAL PERFORMANCE CHARACTERISTICS Refer to the Typical Application Circuit on page 1, TAMB=+25C.
100 95 90
100 95 90
Efficiency (%)
Vi=3.0V Vi=2.6V Vi=2.0V Vi=1.3V Vi=1.0V 0.1 1.0 10.0 Iload (mA) 100.0 1000.0
85 Efficiency (%) 80 75 70 65 60
85 80 75 70 65 60 0.1 1.0 10.0 Iload (mA) 100.0 1000.0
Vi=4.2V Vi=3.2V Vi=2.6V Vi=2.0V Vi=1.6V Vi=1.0V
Efficiency vs. Load Current, VOUT=3.3V
3.400 3.380 3.360 3.340 3.320
VOUT (V)
Efficiency vs. Current Load, VOUT=5.0V
Vi=3.0V Vi=2.6V Vi=2.0V Vi=1.3V Vi=1.0V
5.100 5.080 5.060 5.040 5.020
Vout (V)
Vi=4.2V Vi=3.2V Vi=2.6V Vi=2.0V Vi=1.6V Vi=1.0V
3.300 3.280 3.260 3.240 3.220 3.200 0 100 200 300 400 500
ILOAD(mA)
5.000 4.980 4.960 4.940 4.920 4.900 0 100 200 300 400 500
Iload (mA)
Line/Load Rejection vs. Load Current, VOUT = 3.3V
100
Line/Load Rejection vs. Load Current, VOUT = 5.0V
300
80
250
200
Iin (uA)
Iin (uA)
60
150
40
100
20
50
0 1.0 1.5 2.0 Vin (V) 2.5 3.0
0 1.0 1.5 2.0 2.5 3.0 Vin (V) 3.5 4.0 4.5
No Load Battery Current, VOUT=3.3V
Date: 7/19/04
No Load Battery Current, VOUT=5.0V
(c) Copyright 2004 Sipex Corporation
SP6648 Ultra-low Quiescent Current, High Efficiency Boost Regulator
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TYPICAL PERFORMANCE CHARACTERISTICS: Continued Refer to the Typical Application Circuit on page 1, TAMB=+25C.
400 350 300
350 500 450 400
250 Io (mA) 200 150 100
Io (mA)
300 250 200 150 100
50
50
0 1.0 1.5 2.0 Vin (V) 2.5 3.0
0 1.0 1.5 2.0 2.5 3.0 Vin (V) 3.5 4.0 4.5
Maximum Resistive Load Current in Startup, VOUT=3.3V
Maximum Resistive Load Current in Startup, VOUT=5.0V
VOUT (AC)
VOUT (AC)
Inductor Current (0.2A/DIV)
Inductor Current (0.2A/DIV)
Output Ripple, VIN=2.6V, ILOAD=200mA, VOUT=3.3V
5.0
Output Ripple, VIN=2.6V, ILOAD=200mA, VOUT=5.0V
5.0
4.0
4.0
Kon (V*usec)
Kon (V*usec)
3.0
3.0
2.0
2.0
1.0
1.0
0.0 0.9
1.2
1.5
1.8
2.1 2.4 Vin (V)
2.7
3.0
3.3
0.0 0.9
1.4
1.9
2.4
2.9 3.4 Vin (V)
3.9
4.4
4.9
KON vs. VIN , VOUT=3.3V
KON vs. VIN , VOUT=5.0V
Date: 7/19/04
SP6648 Ultra-low Quiescent Current, High Efficiency Boost Regulator
(c) Copyright 2004 Sipex Corporation
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TYPICAL PERFORMANCE CHARACTERISTICS: Continued Refer to the Typical Application Circuit on page 1, TAMB=+25C.
2.0
2.0
1.5 Koff (V*usec)
Koff (V*usec)
1.5
1.0
1.0
0.5
0.5
0.0 0.9
1.2
1.5
1.8
2.1 2.4 Vin (V)
2.7
3.0
3.3
0.0 0.9
1.4
1.9
2.4
2.9 3.4 Vin (V)
3.9
4.4
4.9
KOFF vs. VIN , VOUT=3.3V
KOFF vs. VIN , VOUT=5.0V
VIN
VOUT
VIN
VOUT
IIN (1A/div)
IIN(1A/div)
Startup, VIN=2.6V, VOUT=3.3V, RLOAD = 100
Startup, VIN=4.2V, VOUT=5.0V, RLOAD = 100
VOUT(AC)
VOUT (AC)
LX
LX
IOUT(0.2A/div)
IOUT (0.5A/DIV)
Load Step, 0.1A to 0.3A, VIN = 2.6V, VOUT = 3.3V
Date: 7/19/04
Load Step, 0.3A to 0.5A, VIN = 4.2V, VOUT = 5.0V
(c) Copyright 2004 Sipex Corporation
SP6648 Ultra-low Quiescent Current, High Efficiency Boost Regulator
8
APPLICATIONS INFORMATION
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 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 SP6648 devices, the inductor and input and 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 SP6648 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 voltage-feedback VOUT node and separated from it using grounded copper to minimize EMI. See the SP6648EB Evaluation Board Manual for PC Board Layout design details.
Component Selection
ripple for the SP6648 to regulate the output. 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 For the example of the 10H inductor the inductor current ripple would be 330mA, while for the 22H inductor the inductor current ripple value would be 150mA. 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 47F tantalum capacitor as used for the input. Low-ESR aluminum electrolytic capacitors are acceptable provided they meet the ESR requirement of 0.2 to 0.3, and we list an appropriate 100F aluminum electrolytic in the component selection table, but standard aluminum electrolytic capacitors are not recommended. In selecting an inductor, the saturation current specified for the inductor needs to be greater then the SP6648 peak current to avoid saturating the inductor, which would result in a loss in efficiency and could damage the inductor. The SP6648 evaluation board uses a Sumida CDRH5D28 10H inductor with an ISAT value of 1.3A and a DCR of 0.065, which easily handles the IPEAK of 0.85A of the SP6648 and will deliver high efficiencies. Other inductors could be selected provided their ISAT is greater than the IPEAK of the SP6648.
Selection of capacitors for SP6648 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 SP6648 to properly regulate under load. For ESR values in this range, low ESR Tantalum capacitors are recommended. For example, in the SP6648 application circuit a 47F, 10V, low-ESR, surfacemount tantalum output filter capacitor typically provides 50mV output ripple when stepping up from 2.6V to 3.3V at 200mA. Ceramic capacitors have ESR too low to produce enough output
Date: 7/19/04
SP6648 Ultra-low Quiescent Current, High Efficiency Boost Regulator
(c) Copyright 2004 Sipex Corporation
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APPLICATIONS INFORMATION: Continued
INDUCTORS - SURFACE MOUNT
Inductor Specification Inductance (H) 10 10 10 22 22 22 Manufacturer/Part No. Sumida CDRH5D28-100 TDK RLF5018T-100MR94 Sumida CD43-100 Sumida CDRH5D28-220 TDK RLF5018T-220MR63 Sumida CD43-220 Series R ISAT (A) 1.30 0.94 1.04 0.90 0.63 0.68 Size LxWxH (mm) 5.7x5.5x3.0 5.6x5.2x2.0 4.0x4.5x3.5 5.7x5.5x3 5.6x5.2x2.0 4.0x4.5x3.5 Intuctor Type Shielded Ferrite Core Shielded Ferrite Core Unshileded Ferrite Core Shileded Ferrite Core Shielded Ferrite Core Unshielded Ferrite Core Manufacturer Website www.sumida.com www.tdk.com www.sumida.com www.sumida.com www.tdk.com www.sumida.com
0.065 0.067 0.180 0.122 0.067 0.378
CAPACITORS - SURFACE MOUNT & LEADED
Capacitor Specification Capacitance Manufacturer Part No. (F) 47 47 100 Kemet T494C476K010AS Kemet T494V476K010AS Sanyo 25MV100AX ESR Ripple Current (A) @ 85C 1.06 0.99 0.30 Size LxWxH (mm) 6.0x3.2x2.5 7.3x4.3x2.0 6.3DX11L Voltage (V) 10 10 25 Capacitor Type SMT Tantalum SMT Tantalum Manufacturer Website www.kemet.com www.kemet.com
(max)
0.300 0.300 0.220
Radial Al Electrolytic www.sanyovideo.com
Note: Components highlighted in bold are those used on the SP6648EB Evaluation Board.
Component Selection Table
VBATT
C1 + 47F
L1 10H R5 1.0M
R3 549K
U1 SP6648
1 VBATT LBI LBON RLIM SHDN VOUT LX PGND GND FB 10 9 8 7 6
3.3VOUT
C4 1F
R4 LBON 249K
2 3 4 5
R1 205K
C3 47pF
+ C2 47F
RLIM 1.87K
R2 124K
SP6648EB Evaluation Board Schematic
Date: 7/19/04
SP6648 Ultra-low Quiescent Current, High Efficiency Boost Regulator
(c) Copyright 2004 Sipex Corporation
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APPLICATIONS INFORMATION : Continued
VOUT Programming
The SP6648 can be programmed as either a voltage source or a current source. To program the SP6648 as voltage source, the SP6648 requires 2 feedback resistors R1 & R2, as shown in the SP6648EB evaluation board schematic, to control the output voltage. To set VOUT in the voltage mode, use the equation: R1 = [(VOUT/1.25)-1] * R2
Using the RLIM Function
output goes low as determined by the relationship: VLOWBATT = 0.61 * [(R3 + R4)/R4] The SP6648 evaluation board R3 & R4 resistors have been set to trip for a falling battery threshold of about 2.0V. Using this relationship, other low battery threshold values can be set by the user.
UVLO the Under Voltage Lock-Out 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 current to avoid saturating the inductor, which would result in a loss in efficiency and could damage the inductor. The SP6648 evaluation board uses a RLIM value of 1.87K for an IPEAK = 850mA to allow the circuit to deliver up to 180mA for 1.3V input and 400mA for 2.6V input. Other values could be selected using the above relationships.
Using the LBON - Low Battery Output Function
Once started up, the SP6648 will regulate the output until the input battery is completely discharged or until the under voltage lock-out (UVLO) occurs at VBATT = 0.61V. The UVLO function will completely open all switches until the battery again rises above the 0.61V threshold.
Maximum Startup Current
The SP6648 will regulate the output until the input battery is completely discharged or until the under voltage lock-out (UVLO) occurs at VBATT = 0.61V. To provide a low battery warning, the Low Battery Output function of the SP6648 can be used. LBON is programmed externally by the R3 and R4 resistor divider connected between VBATT , the LBI input pin and GND. The LBON is an open drain output, which is active low and is pulled up by a 1M resistor R5 to VOUT. When the LBI comparator falling threshold of 0.61V is reached, the LBON
It should be noted that for low input voltages the SP6648 startup circuit can not support large load currents at startup. In startup the SP6648 needs to boost the output from zero volts using the input voltage. Once the output is greater than 1.9V the operate circuit takes over and the SP6648 can supply much more current. Curves of maximum load current in startup for the SP6648 are shown in the typical performance characteristics and can be compared with the page one curve for maximum load current in operation. For 1-cell battery applications, it is recommended to apply any large load current after the SP6648 has started up, typically in a few milliseconds. This is typically not a problem in many applications where the load is a processor whose load current is low until the processor voltage comes up.
Date: 7/19/04
SP6648 Ultra-low Quiescent Current, High Efficiency Boost Regulator
(c) Copyright 2004 Sipex Corporation
11
APPLICATIONS INFORMATION
SP6648LEDEB Evaluation Board with LumiLED High Brightness White LED
For the high brightness LumiLED white LED application, the SP6648 is generally programmed as a current source. The bias resistor Rb is used to set the operating current of the white LED as equation: Rb = VREF/IF
where VREF is around 0.61V, IF is the operating current of the LumiLED. To set the operating current to be about 350mA, Rb is selected as 1.8 as shown in the following schematic. The efficiency of the SP6648 LumiLED circuit is improved by the use of a silicon diode D1 and resistor R1 to set the voltage at the current sense resistor R2 to 0.61V instead of the higher 1.25V at the FB pin. An efficiency curve follows showing the SP6648 efficiency driving 350mA output current into the high brightness LumiLED.
VBATT
1.8-3.2V C1 10F
L1 10H
Important: 1F Ceramic Cap at VOUT Pin needed for stable regulation
10 9 8 7 6
1 2 3 4 5
VBATT LBI LBON RLIM SHDN
VOUT
SP6648 LX
PGND GND FB
C4 1F
R1 16.2k
C2 10F
D2 1W LED 350mA
R5 10K
D1 1N4148
VREF = 0.61V Rb 1.8
RLIM 1.87K
(R5 optional)
IOUT=0.61V/Rb
SP6648LEDEB Evaluation Board Schematic
100 95 90
85 80 75 70 65 60 1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
As shown in following scope photos, if the SP6648 is powered up before the LumiLED is plugged in, the circuit will bring the Feedback pin to 0V and the SP6648 has a feature to set the output voltage to be 3.3V. Once the LumiLED is plugged in, the Feedback pin will go up to 1.25V and begin to regulate. The output voltage will go from 3.3V to 3.68V (=VF+0.61V), where VF is the forward voltage of the LumiLED. When the LumiLED is open, the Feedback pin voltage will go to 0V and the output voltage will go to 3.3V which will protect the part.
Efficiency (%)
Battery Voltage (V)
SP6648LEDEB Efficiency Curve
Date: 7/19/04
SP6648 Ultra-low Quiescent Current, High Efficiency Boost Regulator
(c) Copyright 2004 Sipex Corporation
12
APPLICATIONS INFORMATION
VOUT
VOUT
VREF
VREF
Plug in the LumiLED
Unplug the LumiLED
Brightness Control
One approach to control LED brightness is to apply a PWM signal to the SHDN input of the SP6648. In this case, the output current will be equal to the product of 350mA and the average duty cycle at the SHDN pin. An optional 10K potentiometer (R5) may also be used for dimming the LED current by varying the potentiometer between low brightness and full brightness. PINOUTS
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
VBATT 1 LBI 2 LBON 3 RLIM 4 SHDN 5
10 VOUT
SP6648
10 Pin MSOP
9 LX 8 PGNDV 7 GND 6 FB
Date: 7/19/04
SP6648 Ultra-low Quiescent Current, High Efficiency Boost Regulator
(c) Copyright 2004 Sipex Corporation
13
PACKAGE: 10 PIN MSOP
(ALL DIMENSIONS IN MILLIMETERS)
D e1
O1
E/2
R1 R Gauge Plane L2 Seating Plane
1 2
E
E1
O1
L L1
O
e Pin #1 indentifier must be indicated within this shaded area (D/2 * E1/2)
Dimensions in (mm)
10-PIN MSOP JEDEC MO-187 (BA) Variation MIN NOM MAX 0 0.75 0.17 0.08 0.85 3.00 BSC 4.90 BSC 3.00 BSC 0.50 BSC 2.00 BSC 0.4 0.07 0.07 0 0 0.60 0.95 0.25 10 0.80 8 15 1.1 0.15 0.95 0.27 0.23
A A1 A2 b c D E E1 e e1 L L1 L2 N R R1 O O1
(b)
WITH PLATING
c
BASE METAL
D A2 b A1 A
1
Date: 7/19/04
SP6648 Ultra-low Quiescent Current, High Efficiency Boost Regulator
(c) Copyright 2004 Sipex Corporation
14
PACKAGE: 10 PIN DFN
D D/2 A3
E/2
E
Top View
A1 A
Side View
D2 1 2
10 Pin DFN
E2
(JEDEC MO-229, VEED-5 VARIATION)
DIMENSIONS in (mm)
K L e b
Bottom View
SYMBOL A A1 A3 b D D2 e E E2 K L
MIN NOM MAX
0.80 0.90 1.00
0
0.02 0.05
0.20 REF
0.18 0.25 0.30 3.00 BSC 2.20 2.70 0.50 PITCH 3.00 BSC 1.40 1.75 0.20 0.30 0.40 0.50
10 Pin DFN
Date: 7/19/04 SP6648 Ultra-low Quiescent Current, High Efficiency Boost Regulator (c) Copyright 2004 Sipex Corporation
15
ORDERING INFORMATION
Part Number Top Mark Operating Temperature Range Package Type
SP6648EU ................................ SP6648EU..................-40C to +85C ...................................... 10 Pin MSOP SP6648EU/TR .......................... SP6648EU..................-40C to +85C ..................................... 10 Pin MSOP SP6648ER ............................... SP6648ERYWW..........-40C to +85C ........................................ 10 Pin DFN SP6648ER/TR ......................... SP6648ERYWW..........-40C to +85C ....................................... 10 Pin DFN Available in lead free packaging. To order add "-L" suffix to part number. Example: SP6648EU/TR = standard; SP6648EU-L/TR = lead free /TR = Tape and Reel Pack quantity is 2,500 for MSOP and 3,000 for DFN.
Corporation
ANALOG EXCELLENCE
Sipex Corporation Headquarters and Sales Office 233 South Hillview Drive Milpitas, CA 95035 TEL: (408) 934-7500 FAX: (408) 935-7600
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: 7/19/04
SP6648 Ultra-low Quiescent Current, High Efficiency Boost Regulator
(c) Copyright 2004 Sipex Corporation
16

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