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SP6648LEDEB

器件型号:SP6648LEDEB
厂商名称:SIPEX
厂商官网:
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Evaluation Board Manual

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SP6648LEDEB器件文档内容

                                               SP6648LED
                                     Evaluation Board Manual

   Easy evaluation for SP6648
   performance of driving 1W
   LumiLED.
   Plug & Light ON
   Self Protection
   Programmable Inductor Peak
   Current
   High Efficiency: up to 94%
   �SOIC Package & SMT
   components for small, low profile
   Power Supply

DESCRIPTION AND BOARD SCHEMATIC

The SP6648LED Evaluation Board is designed to help the user evaluate the performance of
the SP6648 for use as a dual cell input to drive a 1W LumiLED. The evaluation board is a
completely assembled and tested surface mount board which provides easy probe access
points to all SP6648 inputs and outputs so that the user can quickly connect and measure
electrical characteristics and waveforms.

                                                                                                                             16K
USING THE EVALUATION BOARD

1) Powering Up the SP6648LED Circuit

The SP6648LED Evaluation Board can be powered from inputs from a +1.8V to +3.2V power
supply or from 2 alkaline cells. Connect with short leads directly to the "VIN" and "GND" posts.
Plug the 1W LumiLED between the "VOUT" and "REF" posts. Unlike other boost regulators, the
part has self-protection feature. It will not be damaged when the output is open as long as there
is a low resistance from FB to GND. As shown in Figures 1 and 2, if the board 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) accordingly (as shown in Fig. 1), 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 (as shown in Fig 2).

                                VOUT  VOUT

                                VREF  VREF

         Fig 1. Plug in the LumiLED   Fig. 2. Unplug the LumiLED

2) Using the J1 Jumper: Enabling the SP6648 Output and using the Shutdown Mode

The SP6648 output will be enabled if the J1 Jumper is in the top or pin 1 to 2 position. If J1 is in
the pin 2 to 3 position, the Shutdown pin is brought to GND, which puts the SP6648 in the low
quiescent Shutdown Mode.

3) Selecting the Bias Resistor

In the white LEDs application, the SP6648 is generally programmed as a current source. The

bias resistor 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 Ohm as shown in the schematic.

4) 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 R6 & R7 to control the
output voltage. To set Vout in the voltage mode, use the equation:

R6  =    Vout  -  1  �  R  7
         0.61      
5) 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 = 1400/RLIM

The SP6648 datasheet specifications for RLIM give a range of 1.87K to 4K ohms. Using the IPEAK
equation above gives an IPEAK range of 350 to 750mA.
The saturation current specified for the inductor needs to be greater then 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 = 750mA 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.

6) Using the LBON - Low Battery Output Function

The SP6648 will regulate the output current until the input battery is completely discharged. To
provide an early low battery warning, the Low Battery Output function of the SP6648 switching
regulator can be used. LBON is programmed externally by the R1 and R2 resistor divider
connected between VIN, the LBI input pin and GND. When the LBI comparator falling threshold
of 0.61V is reached, D1 switches on, indicating low battery condition. Low battery detect trip
point can be calculated by the following formula:

VLOWBAT  =  0.61  R1 + R2
                     R2

The SP6648 evaluation board R1 & R2 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.

7) 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 additional 10K potentiometer (R5) may also be used for dimming
LED. LED current is varied by the potentiometer between almost zero and full 350mA.

POWER SUPPLY DATA
For the standard evaluation board, The efficiency curve is shown in the figure below.

                                           100
                                            95

                                           90

                           Efficiency (%)  85
                                           80
                                           75

                                           70

                                           65

                                           60

                                                1.8  2.0  2.2  2.4  2.6             2.8  3.0  3.2

                                                               Battery Voltage (V)

                  Fig.3 Efficiency curve of the SP6648LED evaluation board
EVALUATION BOARD LAYOUT
                          FIGURE 1: SP6648LEDEB COMPONENT PLACEMENT
                             FIGURE 2: SP6648LEDEB PC LAYOUT TOP SIDE
                          FIGURE 3: SP6648LEDEB PC LAYOUT BOTTOM SIDE
TABLE1: SP6648LEDEB LIST OF MATERIALS

              SP6648LED Evaluation Board List of Materials

Ref. Des.  Qty. Manufacturer  Part Number     Layout Size   Component                  Vendor

      U1                                      LxWxH
   C1,C3
           1 Sipex Corp.      146-6510-00     1"x2.14"      SP6648LED Eval PC Board    Future 888-589-3662
      C2
      L1   1 Sipex Corp.      SP6648EU        MSOP-10 10 PIN High Efficiency Boost Regulato Future 888-589-3662
      R1
      R2   2 TDK Corp TDKC3216X5R0J106K       1206          10uF/6.3V/X5R/10% Ceramic  Future 888-589-3662
      R3
      R4   1 TDK Corp TDKC1608X5R0J105K       603           1uF/6.3V/X5R/10% Ceramic   Future 888-589-3662
      R5
      R6   1 Sumida           CD43-100        4x4.5x3.2mm 10uH, 1.04A, 0.18 Ohm, SM inductor Future 888-589-3662
      R7
    Rlim   1  Rohm            MCR03EZPFX1003  603           100K 1/16W 1% 0603 SM      Future 888-589-3662
      Rb
      D1   1  Rohm            MCR03EZPFX4322  603           43.2K 1/16W 1% 0603 SM     Future 888-589-3662
      D2
      TP   1  Rohm            MCR03EZPFX1501  603           Open                       Future 888-589-3662
      J1
           1  Rohm            MCR03EZPFX1622  603           16.2K 1/16W 1% 0603 SM     Future 888-589-3662

           1  Rohm            MVR32HXBRN103 3x3.6x1.3mm 0 Ohm between pin 1 and pin 3 Future 888-589-3662

           1  Rohm                                          Open                       Future 888-589-3662

           1  Rohm                                          Open                       Future 888-589-3662

           1  Rohm            MCR03EZPFX1871  603           1.87K 1/16W 1% 0603 SM     Future 888-589-3662

           1  Rohm            MCR25JZHJ1R8    1210          1.8 Ohm 1/4W 5% 1210 SM    Future 888-589-3662

           1 Stanley          BR1101W-TR      3x1.5x1.5mm   Open                       Future 888-589-3662

           1 Diode Inc.       1N4148W-7       SOD-123       75V 150mA SM Diode         Future 888-589-3662

           7 Mill-Max 0300-115-01-4701100 .042 Dia          Test Point Female Pin      Future 888-589-3662

           1  Sullins         PTC36SAAN       .23x.12       2-Pin Header               Future 888-589-3662

                              ORDERING INFORMATION

Model                         Temperature Range                                      Package Type

SP6648LEDEB............................. -40�C to +85�C...................SP6648LED Evaluation Board
SP6648EU.....................................-40�C to +85�C...................................... 10-pin �SOIC
This datasheet has been downloaded from:
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