DESCRIPTION
The SP6648 Evaluation Board is designed to help the user evaluate the performance of the
SP6648 for use as a single or dual cell input to +3.3V output DC-DC Converter. The output of
the SP6648 is preset to +3.3V or can be adjusted from +2V to +5.5V by manipulating two
external resistors. 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.
SP6648 EVALUATION BOARD SCHEMATIC
RLIM
1.87K
LBON
VBATT
+ C2
47uF
3.3Vout
L1 10uH
C3
47pF
SP6648
1
2
4
5
6
7
8
3
9
10
VBATT
LBI
RLIM
SHDN
FB
GND
PGND
LBON
LX
VOUT
R2
124K
LBI
SHDN
R1
205K
C4
1uF
+
C1
47uF
Easy Evaluation for the
SP6648 Single or Dual Cell
Alkaline to 2V to 5V Output
Provides 300mA output at
3.3V output for 2.0V Input
High Efficiency: 94%
SOIC Package & SMT
components for small, low
profile Power Supply
SP6648
Evaluation Board Manual
USING THE EVALUATION BOARD
1) Powering Up the SP6648 Circuit
The SP6648 Evaluation Board can be powered from inputs from a +0.95V to +3.3V from 1 or 2
alkaline cells. Connect with short leads directly to the "Vbatt" and "Gnd" posts. Monitor the
Output Voltage and connect the Load between the "Vout" post and the 2
nd
"GND" post.
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) Using the Rlim Function
The peak inductor current, I
PEAK
, is programmed externally by the
RLIM resistor connected
between the RLIM pin and GND. The peak inductor current is defined by:
I
PEAK
= 1400/R
LIM
The SP6648 datasheet specifications for RLIM give a range of 1750 to 4000 ohms. Using the
IPEAK equation above gives an IPEAK range of
I
PEAK
range = 350 to 800mA.
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.
4) Using the LBON - Low Battery Output Function
The Low Battery Output function, 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 0.625V is reached, the LBON output goes low as determined by
the relationship:
LBON falling = Vbatt*R4/(R3 +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.
FIGURE 1: SP6648UEB COMPONENT PLACEMENT
FIGURE 2: SP6648UEB PC LAYOUT TOP SIDE
FIGURE 3: SP6648UEB PC LAYOUT BOTTOM SIDE
TABLE1: SP6648EB LIST OF MATERIALS
ORDERING INFORMATION
Model
Temperature Range
Package Type
SP6648UEB.................................. -40
C to +85
C...................SP6648 Evaluation Board
SP6648EU.....................................-40
C to +85
C......................................10-pin
SOIC
Ref. Des. Qty. Manufacturer
Part Number
Layout
Component
Vendor
Size
1
Sipex Corp.
146-6479-00
1"x1.5"
SP6648UEB Eval PC Board
Sipex 978-667-7800
U1
1
Sipex Corp.
SP6648EU
uSO-8
10-pin uSOIC Step-Up DC/DC Conv
Sipex
C1,2
2
Kemet
T494C476K010AS
"D" size
47uF 10V SM 0.3ohm ESR
Kemet 847-517-1030
C1,2
2
Kemet
T494V476K010AS
"V" size
47uF 10V low profile SM 0.3ohm ESR
Kemet 847-517-1030
C3
1
TDK Corp
C1608SL1H470K
0603
Ceramic 16V 47pF SM
TDK 847-803-6100
C4
1
TDK Corp
C1608X5R1A105M
0603
Ceramic 10V 1uF SM 0.02ohm ESR
TDK 847-803-6100
L1
1
Sumida
CDRH5D28-100
6.7x6.5x3.0mm
10uH, 1.3A, 0.065ohm, SM Inductor
Sumida 847-956-0666
L1
1
TDK Corp
RLF5018-100MR94
5.6x5.2x2.0mm 10uH, 0.94A, 0.067ohm, SM Inductor
TDK 847-803-6100
R1
1
Panasonic
ERJ-3EKF2053
0603
205K ohm 1/8W 1% 0603 SM
Digi-Key 800-344-4539
R2
1
Panasonic
ERJ-3EKF2493
0603
124K ohm 1/8W 1% 0603 SM
800-Digi-Key
R3
1
Panasonic
ERJ-3EKF5493
0603
549K ohm 1/8W 1% 0603 SM
800-Digi-Key
R4
1
Panasonic
ERJ-3EKF2493
0603
249K ohm 1/8W 1% 0603 SM
800-Digi-Key
R5
1
Panasonic
ERJ-3GEYJ105
0603
1M ohm 1/8W 5% 0603 SM
800-Digi-Key
RLIM
1
Panasonic
ERJ-3EKF1871
0603
1.87K ohm 1/8W 1% 0603 SM
800-Digi-Key
TP
5
Mill-Max
0300-115-01-4727100
.042 Dia
Test Point Female Pin
800-Digi-Key
J1
1
Sullins
PTC36SAAN
.23x.12
3-Pin Header
800-Digi-Key
1
Sullins
STC02SYAN
.2x.1
Shunt
800-Digi-Key
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