SP6641A/6641B Evaluation Board Schematics
Easy Evaluation for the
SP6641A/6641B Single or
Dual Cell Alkaline to 3.3V or
5V Output
SP6641B provides up to
500mA output current with
less than 50mVpp ripple
High Efficiency: up to 87%
SOT23-5 Package & SMT
components for small, low
SP6641A/6641B
Low Noise Evaluation Board
L1
22uH
Ceramic
0.9V to 3.3V
Ceramic
J1
1
2
3
SHDN
SP6641A 1 OR 2 CELL BOOST
C3
1uF Cer.
U1 SP6641A
1
2
4
5
3
LX
GND
SHDN
VBATT
VOUT
C1
22uF
VOUT
VBATT
C2
22uF
D1
SCHOTTKY DIODE
L2
SM Bead
U1 SP6641B
1
2
4
5
3
LX
GND
SHDN
VBATT
VOUT
C1
100uF
C2
330uF
VFILTER
C3
1uF Cer.
L1
10uH
40mohm
SP6641B 2 CELL BOOST
VBATT
J1
1
2
3
D1
SCHOTTKY DIODE
C4
10uF Ceramic
80mohm
VOUT
1.8V to 3.3V
SHDN
USING THE EVALUATION BOARD
1) Powering Up the SP6641A/6641B Circuit
The SP6641A/6641B Evaluation Board can be powered from inputs from a +0.9V to +3.3V from
1 or 2 alkaline cells or a power supply. 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
"GND" post.
2) Using the J1 Jumper: Enabling the SP6641A/6641B Output and using the Shutdown
Mode
The SP6641A/6641B output will be enabled if the J1 Jumper is in the upper 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
SP6641A/6641B in the low quiescent Shutdown Mode.
3) Selecting the Inductor
In selecting an inductor, the saturation current specified for the inductor needs to be greater
then the SP6641A/6641B peak current to avoid saturating the inductor, which would result in a
loss in efficiency and could damage the inductor. The SP6641A evaluation board uses a
Sumida CDRH5D28 22uH inductor with an Isat value of 0.9A and a DCR of 0.095ohms, which
easily handles the Ipeak of 0.33A of the SP6641A and will deliver high efficiencies. The
SP6641B evaluation board uses a Sumida CDRH5D28 10uH inductor with an Isat value of 1.3A
and a DCR of 0.065ohms, which easily handles the Ipeak of 1.0A of the SP6641B and will
deliver high efficiencies. Other inductors could be selected provided their Isat is greater than the
Ipeak of the SP6641A/6641B.
4) Selecting the Capacitors and Filter Components
For the SP6641A, 22uF ceramic capacitors are used, which work well due to their inherently low
ESR, which will help produce low peak to peak output ripple, and reduce high frequency spikes
as well due to their low impedance. To obtain low peak to peak ripple for the SP6641B, the
output capacitor needs to have ESR as low as 35 to 40 mohms and have a value of at least
100uF, for which the 330uF Sanyo POSCAP was chosen for its 40mohms max. ESR. Other
ultra low ESR capacitors such the radial lead 100uF Sanyo OSCON or one of the new SM low
ESR Polymer capacitors like the 100uF Panasonic UD series could be used. This low ripple is
obtained with no output spikes through the use of a LC filter consisting of small 0805 SM bead
core L2 and 10uF ceramic capacitor C3.
POWER SUPPLY DATA
Power supply data is provided for the "B" version of the SP6641B, which has a peak inductor
current limit of 1A, with the 3.3V output option. Figure 1 shows the switching signals still present
as 1.0V spikes on the 330uF capacitor C2. Note that no output spikes are seen in figures 2 and
3 through the use of a small LC filter after the 330uF capacitor. The SP6641B's low output ripple
of 45 to 50mVpp is shown for a typical input of 2.0V to 3.0V and an output load of 300mA.
Figure 1. SP6641B Switching Signals on 330uF: Vin = 2.0V, Iout = 300mA, Spikes = 1.0Vpp
Figure 2. SP6641B Output Ripple: Vin = 2.0V, Iout = 300mA, Vout ripple = 42mVpp,
51kHz
Figure 3. SP6641B Output Ripple: Vin = 3.0V, Iout = 500mA, Vout ripple = 54mVpp,
50kHz
TABLE1: SP6641A BILL OF MATERIALS
TABLE2: SP6641B BILL OF MATERIALS
ORDERING INFORMATION
Model
Temperature Range
Package Type
SP6641AKEB-3.3................................-40
C to +85
C...............SP6641A 3.3V Evaluation Board
SP6641AEK-3.3.....................................-40
C to +85
C......................................5-pin SOT23
SP6641AKEB-5.0.................................. -40
C to +85
C...........SP6641A 5.0V Evaluation Board
SP6641AEK-5.0.....................................-40
C to +85
C......................................5-pin SOT23
SP6641BKEB-3.3.................................. -40
C to +85
C...........SP6641B 3.3V Evaluation Board
SP6641BEK-3.3.....................................-40
C to +85
C......................................5-pin SOT23
SP6641BKEB-5.0.................................. -40
C to +85
C...........SP6641B 5.0V Evaluation Board
SP6641BEK-5.0.....................................-40
C to +85
C......................................5-pin SOT23
Ref. Des. Qty.
Manufacturer
Part Number
Layout Size
Component
Vendor
LxWxH
1
Sipex Corp.
146-6447-03
1"x1.5"
SP6641 Eval PC Board
Sipex 978-667-8700
U1
1
Sipex Corp.
SP6641BEK-3.3 or 5.0
SOT23-5
5-pin SOT23 Step-Up DC/DC Conv
Sipex
C1
1
Sanyo Video
10TPA100M
7343
POSCAP 10V 100uF SM 0.080ohm Max. ESR
Sanyo 978-922-6573
C2
1
Sanyo Video
6TPB330M
7343
POSCAP 6.3V 330uF SM 0.040ohm Max. ESR Sanyo 978-922-6573
C3
1
TDK Corp
C2012X5R1A105M
805
Ceramic 10V 1uF SM 0.02ohm ESR
TDK 847-803-6100
C4
1
TDK Corp
C3216X5R0J106M
1206
Ceramic 6.3V 10uF SM 0.005ohm ESR
TDK 847-803-6100
L1
1
Sumida
CDRH5D28-100
5.7x5.5x3
10uH, 1.3A, 0.065ohm, SM Inductor
Sumida 847-956-0666
L2
1
Panasonic
EXC-ML20A390U
805
SM Bead Core 100MHz
800-Digi-Key
D1
1
Zetex
ZCHS2000
SOT23-6
Schottky diode 2A, 0.42V
Zetex 631-360-2222
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
Ref. Des. Qty.
Manufacturer
Part Number
Layout Size
Component
Vendor
LxWxH
1
Sipex Corp.
146-6447-03
1"x1.5"
SP6641 Eval PC Board
Sipex 978-667-8700
U1
1
Sipex Corp.
SP6641AEK-3.3 or 5.0
SOT23-5
5-pin SOT23 Step-Up DC/DC Conv
Sipex
C1,C2
2
TDK Corp
C3225X5R0J226K
1210
Ceramic 6.3V 22uF SM 0.005ohm ESR
TDK 847-803-6100
C3
1
TDK Corp
C2012X5R1A105K
805
Ceramic 10V 1uF SM 0.02ohm ESR
TDK 847-803-6100
L1
1
Sumida
CDRH5D28-220
5.7x5.5x3mm
22uH, 0.90A, 0.095ohm, SM Inductor
Sumida 847-956-0666
D1
1
STMicroelectronics
STPS0520Z
SOD-123
Schottky diode 0.5A, 0.385V
STMicro 847-585-3023
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
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