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BH2715FV Datasheet(PDF) 9 Page - Rohm
BH2715FV Datasheet(HTML) 9 Page - Rohm
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© 2016 ROHM Co., Ltd. All rights reserved.
Application Circuit Example
1. Bypass Capacitor
Because the voltages of AVDD and AGND are used as the reference voltages for the A/D conversion, the deviation
of the supply voltages directly affects A/D conversion accuracy. Please ensure to insert a low ESR bypass
condenser (equal to or more than 0.1µF) between AVDD and AGND.
DVDD and DGND are the power supply and ground lines of the digital block. Please ensure to insert bypass
condenser (equal to or more than 0.1µF) between DVDD and DGND.
2. Pull-down Resistor on SDOUT
SDOUT is a digital output terminal with a 3-state output buffer. When CSB=H, the SDOUT output is Hi-Z and the
SDOUT line is floating. Please insert a pull-down resistor or a pull-up resistor as needed. A low resistance
pull-up/pull-down resistor is not necessary, because SDOUT has a CMOS output buffer. Please insert a high
resistance resistor. The resistance should be decided so that a circuit (microprocessor, etc.) which receives SDATA
output doesn't malfunction.
3. External Circuit of Analog Input Terminals IN0 through IN7
Voltages of the terminals IN0 through IN7 are used for A/D conversions. Capacitors between the analog input
terminals and ground should be placed as close to the analog input terminals as possible. A low ESR capacitor
which has equal to or higher than 47pF is recommended. A capacitor C
should be connected to a ground with
low noise like AGND. When conversion results are not stable, please insert a resistor R
between Vconv, which is
an A/D conversion input voltage, and INx. Conversion results are improved by a first-order low pass filter
composed of C
. Please decide the values of C
in consideration of the slew-rate or the
frequency characteristic of Vconv. The lower cut-off frequency of the low pass filter makes the higher noise
rejection rate from Vconv and the better A/D conversion characteristics of the BH2715FV as long as the low pass
filter rejects a necessary signal frequency in Vconv.
4. Crosstalk between Analog Input Terminals and Noise Sources
Design a wire layout on a printed circuit board which doesn't cause crosstalk between the A/D conversion input
signal lines IN0 through IN7 and other signal lines of possible noise sources due to capacitive coupling.
Particularly, it should be avoided to route a input signal line in parallel with a noise source line. If it is unavoidable
that an A/D conversion input line intersects with a noise source line, it is desired to make it orthogonal and also to
take a measure to prevent crosstalk such as inserting a ground shield between layers of the printed circuit board.
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