CDB5376 Cirrus Logic Inc, CDB5376 Datasheet - Page 16

• Manufacturer Part Number: CDB5376
• Description: EVALUATION BOARD FOR CS5376
• Manufacturer: Cirrus Logic Inc

Specifications of CDB5376

• Main Purpose: Seismic Evaluation System
• Embedded: Yes, MCU, 8-Bit
• Utilized Ic / Part: CS3301A, CS3302A, CS4373A, CS5372A, CS5376A
• Primary Attributes: Quad Digital Filter
• Secondary Attributes: Graphical User Interface, SPI™ & USB Interfaces
• Processor To Be Evaluated: CS330x, CS4373A, CS537x
• Interface Type: USB
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Contains lead / RoHS non-compliant
• Other names: 598-1778

4. ANALOG SIGNALS
The CS5371A and CS5372A modulators have
differential analog inputs which are separated
into rough and fine charge differential pairs
(INR±, INF±) to maximize sampling accuracy.
Both sets of modulator inputs require a simple
differential anti-alias RC filter to ensure high-
frequency signals do not alias into the mea-
surement bandwidth.
4.1 INR±, INF± Modulator Inputs
The modulator analog inputs are separated
into differential rough and fine signals (INR±,
INF±). The positive half of the differential input
signal is connected to INR+ and INF+, while
the negative half is attached to INF- and INR-.
The INR± pins are switched-capacitor ‘rough
charge’ inputs that pre-charge the internal an-
alog sampling capacitor before it is connected
to the INF± fine input pins.
16
VA+
VA+
VA-
VA-
VA+
VA+
VA-
VA-
AMPLIFIER
AMPLIFIER
CS3301A
CS3302A
CS3301A
CS3302A
VA+
VA-
OUTR+
OUTF+
OUTF-
OUTR-
OUTR+
OUTF+
OUTF-
OUTR-
VREF
2.5 V
680
680
680
680
680
680
680
680
10 Ω
100μF
20nF
20nF
C0G
C0G
Figure 11. Analog Signals
VA+
VA-
0.01μF
20nF
C0G
20nF
C0G
INR+
INF+
INF-
INR-
VREF+
VREF-
INR-
INF-
INF+
INR+
0.1μF
0.1μF
4.2 Input Impedance
The modulator inputs have a dynamic
switched-capacitor architecture and so have a
rough charge input impedance that is inversely
proportional to the input master clock frequen-
cy and the input capacitor size, [1 / (f x C)].
Internal to the modulator, the rough inputs
(INR±) pre-charge the sampling capacitor
used by the fine inputs (INF±), therefore the in-
put current to the fine inputs is typically very
low and the effective input impedance is or-
ders of magnitude above the impedance of the
rough inputs.
VA+
ΔΣ Modulator
VA-
•
•
•
CS5372A
MCLK = 2.048 MHz
INR± Internal Input Capacitor = 20 pF
Impedance = [1 / (2.048 MHz * 20 pF)] = 24 kΩ.
GND
VD
MDATA2
MFLAG2
MDATA1
MFLAG1
MSYNC
PWDN2
PWDN1
0.01μF
MCLK
OFST
VD
CS5371A CS5372A
MDATA1
MFLAG1
GPIO
MCLK
MSYNC
GPIO
MDATA2
MFLAG2
GPIO
Digital Filter
CS5376A
VDD2
GND
VD
DS748F3