AS1542-BTSU ams, AS1542-BTSU Datasheet - Page 13

• Manufacturer Part Number: AS1542-BTSU
• Description: Analog to Digital Converters - ADC
• Manufacturer: ams

Specifications of AS1542-BTSU

• Rohs: yes
• Number Of Channels: 16/8
• Architecture: SAR
• Conversion Rate: 1 MSPs
• Resolution: 12 bit
• Input Type: Single-Ended/Differential
• Snr: 71 dB
• Interface Type: QSPI, SPI
• Operating Supply Voltage: 2.7 V to 5.25 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Package / Case: TSSOP-28
• Maximum Power Dissipation: 18.4 mW
• Minimum Operating Temperature: - 40 C
• Number Of Converters: 1

AS1542
Data Sheet - D e t a i l e d D e s c r i p t i o n
Figure 22. Data Conversion
Analog Input
Figure 23
analog inputs. Care should be taken to ensure that the analog input signal never exceeds the supply rails by more than
300mV. This will cause these diodes to become forward biased and start conducting current into the substrate. 10mA
is the maximum current these diodes can conduct without causing irreversible damage to the AS1542.
Figure 23. Equivalent Analog Input Circuit
Capacitor C1 in
lumped component made up of the on-resistance of a switch (track/hold switch) and also includes the on-resistance of
the input multiplexer. The total resistance is typically about 400Ω. Capacitor C2 is the ADC sampling capacitor and typ-
ically has a capacitance of 20pF.
Track/Hold
The Track/Hold stage enters hold mode on the falling edge of CSN. For AC applications, removing high frequency
components from the analog input signal is recommended by use of an R/C low-pass filter on the relevant analog input
pin. In applications where harmonic distortion and signal-to-noise ratio are critical, the analog input should be driven
from a low impedance source. Large source impedances will significantly affect the ac performance of the ADC. This
may necessitate the use of an input buffer amplifier. The choice of the op-amp will be a function of the particular appli-
cation.
When no amplifier is used to drive the analog input, the source impedance should be limited to low values. The maxi-
mum source impedance will depend on the amount of total harmonic distortion that can be tolerated. The THD will
increase as the source impedance increases, and performance will degrade
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C
SWITCH
shows an equivalent circuit of one analog input. The two diodes, D1 and D2, provide ESD protection for the
Analog Input
CH15
AGND
includes all parasitics
Multiplexer
CH0
CH1
CH2
CH3
CH4
CH5
Figure 23
is typically about 4pF and can primarily be attributed to pin capacitance. The resistor R1 is a
V
INX
AIN+
AIN-
C
C
C1
4pF
SWITCH
SWITCH
11pF
11pF
Input
Switch
Input
Switch
REFIN
D1
D2
S&H and capacitive DAC
Revision 1.00
C
C
13pF
13pF
–
–
HOLD
HOLD
+
+
Open for Conversion;
Closed for Track
Sample
Switch
R
IN
R1
20pF
C2
AGND
(see Figure 13 on page
+
–
Comparator
10).
Control
Logic
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