MAX1249AMJE Maxim Integrated, MAX1249AMJE Datasheet - Page 19

• Manufacturer Part Number: MAX1249AMJE
• Description: Analog to Digital Converters - ADC
• Manufacturer: Maxim Integrated

Specifications of MAX1249AMJE

• Number Of Channels: 4/2
• Architecture: SAR
• Conversion Rate: 133 KSPs
• Resolution: 10 bit
• Input Type: Single-Ended/Differential
• Snr: 64 dB
• Interface Type: 4-Wire (SPI, Microwire, QSPI, TMS320)
• Operating Supply Voltage: 2.7 V to 5.25 V
• Maximum Operating Temperature: + 125 C
• Package / Case: CDIP N
• Maximum Power Dissipation: 667 mW
• Minimum Operating Temperature: - 55 C
• Number Of Converters: 1
• Voltage Reference: External

Figure 17. Bipolar Transfer Function, Zero Scale (ZS) = COM,
Full Scale (FS) = VREF / 2 + COM
Table 7. Full Scale and Zero Scale
For best performance, use printed circuit boards.
Wire-wrap boards are not recommended. Board layout
should ensure that digital and analog signal lines are
separated from each other. Do not run analog and digi-
tal (especially clock) lines parallel to one another, or
digital lines underneath the ADC package.
Figure 18 shows the recommended system ground
connections. Establish a single-point analog ground
(star ground point) at AGND, separate from the logic
ground. Connect all other analog grounds and DGND
to the star ground. No other digital system ground
should be connected to this ground. For lowest noise
operation, the ground return to the star ground’s power
supply should be low impedance and as short as pos-
sible.
011 . . . 111
011 . . . 110
000 . . . 010
000 . . . 001
000 . . . 000
111 . . . 111
111 . . . 110
111 . . . 101
100 . . . 001
100 . . . 000
OUTPUT CODE
VREF + COM
Full Scale
*COM
Layout, Grounding, and Bypassing
-FS =
1LSB =
- FS
FS = VREF
ZS = COM
VREF / 2
-VREF
______________________________________________________________________________________
2
2
VREF
1024
+2.7V to +5.25V, Low-Power, 4-Channel,
UNIPOLAR MODE
+ COM
+ COM
INPUT VOLTAGE (LSB)
COM*
Zero Scale
COM
Serial 10-Bit ADCs in QSOP-16
+FS - 1LSB
High-frequency noise in the V
affect the ADC’s high-speed comparator. Bypass the
supply to the star ground with 0.1µF and 1µF capaci-
tors close to pin 1 of the MAX1248/MAX1249. Minimize
capacitor lead lengths for best supply-noise rejection.
If the +3V power supply is very noisy, a 10Ω resistor
can be connected as a lowpass filter (Figure 18).
The MAX1248/MAX1249 can interface with QSPI using
the circuit in Figure 19 (f
CPHA = 0). This QSPI circuit can be programmed to do a
conversion on each of the four channels. The result is
stored in memory without taxing the CPU, since QSPI
incorporates its own micro-sequencer.
The MAX1248/MAX1249 are QSPI compatible up to their
maximum external clock frequency of 2MHz.
Figure 18. Power-Supply Grounding Connection
R* = 10
High-Speed Digital Interfacing with QSPI
Full Scale
VREF / 2
Positive
+ COM
* OPTIONAL
V
+3V
DD
AGND
MAX1248
MAX1249
BIPOLAR MODE
Scale
COM
Zero
SCLK
SUPPLIES
COM
DD
= 2.0MHz, CPOL = 0,
DGND
power supply may
Full Scale
-VREF / 2
Negative
+ COM
+3V
+3V
CIRCUITRY
DIGITAL
DGND
GND
19