ADS-942 MURATA-PS [Murata Power Solutions Inc.], ADS-942 Datasheet - Page 3

• Manufacturer Part Number: ADS-942
• Description: 14-Bit, 2MHz Sampling A/D Converters
• Manufacturer: MURATA-PS [Murata Power Solutions Inc.]

TECHNICAL NOTES
1. Rated performance requires using good high-frequency
2. Bypass the analog and digital supplies and the +10V REF.
3. CODING SELECT(pin 8) is compatible with CMOS/TTL
4. To enable the three-state outputs, connect ENABLE (pin 9)
CALIBRATION PROCEDURE
1. Connect the converter per Figure 3 and Table 1 for the
2. Zero Adjustments
INPUT RANGE
circuit board layout techniques. Connect the digital and
analog grounds to one point, the analog ground plane
beneath the converter. Due to the inductance and resis-
tance of the power supply return paths, return the analog
and digital ground separately to the power supplies.
SIGNAL GROUND (pin 4) is not internally connected to
ANALOG GROUND (pins 6, 15).
OUT (pin 1) to ground with a 4.7µF, 25V tantalum electro-
lytic capacitor in parallel with a 0.1µF ceramic capacitor.
logic levels for those users desiring logic control of this
function. There is an internal pull-up resistor on this pin;
connect to +5V or leave open for logic 1. See the Calibra-
tion Procedure for selecting an output coding.
to a logic "0" (low). To disable, connect pin 9 to a logic "1"
(high).
appropriate input voltage range. Apply a pulse of 35
nanoseconds minimum to START CONVERT (pin 32) at a
rate of 200kHz. This rate is chosen to reduce flicker if LED's
are used on the outputs for calibration purposes.
Apply a precision voltage reference source between
ANALOG INPUT (pin 3) and SIGNAL GROUND (pin 4),
then adjust the reference source output per Table 2.
®
0 +10V
±5V
Table 1. Input Connections
INTERNAL S/H
CONVERT
INPUT PIN
OUTPUT
START
Pin 3
Pin 3
DATA
®
EOC
Note: Scale is approximately 25ns per division.
TIE TOGETHER
DATA N-1 VALID
Pins 2 and 4
Pins 1 and 2
300ns min.
N
Figure 2. ADS-942 Timing Diagram
10ns typ.
15ns max.
35ns min., 50ns typ., 60 ns max
300ns typ., 325ns max.
350ns min.
Conversion Time
Hold
35ns max..
3
3. Full-Scale Adjustment
4. To confirm proper operation of the device, vary the precision
INVALID DATA
For unipolar, adjust the zero trimpot so that the output code
flickers equally between 00 0000 0000 0000 and 00 0000
0000 0001 with CODING SELECT (pin 8) tied low (straight
binary) or between 11 1111 1111 1111 and 11 1111 1111
1110 with pin 8 tied high (complementary binary).
For bipolar operation, adjust the trimpot until the code
flickers equally between 10 0000 0000 0000 and 10 0000
0000 0001 with pin 8 tied low (offset binary) or between 01
1111 1111 1111 and 01 1111 1111 1110 with pin 8 tied high
(complementary offset binary).
Two's complement coding requires using BIT 1 OUT (MSB)
(pin 31). With pin 8 tied low, adjust the trimpot until the code
flickers between 00 0000 0000 0000 and 00 0000 0000
0001.
Set the output of the voltage reference used in step 2 to the
value shown in Table 2.
Adjust the gain trimpot until the output code flickers equally
between 11 1111 1111 1110 and 11 1111 1111 1111 with
pin 8 tied low for straight binary/offset binary or between 00
0000 0000 0000 and 00 0000 0000 0001 with pin 8 tied high
for complementary binary/complementary offset binary.
Two’s complement coding requires using pin 31. With pin 8
tied low, adjust the gain trimpot until the output code flickers
equally between 01 1111 1111 1110 and 01 1111 1111
1111.
reference voltage source to obtain the output coding listed
in Table 3.
200ns max.
0 to +10V
Range
±5V
Input
Aquisition Time
150ns max.
Table 2. Zero and Gain Adjustments
35ns typ.
DATA N VALID
30ns max.
Zero Adjust
+1/2 LSB
N+1
+305µV
+305µV
FS – 1½ LSB
Gain Adjust
+9.999085V
+4.999085V
ADS-942