MAX1497 Maxim, MAX1497 Datasheet - Page 13

• Manufacturer Part Number: MAX1497
• Description: 3.5- and 4.5-Digit / Single-Chip ADCs with LED Drivers and C Interface
• Manufacturer: Maxim

external-clock mode. When using the internal oscillator,
connect CLK to GND or DV
nect CLK to V
MAX1499 ideally operate with a 4.9152MHz clock to
achieve maximum rejection of 50Hz/60Hz common-
mode, power-supply, and normal-mode noise.
The MAX1497/MAX1499 contain an internal oscillator.
The power-up condition for the MAX1497/MAX1499 is
internal clock operation with the EXTCLK bit in the con-
trol register equal to zero. Using the internal oscillator
saves board space by removing the need for an exter-
nal clock source.
For external clock operation, set the EXTCLK bit in the
control register to one and drive CLK with a 4.9152MHz
clock source for best 50Hz/60Hz rejection ratio. Other
external clock frequencies allow for custom conversion
rates. A 2.4576MHz clock signal reduces the conver-
sion rate and the LED update rate by a factor of two
while keeping good 50Hz/60Hz noise rejection. The
MAX1497/MAX1499 operate with an external clock
source of up to 5.05MHz.
The MAX1497/MAX1499 contain an internal charge pump
to provide the negative supply voltage for the internal
analog input/reference buffers. The bipolar input range of
the analog input/reference buffers allows this device to
accept negative inputs with high source impedances.
Connect a 0.1µF capacitor from VNEG to GND.
Figure
2. Frequency Response of the SINC
3.5- and 4.5-Digit, Single-Chip ADCs with LED
-120
-160
-200
-40
-80
0
0
DD
______________________________________________________________________________________
for the MAX1497. The MAX1497/
10
20
FREQUENCY (Hz)
DD
30
for the MAX1499, or con-
External-Clock Mode
40
Internal-Clock Mode
4
Filter (Notch at 60Hz)
Charge Pump
50
60
Drivers and µC Interface
The MAX1499 has a 4.5-digit common-cathode display
driver and the MAX1497 has a 3.5-digit common-cath-
ode display driver.
schemes for a standard seven-segment LED display.
The LED update rate is 2.5Hz. The MAX1497/
MAX1499 automatically display the results of the ADC, if
desired
independent control of the LED driver through the serial
interface, allowing for data processing of the ADC result
before showing the result on the LED. Additionally, each
LED segment can be individually controlled (see the
LED segment-display register sections).
Figure
Figure
Table 1. LED Priority Table
X = Don’t care.
SEG_SEL SPI/ADC HOLD
F
1
0
0
0
0
DIGIT 4
D
3. Segment Connection for the MAX1499 (4.5 Digits)
4. Segment Connection for the MAX1497 (3.5 Digits)
A
G
F
(Table
DIGIT 3
D
A
G
C
B
DP
X
1
0
0
0
F
E
1). The MAX1497/MAX1499 also allow
DIGIT 3
C
B
G
D
DP
A
Figures 3 and 4
F
E
DIGIT 2
B
C
X
X
G
D
1
0
0
DP
A
E
F
B
C
DIGIT 2
A
G
D
DP
PEAK
E
F
X
X
X
1
0
C
B
DIGIT 1
A
G
DP
D
E
F
show the connection
DIGIT 1
C
B
LED segment
registers
LED display register
(user written)
LED display register
Peak register
ADC result register
A
G
DP
DISPLAY VALUES
D
E
F
B
DIGIT 0
C
A
G
D
DP
LED Driver
FORM
F
E
DIGIT 0
B
C
A
G
D
DP
C
B
DP
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