Rainbow-electronics MAX1208 Bedienungsanleitung PDF herunterladen (Seite 18)

MAX1208

for two’s complement (G/T = 0)

where CODE

is the decimal equivalent of the digital

output code as shown in Table 2.

Digital outputs D11–D0 are high impedance when the

MAX1208 is in power-down (PD = high). D11–D0 transi-

tion high 10ns after the rising edge of PD and become

active 10ns after PD’s falling edge.

Keep the capacitive load on the MAX1208 digital outputs

D11–D0 as low as possible (<15pF) to avoid large digital

currents feeding back into the analog portion of the

MAX1208 and degrading its dynamic performance. The

addition of external digital buffers on the digital outputs

isolates the MAX1208 from heavy capacitive loading. To

improve the dynamic performance of the MAX1208, add

220Ω resistors in series with the digital outputs close to

the MAX1208. Refer to the MAX1211 evaluation kit

schematic for an example of the digital outputs driving a

digital buffer through 220Ω series resistors.

Power-Down Input (PD)

The MAX1208 has two power modes that are controlled

with the power-down digital input (PD). With PD low, the

VV V V

CODE

INP INN REFP REFN

( ) −= − ××2

4096

12-Bit, 80Msps, 3.3V ADC

18 ______________________________________________________________________________________

GRAY CODE OUTPUT CODE (G/T = 1) TWO’S-COMPLEMENT OUTPUT CODE (G/T = 0)

BINARY

D11➝D0

DOR

HEXADECIMAL

EQUIVALENT

D11➝D0

DECIMAL

EQUIVALENT

D11➝D0

(CODE

)

BINARY

D11➝D0

DOR

HEXADECIMAL

EQUIVALENT

D11➝D0

DECIMAL

EQUIVALENT

D11➝D0

(CODE

)

INP

- V

INN

REFP

= 2.162V

REFN

= 1.138V

1000 0000 0000

0x800 +4095

0111 1111 1111 1

0x7FF +2047

>+1.0235V

(DATA OUT OF

RANGE)

1000 0000 0000

0x800 +4095

0111 1111 1111 0

0x7FF +2047 +1.0235V

1000 0000 0001

0x801 +4094

0111 1111 1110 0

0x7FE +2046 +1.0230V

1100 0000 0011

0xC03 +2050

0000 0000 0010 0

0x002 +2 +0.0010V

1100 0000 0001

0xC01 +2049

0000 0000 0001 0

0x001 +1 +0.0005V

1100 0000 0000

0xC00 +2048

0000 0000 0000 0

0x000 0 +0.0000V

0100 0000 0000

0x400 +2047

1111 1111 1111 0

0xFFF -1 -0.0005V

0100 0000 0001

0x401 +2046

1111 1111 1110 0

0xFFE -2 -0.0010V

0000 0000 0001

0x001 +1

1000 0000 0001 0

0x801 -2047 -1.0235V

0000 0000 0000

0x000 0

1000 0000 0000 0

0x800 -2048 -1.0240V

0000 0000 0000

0x000 0

1000 0000 0000 1

0x800 -2048

<-1.0240V

(DATA OUT OF

RANGE)

Table 2. Output Codes vs. Input Voltage

(

)

1 2 ... 13 14 15 16 17 18 19 20 21 22 23 ... 26 27

12-Bit, 80Msps, 3.3V ADC 1

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