LTC2205 Linear Technology, LTC2205 Datasheet - Page 17

• Manufacturer Part Number: LTC2205
• Description: (LTC2204 / LTC2205) 65Msps/40Msps
• Manufacturer: Linear Technology

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PIN FUNCTIONS
SENSE (Pin 1): Reference Mode Select and External
Reference Input. Tie SENSE to V
2.5V bandgap reference. An external reference of 2.5V or
1.25V may be used; both reference values will set a full
scale ADC range of 2.25V (PGA = 0).
V
mon mode. Must be bypassed to ground with a minimum
of 2.2µF . Ceramic chip capacitors are recommended.
V
Bypass to GND with 0.1µF ceramic chip capacitors.
GND (Pins 5, 8, 11, 15, 48, 49): ADC Power Ground.
A
A
ENC
sampled analog input is held on the rising edge of ENC
Internally biased to 1.6V through a 6.2kΩ resistor. Output
data can be latched on the rising edge of ENC
ENC
sampled analog input is held on the falling edge of ENC
Internally biased to 1.6V through a 6.2kΩ resistor. By-
pass to ground with a 0.1µF capacitor for a single-ended
Encode signal.
SHDN (Pin 16): Power Shutdown Pin. SHDN = low results
in normal operation. SHDN = high results in powered down
analog circuitry and the digital outputs placed in a high
impedance state.
DITH (Pin 17): Internal Dither Enable Pin. DITH = low
disables internal dither. DITH = high enables internal dither.
Refer to Internal Dither section of this data sheet for details
on dither operation.
D0-D15 (Pins 18-22, 26-28, 32-35 and 39-42): Digital
Outputs. D15 is the MSB.
OGND (Pins 23, 31 and 38): Output Driver Ground.
CM
DD
IN
IN
+
–
+
–
(Pin 2): 1.25V Output. Optimum voltage for input com-
(Pins 3, 4, 12, 13, 14): 3.3V Analog Supply Pin.
(Pin 6): Positive Differential Analog Input.
(Pin 7): Negative Differential Analog Input.
(Pin 10): Negative Differential Encode Input. The
(Pin 9): Positive Differential Encode Input. The
DD
to select the internal
+
.
+
–
.
.
OV
put Drivers. Bypass to ground with 0.1µF ceramic chip
capacitors.
CLKOUT
at the sample rate. Latch the data on the falling edge of
CLKOUT
CLKOUT
will toggle at the sample rate. Latch the data on the rising
edge of CLKOUT
OF (Pin 43): Over/Under Flow Digital Output. OF is high
when an over or under fl ow has occurred.
OE (Pin 44): Output Enable Pin. Low enables the digital
output drivers. High puts digital outputs in Hi-Z state.
MODE (Pin 45): Output Format and Clock Duty Cycle
Stabilizer Selection Pin. Connecting MODE to 0V selects
offset binary output format and disables the clock duty
cycle stabilizer. Connecting MODE to 1/3V
binary output format and enables the clock duty cycle sta-
bilizer. Connecting MODE to 2/3V
output format and enables the clock duty cycle stabilizer.
Connecting MODE to V
format and disables the clock duty cycle stabilizer.
RAND (Pin 46): Digital Output Randomization Selection
Pin. RAND low results in normal operation. RAND high
selects D1-D15 to be EXCLUSIVE-ORed with D0 (the
LSB). The output can be decoded by again applying an
XOR operation between the LSB and all other bits. This
mode of operation reduces the effects of digital output
interference.
PGA (Pin 47): Programmable Gain Amplifi er Control Pin. Low
selects a front-end gain of 1, input range of 2.25V
selects a front-end gain of 1.5, input range of 1.5V
GND (Exposed Pad, Pin 49): ADC Power Ground. The ex-
posed pad on the bottom of the package must be soldered
to ground.
DD
(Pins 24, 25, 36, 37): Positive Supply for the Out-
–
–
+
.
(Pin 29): Data Valid Output. CLKOUT
(Pin 30): Inverted Data Valid Output. CLKOUT
+
.
LTC2205/LTC2204
DD
selects 2’s complement output
DD
selects 2’s complement
DD
selects offset
–
will toggle
P-P
17
P-P
. High
22054fb
.
+