LTC1851 Linear Technology, LTC1851 Datasheet - Page 11

• Manufacturer Part Number: LTC1851
• Description: 1.25Msps Sampling ADCs
• Manufacturer: Linear Technology

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PI FU CTIO S
D9/S0 (Pin 23, LTC1851): Three-State Digital Data Out-
puts. Active when RD is low. Following a conversion, bit 9
of the present conversion is available on this pin. In
Readback mode, the end of sequence bit of the current
sequencer location (S0) is available on this pin. The output
swings between OV
D6 to D0 (Pins 24 to 30, LTC1850): Three-State Digital
Data Outputs. Active when RD is low. The outputs swing
between OV
D8 to D0 (Pins 24 to 32, LTC1851): Three-State Digital
Data Outputs. Active when RD is low. The outputs swing
between OV
NC (Pins 31, 32, LTC1850): No Connect. There is no
internal connection to these pins.
BUSY (Pin 33): Converter Busy Output. The BUSY output
has two functions. At the start of a conversion, BUSY will
go low and remain low until the conversion is completed.
The rising edge may be used to latch the output data. BUSY
will also go low while the part is in Program/Readback
mode (M1 high, M0 low) and remain low until M0 is
brought back high. The output swings between OV
OGND.
OGND (Pin 34): Digital Data Output Ground. Tie to analog
ground plane. May be tied to logic ground if desired.
OV
to 5V, can be used to interface with 3V digital logic. Bypass
to OGND with 10 F tantalum in parallel with 0.1 F ceramic
or 10 F ceramic. See Table 5.
M0 (Pin 36): Mode Select Pin 0. Used in conjunction with
M1 to select operating mode. See Table 5
PGA (Pin 37): Gain Select Input. A high logic level selects
gain = 1, a low logic level selects gain = 2.
U
DD
(Pin 35): Digital Data Output Supply. Normally tied
U
DD
DD
and OGND.
and OGND.
DD
U
and OGND.
DD
and
UNI/BIP (Pin 38): Unipolar/Bipolar Select Input. Logic low
selects a unipolar input span, a high logic level selects a
bipolar input span.
A0 to A2 (Pins 39 to 41): MUX Address Input Pins.
DIFF (Pin 42): Single-Ended/Differential Select Input. A
low logic level selects single-ended mode, a high logic
level selects differential mode.
WR (Pin 43): Write Input. In Direct Address mode, WR low
enables the MUX address and configuration input pins
(Pins 37 to 42). WR can be tied low or the rising edge of
WR can be used to latch the data. In Program mode, WR
is used to program the sequencer. WR low enables the
MUX address and configuration input pins (Pins 37 to 42).
The rising edge of WR latches the data and increments the
counter to the next sequencer location.
RD (Pin 44): Read Input. During normal operation, RD
enables the output drivers when CS is low. In Readback
mode (M1 high, M0 low), RD going low reads the current
sequencer location, RD high advances to the next sequencer
location.
CONVST (Pin 45): Conversion Start Input. This active low
signal starts a conversion on its falling edge.
CS (Pin 46): Chip Select Input. The chip select input must
be low for the ADC to recognize the CONVST and RD
inputs. If SHDN is low, a low logic level on CS selects Nap
mode; a high logic level on CS selects Sleep mode.
SHDN (Pin 47): Power Shutdown Input. A low logic level
will invoke the Shutdown mode selected by the CS pin. CS
low selects Nap mode, CS high selects Sleep mode. Tie
high if unused.
M1 (Pin 48): Mode Select Pin 1. Used in conjunction with
M0 to select operating mode.
LTC1850/LTC1851
11
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