LTC2171-14_15 Datasheet, PDF (28/34 Pages) Linear Technology – 14-Bit, 65Msps/40Msps/ 25Msps Low Power Quad ADCs

LTC2172-14/
LTC2171-14/LTC2170-14
Applications Information
GROUNDING AND BYPASSING
The LTC2172-14/LTC2171-14/LTC2170-14 requires a
printed circuit board with a clean unbroken ground plane.
A multilayer board with an internal ground plane in the
first layer beneath the ADC is recommended. Layout for
the printed circuit board should ensure that digital and
analog signal lines are separated as much as possible. In
particular, care should be taken not to run any digital track
alongside an analog signal track or underneath the ADC.
High quality ceramic bypass capacitors should be used at
the V_DD, OV_DD, V_CM, V_REF, REFH and REFL pins. Bypass
capacitors must be located as close to the pins as possible.
Of particular importance is the 0.1µF capacitor between
REFH and REFL. This capacitor should be on the same
side of the circuit board as the A/D, and as close to the
device as possible (1.5mm or less). Size 0402 ceramic
capacitors are recommended. The larger 2.2µF capacitor
between REFH and REFL can be somewhat further away.
The traces connecting the pins and bypass capacitors must
be kept short and should be made as wide as possible.
The analog inputs, encode signals and digital outputs
should not be routed next to each other. Ground fill and
grounded vias should be used as barriers to isolate these
signals from each other.
HEAT TRANSFER
Most of the heat generated by the LTC2172-14/LTC2171-14/
LTC2170-14 is transferred from the die through the bottom-
side exposed pad and package leads onto the printed circuit
board. For good electrical and thermal performance, the
exposed pad must be soldered to a large grounded pad
on the PC board. This pad should be connected to the
internal ground planes by an array of vias.
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