LTC2600 Linear Technology, LTC2600 Datasheet - Page 12

• Manufacturer Part Number: LTC2600
• Description: (LTC2600 - LTC2620) 3V/5V Octal 12-bit Rail-to-rail DAC
• Manufacturer: Linear Technology

LTC2600/LTC2610/LTC2620
OPERATIO
DC output impedance is equivalent to load regulation, and
may be derived from it by simply calculating a change in
units from LSB/mA to Ohms. The amplifiers’ DC output
impedance is 0.025 when driving a load well away from
the rails.
When drawing a load current from either rail, the output
voltage headroom with respect to that rail is limited by the
25 typical channel resistance of the output devices; e.g.,
when sinking 1mA, the minimum output voltage = 25 •
1mA = 25mV. See the graph Headroom at Rails vs Output
Current in the Typical Performance Characteristics sec-
tion.
The amplifiers are stable driving capacitive loads of up to
1000pF.
12
U
Board Layout
The excellent load regulation and DC crosstalk perfor-
mance of these devices is achieved in part by keeping
“signal” and “power” grounds separated internally and by
reducing shared internal resistance to just 0.005 .
The GND pin functions both as the node to which the
reference and output voltages are referred and as a return
path for power currents in the device. Because of this,
careful thought should be given to the grounding scheme
and board layout in order to ensure rated performance.
The PC board should have separate areas for the analog
and digital sections of the circuit. This keeps digital signals
away from sensitive analog signals and facilitates the use
of separate digital and analog ground planes which have
minimal capacitive and resistive interaction with each
other.
Digital and analog ground planes should be joined at only
one point, establishing a system star ground as close to
the device’s ground pin as possible. Ideally, the analog
ground plane should be located on the component side of
the board, and should be allowed to run under the part to
shield it from noise. Analog ground should be a continu-
ous and uninterrupted plane, except for necessary lead
pads and vias, with signal traces on another layer.
2600f