LTC5549
16
5549fa
For more information www.linear.com/LTC5549
applicaTions inForMaTion
Enable Interface
Figure 9 shows a simplified schematic of the EN pin in-
terface. To enable
the chip, the EN voltage must be higher
than 1.2V. The voltage at the EN pin should never exceed
V
CC
by more than 0.3V. If this should occur, the supply
current could be sourced through the ESD diode, potentially
damaging the IC. If the EN pin is left floating, its voltage
will be pulled low by the internal pull-down resistor and
the chip will be disabled.
X2 Interface
Figure 10 shows a simplified schematic of the X2 pin
interface. To enable the integrated LO frequency doubler,
Figure 9. Simplified Enable Input Circuit Figure 10. Simplified X2 Interface Circuit
the X2 voltage must be higher than 1.2V. The X2 voltage
at the pin should never exceed V
CC
by more than 0.3V. If
this should occur, the supply current could be sourced
through the ESD diode, potentially damaging the IC. If the
X2 pin is left floating, its voltage will be pulled low by the
internal pull-down resistor and the LO frequency doubler
will be disabled.
Supply Voltage Ramping
Fast ramping of the supply voltage can cause a current
glitch in the internal ESD protection circuits. Depending on
the supply inductance, this could result in a supply volt-
age transient
that exceeds the maximum rating. A supply
voltage ramp time of greater than 1ms is recommended.
LTC5549
EN
5549 F09
7
V
CC
9
BIAS
LTC5549
X2
5549 F10
8
V
CC
9
