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RF2498
Rev A3 DS030711
7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical
support, contact RFMD at (+1) 336-678-5570 or sales-support@rfmd.com.
ISET Pins
ISET1 sets the internal reference voltage for the bias control circuits to all functional blocks. An external resistor of 5.1k
Ω to
ground is required. We do not recommend adjusting this resistor value. This resistor is pulled out to allow for a higher precision
off chip value and not as a significant tuning adjustment.
ISET2 sets the DC current through the LNAs in all bands when IPSET is high. Higher resistance to ground results in lower cur-
rent through the LNA. Increasing the LNA current will improve the IIP3 of the LNA and slightly increase gain in all modes. NF
typically will get worse as you increase current. Increasing the LNA current in one mode, i.e. Cellular, will also increase the LNA
current for the high IPSET state for PCS and the GPS LNAs as well.
ISET3 sets the DC current through the mixer and mixer preamplifier for all bands. Higher resistance to ground results in lower
current. Lower current will improve mixer NF but will degrade IIP3. Mixer and the mixer preamp gain is not significantly changed
with current.
Pin
Function
Type Description
Interface Schematic
28
GPS MIX IN
AI
GPS mixer RF single-end input.
29
VCC1
P
DC supply for internal reference, logic control, cellular mixer
preamp, and GPS mixer preamp (PCS mixer preamp has its’ own
DC supply, PCS_RFA_VCC). External bypass capacitor between
1nF and 47nF required.
30
ISET1
AO
Resistor for internal voltage reference setting. Recommended
value 5.1k
Ω.
31
ISET2
AO
Resistor to ground sets the LNA current in boost mode (all three
LNAs). Higher resistance results in lower current.
32
ISET3
AO
Resistor to ground sets preamp and mixer currents in all bands.
Higher resistance results in lower currents.
Pkg
Base
GND
P
Ground connection. The backside of the package should be sol-
dered to a top side ground pad which is connected to the ground
plane with multiple vias.
Legend:
DI=Digital Input from Baseband Chip
AI=Analog Input
AO=Analog Output
P=VCC or GND
GPS MIX IN
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