A920:
WCDMA RX Downconverter (MAX2388)
Description
The first IC in the WCDMA Rx line up is U310 (MAX2388), which is an LNA and down converter mixer combination. The RX frequency will be mixed down to an IF
frequency of 190MHz. The MAX2388 also has a shutdown mode to power down the IC, via MAX2388_SHDN*, during the front-end receiver‘s idling period to con-
serve battery life. U310 operates from the PCAP supply voltage RC_VCCA (derived from VRF_RX_2_775V). The nominal gain expect is ~15dB.
U310 operates in high gain mode selectable from RX_RF_ATTEN by the HARMONY_LITE . The nominal gain expected while in this mode is 15dB. During high
input signal levels the LNA will be off.
The receive mixer is a wideband, single-balanced design. The input RF_LO (pin #5) receives the VCO frequency (2330 - 2360MHz) through FL310 from U140 (VCO).
The RF input (LNA_IN, pin #10) receives the RX frequency (2110 - 2170MHz) from FL002.
The MIX_IN (pin #3) input is connected to LNAOUT (pin #1) through FL300. The function of FL300 is to provide image rejection and out-of-band interferers filtering.
The frequency conversion process performed by the mixer / oscillator combination sometimes will allow a frequency other than desired frequency to be fed into the IF
and subsequently amplified.
The IF mixer output (190MHz) appears on the differential IFPOS (pin #8) and IFNEG (pin #7). These open-collector outputs require an external inductor (L320 & L321)
to VCC for DC biasing.
The 190MHz IF frequency passes through FL320. The IF SAW filter has a nominal center frequency of 190MHz and a bandwidth of 3.84MHz. Between the input
match (C323, C324 & L322), output match (L327, L328, C328, C329, & C325) and the filter (FL320)- the expected nominal losses is ~10dB.
Motor
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4-
16
RX_RF_ATTEN
WCDMA_RX
RF_LO
FL310
MAX2388_SHDN*
FL300
FL320
Harmony
Lite
MAX2309
U310
CDMAPOS
CDMANEG
WCDMA
VCO
