Rainbow Electronics MAX2338 - Manual (Page 9)

MAX2338
Triple/Dual-Mode CDMA LNA/Mixers
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Detailed Description
The MAX2338 consists of cellular band and PCS band
(LNAs) and mixers. The IC also consists of a local oscil-
lator (LO) divider and LO buffers for cellular and PCS
bands.
Low-Noise Amplifiers
The MAX2338 LNAs’ gain and linearity are switched by
the GAIN and LIN input, respectively. The PCS band
LNA has two operational modes: high-gain high-linearity
(HGHL) and high-gain low-linearity (HGLL). The cellular
band LNA has three operational in modes: HGHL, HGLL,
and low-gain high-linearity (LGHL) modes. The table in
the
Operational Modes section shows the pin settings for
BAND, GAIN, and LIN for various operating modes. Use
HGHL mode when extra high linearity is required for
cross-modulation suppression, HGLL mode when the
transmitter is off and cross-modulation is not a concern,
and LGHL mode when receiving large signals.
Downconverter
The downconverters in these devices are double bal-
anced mixers. The PCS band mixer and digital cellular
band mixer share the same IF output ports. The cellular
FM band mixer has its own IF output to feed to a different
filter. When the linearity requirement is high, the LIN con-
trol input increases the current in the downconverter. The
downconverter requires a DC blocking capacitor at the
input and output, and a pullup inductor at the output. The
DC blocking capacitors can be designed to be part of
the matching circuits. The table in the Operational
Modes section shows the settings for
BAND, GAIN, and
LIN for various operating modes.
LO Output Buffers
There are two LO output buffers: cellular and PCS. The
inputs are tied together and internally matched to 50
Ω.
The outputs of the PCS and cellular buffers are brought
out separately. The outputs of the buffers are internally
matched and include a DC blocking capacitor.
LO Divider
The MAX2338 includes an LO divider circuit which
enables a single VCO for both cellular and PCS bands.
The LO/2 logic input turns the divider on or off in the cel-
lular band.
FUNCTION CONTROL PIN
MODES
BAND (H/L) LOX1 LO /2 HGHL Amp HGLL Amp LGHL Amp CDMA HL Mixer CDMA LL Mixer FM Mixer BAND GAIN LIN LO/2
PCS Band, High-Gain, High-Linearity (HGHL) H ✓ ✓ ✓ 0 1 1 X
PCS Band, High-Gain, Low-Linearty (Idle Mode) (HGLL) H ✓ ✓ ✓ 0 1 0 X
Undefined — — — — — — — — — 0 0 1 X
Cellular Band CDMA, High-Gain, High-Linearity (HGHL) L ✓ ✓ ✓ 1 1 1 1
Cellular Band CDMA, High-Gain, Low-Linearity (Idle Mode)
(HGLL)
L ✓ ✓ ✓ 1 1 0 1
Cellular Band, CDMA, Low-Gain L ✓ ✓ ✓ 1 0 1 1
Cellular Band, FM Mode L ✓ ✓ ✓ 1 0 0 1
Cellular Band CDMA, High-Gain, High-Linearity (HGHL) L ✓ ✓ ✓ 1 1 1 0
Cellular Band CDMA, High-Gain, Low-Linearity (Idle Mode)
(HGLL)
L ✓ ✓ ✓ 1 1 0 0
Cellular Band, CDMA, Low-Gain L ✓ ✓ ✓ 1 0 1 0
Cellular Band, FM Mode L ✓ ✓ ✓ 1 0 0 0
Shutdown 0 0 0 X
Table 1. Operational Modes