TQ5135 View Datasheet(PDF) - TriQuint Semiconductor
Part Name
Description
Manufacturer
TQ5135 Datasheet PDF : 22 Pages
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Pinout Description:
The TQ5135 is a complete front-end for a low band CDMA
handset receiver. It combines a high IP3 low noise amplifier,
a high intercept mixer, and an IF amplifier. The LNA uses an
off-chip matching network, which connects to the input at pin
2. The amplifier was designed so that the match for maximum
gain also gives very low noise figure. The LNA has two
modes, high gain and bypass. Pin 15 is the input to the gain
control logic, which drives the switch FETs. In the high gain
mode (pin 15=low), the LNA provides around 17dB of gain. In
the bypass mode (pin 15=high) it has a loss of about 2dB.
The LNA also provides several ways of setting gain and
intercept in the design phase. The LNA FET source is
brought out to Pin 16, where a small value of inductance to
ground can be added. The inductor can be discrete or simply
a small length of pc board trace. Several dB of adjustment is
possible. A bias resistor on pin 4 is used to set the LNA supply
current. A nominal value of 2.7kohm is recommended, but it
can be increased for lower LNA Idd.
The LNA output signal is at Pin 14. It is a 50 ohm line and can
be connected directly to a SAW image filter. The image filter
output connects to the mixer input at Pin 12. The mixer
receives its LO via a buffer which amplifies the signal from Pin
9. The drain of buffer transistor is connected to Pin 10 where
it is connected to an external LO tuning inductor.
GND/LNA
LNA
Gain
Mode
LNA Out
N/C
1
GND
logic
MXR In
RF In
GND
LNA
Bias
LNA
active
bias
Mixer
IF Amp
LO Buffer
GND
LO
Vdd
LO
In
LNA Vdd
GND
IF Out
GIC
Figure 1. TQ5135 Block diagram
TQ5135
Data Sheet
The IF signal from the mixer is fed to an amplifier. The IF
amplifier is an open drain type with output at Pin 7. An
external matching circuit is required to match the IF output to
a filter. The IF amplifier also has a GIC pin (Gain-Intercept-
Current). It is used to set the DC current and gain of the IF
stage.
Application Information:
Half IF Spur Rejection Considerations:
The TQ5135 does not contain a balanced mixer so Half-IF
spur rejection is completely set by the image filter. Thus we
do not recommend using an IF that is less than 2.5 times the
image filter.
Grounding:
With good layout techniques there should not be any stability
problems. Poor circuit board design can result in a circuit that
oscillates. Good grounding is especially important for the
TQ5135 since it uses an outboard LO tuning inductor that
provides one more potential ground loop path. One could
use the evaluation board as an example of proper layout
techniques.
It is important to position the LO tuning, GIC, and IF matching
components as close to the chip as possible. If the
components are far enough away they and their
corresponding pc board traces can act as quarter wave
resonators in the 5-10Ghz region. If both the IF and the LO
paths to ground resonate at the same frequency, oscillation
can result.
It is most important that the ground on the GIC bypass cap,
the ground on the LO tuning bypass capacitor, and the IF
shunt cap ground return back to the chip grounds with minimal
inductance (Figure 2).
Also, improving the ground at the LO tuning inductor bypass
cap will increase circuit Q. Thus mixer drive is improved with
a resultant higher IP3. Improved ground here means minimal
inductance between the chip ground pins and the other
ground return points.
For additional information and latest specifications, see our website: www.triquint.com
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