UM0890
User manual
2-stage RF power amplifier with LPF based on the
PD85006L-E and STAP85050 RF power transistors
Introduction
This user manual briefly describes the function and use of the STEVAL-TDR011V1
demonstration board.
The board is a two-stage 50 W RF power amplifier which includes an output LPF (low-pass
filter) for harmonics rejection. It also features power detection and a temperature sensor.
The main purpose of the board is to demonstrate the functioning and performance of the
PD85006L-E and the STAP85050 devices from the LdmoST plastic family of RF power
transistors.
The application is specifically designed for 2-way analog and digital mobile radios.
Figure 1.
STEVAL-TDR011V1 demonstration board
January 2010
Doc ID 16978 Rev 1
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c)
a)
Schematic diagram
d)
b)
Figure 2.
VR
Vdd
+5V
R1
R8
Jb
5
2
1
Vo
Vi
1
GND2
INHIBIT
3
Co
Ci
VGS1
VGS0
GND
R9
14
13
12
11
10
9
8
7
6
5
4
3
2
1
GND
J1
C9
R2 R7
C10
R10
C5
R4
R3
R6
R5
L1
GND
nc
INHIBIT
nc
nc
VP2
VP1
nc
V(T)
nc
nc
nc
VGS1
VGS0
INHIBIT
C4
C1
C2
C8
GND
1
C3
Pinout
power detector
voltage regulator
JP
2
low pass band filter
L2
Schematic diagram
C11
R11
C14b
TL10
C19
C22b
TL9
R14
C15
C18
TL11
TL13
PD2
C20
C16
C21
L5
C22a
L6
TL14
TL15
TL16
TL17
TL12
C6
C7
thermal temperature sensor
R12
R13
C14a
TL4
TL5
C17
TL6
PD85006L
The schematic diagram in
Figure 2
shows the following stages:
STEVAL-TDR011V1 demonstration board schematic
Doc ID 16978 Rev 1
PD1
VP2
VP1
Vo1
Vo2
TL3
P
ower Detector
TL18
Tx/Rx
Vo1
RF In
C12
L4
TL1
C2p
R4p
D1p
R3p R2p
L3
TL2
C13
C14
D2p
R1p
C1p
+ 5V
R7p
T
hermal
Sensor
R6p
C6p
C5p
C3p
C2f
C1f
R5p
C4p
F
ilter
Caf
Thermal
Sensor
R1t
C3f
V(T)
C2t
RF Ant
L3f
C6f
L2f
C5f
L1f
Cif
C1t
UM0890
UM0890
Testing procedure
2
2.1
Testing procedure
Equipment required
1.
2.
3.
4.
5.
DC power supply
RF power amplifier
RF signal generator
Power meters
Multimeter
2.2
Connector pin-out
Figure 3.
Pin-out scheme
2.3
Testing
To ensure the correct functioning of the STEVAL-TDR011V1, perform the following
procedure:
a)
b)
Connect a power supply with a high current capability (about 10 A) and set 13.6 V
on the drain.
The board features a voltage regulator (VR) to supply 5 V to a temperature sensor
(TS). Switch on the INHIBIT pin to activate the VR, and read the temperature with
the TS according to the following transfer function:
Equation 1
6
(
1.8639
–
V
o
)
-
T
= –
1481.96
+
2.1962
×
10
+ -----------------------------------
–
6
3.88
×
10
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Testing procedure
UM0890
The INHIBIT is not internally pulled up, and cannot be left floating. Disable the device when
connected to GND, or to a positive voltage less than 0.18 V.
c)
Select the bias gate mode by configuring the wires as shown in
Figure 6
and
Figure 7.
2.4
Thermal information
The temperature is taken on the surface of the PCB. If the PCB with its metal flange is
cooled using an additional heat-sink (Figure
5),
the main path of the heat (Pa) is easily
dissipated, maintaining the PCB temperature below 70 °C (Figure
4).
Figure 4.
Temperature trend
Figure 5.
PCB with an additional heat-sink
In
Figure 6,
the two wires are connected together in order to apply the same Vgg bias to
both stages of the amplifier.
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Doc ID 16978 Rev 1
UM0890
Figure 6.
Testing procedure
Bias mode selection - same Vgg bias to both amplifier stages
In
Figure 7,
the two wires must be open in order to apply two independent Vgg biases on
each stage of the amplifier.
Figure 7.
Bias mode selection - independent Vgg bias on each amplifier stage
Doc ID 16978 Rev 1
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