CMX901

CML Microcircuits
RF Power Amplifier
COMMUNICATION SEMICONDUCTORS

Broadband Efficient RF Power Amplifier

D/901/6 April 2020 DATASHEET Provisional Information

Features Applications
 Wide operating frequency range  Wireless data communications
130MHz to 950MHz FSK, FFSK/MSK, GFSK/GMSK, Multi-level FSK
 Typical output power:  Analogue FM handheld radio terminals
• 2.5W operating at 160MHz  Marine AIS Class-B and Marine AIS-SART
• 1.8W operating at 435MHz
 RFID readers/writers
• 1.5W operating at 915MHz
 Automatic meter reading (AMR)
 High power gain 40dB
 Wireless sensor networks
 High power added efficiency
Mesh/Ad hoc systems
up to 60% at VHF
 Remote control and sensing systems
 Single polarity supply voltage
2.5V to 6V  Commercial and consumer communications
 Small 28 pin WQFN package
VDD2
VGS2

VGS3

VDD1

RFOUT

RFIN RFOUT

PAPA
11 PA 2 PA 3 RFOUT

RFIN RFOUT

CMX901 RFOUT
VGS1

VA

1 Brief Description
The CMX901 is a three stage high-gain and high efficiency RF power amplifier. The device is ideally suited for use in VHF
and UHF frequency bands up to 950MHz.

The first and second stages of the amplifier operate in a class-A and class-AB mode respectively, and the third stage
operates in a class-C mode for maximum efficiency.

External components are required to match the device input and output ports to 50 Ohms. The CMX901 is available in a
small footprint 5mm x 5mm, low thermal resistance 28-pin WQFN package making it ideal for small form factor
applications such as data modules as well as handheld radio terminals.

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RF Power Amplifier CMX901

CONTENTS
Section Page
1 Brief Description....................................................................................................................................................... 1
1.1 History ...................................................................................................................................................................... 3
2 Block Diagram .......................................................................................................................................................... 3
3 Performance Specification ........................................................................................................................................ 4
3.1 Electrical Performance .............................................................................................................................................. 4
3.1.1 Absolute Maximum Ratings ....................................................................................................................................... 4
3.1.2 Operating Limits........................................................................................................................................................ 4
3.1.3 Operating Characteristics .......................................................................................................................................... 5
3.2 Typical Performance.................................................................................................................................................. 6
3.2.1 Operation at 160MHz ................................................................................................................................................ 6
3.2.2 Operation at 435MHz ................................................................................................................................................ 7
3.2.3 Operation at 915MHz ................................................................................................................................................ 8
4 Pin and Signal Definitions ......................................................................................................................................... 9
4.1 Pin List ...................................................................................................................................................................... 9
4.2 Signal Definitions .................................................................................................................................................... 10
5 Application Information ......................................................................................................................................... 11
5.1 General Description ................................................................................................................................................ 11
5.2 Main Characteristics................................................................................................................................................ 11
5.2.1 Input Impedance ..................................................................................................................................................... 11
5.2.2 Thermal Design ....................................................................................................................................................... 12
6 General Application Schematic ............................................................................................................................... 13
7 PCB Layout ............................................................................................................................................................. 14
8 Application Notes ................................................................................................................................................... 14
8.1 Output Power Control ............................................................................................................................................. 14
8.1.1 TDMA Operation ..................................................................................................................................................... 14
9 Packaging ............................................................................................................................................................... 15
9.1 Ordering ................................................................................................................................................................. 15

Table Page

Table 1 S-parameter data (S11), VDD = 4V, Vgs1 = 1.65V, Vgs2 = 1.35V and Vgs3 = 0.93V, Ids = 18mA .......................................... 12
Table 2a Recommended External Components (variations with frequency) ............................................................................... 14

Figure Page

Figure 1 CMX901 Block Diagram ................................................................................................................................................. 3

Figure 2 Input power to output power characteristic, VDD = 4V .................................................................................................... 6
Figure 3 Variation of output power with temperature, V DD = 4V, VPARAMP = 3.3V, input level = -5dBm .................................... 6
Figure 4 Output power vs. control voltage characteristics and variation with temperature, V DD = 4V, input level = -5dBm ............. 6
Figure 5 Output power and efficiency variation with temperature, V DD = 4V, input level = -5dBm, VPARAMP = 3.3V .......................... 6
Figure 6 Input power to output power characteristic, V DD = 4V at 435MHz ................................................................................... 7
Figure 7 Variation in output power with temperature, V DD = 4V, VPARAMP = 3.3V, input level = -10dBm .......................................... 7
Figure 8 Output power vs. control voltage characteristics variation with temperature, V DD = 4V, input level = -10dBm.................. 7
Figure 9 Output power and efficiency variation with temperature, V DD = 4V, input level = -10dBm, VPARAMP = 3.3V ........................ 7
Figure 10 Input power to output power characteristic, V DD = 4V at 915MHz ................................................................................. 8
Figure 11 Variation in output power with temperature, V DD = 4V, VPARAMP = 3.3V, input level = 0dBm ........................................... 8
Figure 12 Output power vs. control voltage characteristics variation with temperature, V DD = 4V, input level = 0dBm ................... 8
Figure 13 Output power and efficiency variation with temperature, V DD = 4V, input level = 0dBm, VPARAMP = 3.3V ......................... 8
Figure 14 Pin Configuration......................................................................................................................................................... 9
Figure 15 S11 response, VDD = 4V, Vgs1 = 1.65V, Vgs2 = 1.35V and Vgs3 = 0.93V, Ids = 18mA ........................................................ 11
Figure 16 CMX901 Recommended External Components........................................................................................................... 13
Figure 17 QT8 Mechanical Outline ............................................................................................................................................ 15

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RF Power Amplifier CMX901

1.1 History
Version Changes Date
nd
6 Section 3.1.3.1: addition to table describing enhanced input power range 22 April 2020
condition for stability performance at 160 MHz.
5 R2 = 200 Ohms for VHF applications 9th August 2019
Section 3: Thermal data added
th
4 Section 5.2.2: Thermal Design added 19 July 2017
Datasheet changed to Provisional status
th
3 Section 5.2.1: Updated s-parameter data in Table 1 9 February 2017
th
2 First public release 7 February 2017
1 Internal release January 2017

This is Provisional Information; changes and additions may be made to this specification. Parameters marked TBD or left
blank will be included in later issues.

2 Block Diagram
VDD2
VGS2

VGS3
NC

NC

NC

NC
28

27

26

25

24

23

22
VDD1 1 21 NC

NC 2 20 RFOUT

RFIN 3 19 RFOUT

NC 4 PAPA
11 PA12 PA 3 18 RFOUT

RFIN 5 17 RFOUT

NC 6 CMX901 16 RFOUT

NC 7 15 NC
10

11

12

13

14
8

9
VGS1

NC

NC

NC

NC

NC

VA

Figure 1 CMX901 Block Diagram

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RF Power Amplifier CMX901

3 Performance Specification
3.1 Electrical Performance
3.1.1 Absolute Maximum Ratings
Exceeding these maximum ratings can result in damage to the device.

Notes Min. Max. Unit

Supply: VDD - VSS 1 -0.5 12.0 V
IDD - ISS 2 2.2 A
RF power at input pin 1 15 dBm
Output load VSWR 10:1
RF Power per pin 30 dBm
Notes
1. Transient and not operational i.e. Vgs1, Vgs2 and Vgs3 set to 0V
2. Rating for peak or continuous operation

QT8 Package (28-pin WQFN) Notes Min. Max. Unit

Storage Temperature -50 +125 °C

3.1.2 Operating Limits

Correct operation of the device outside these limits is not implied.

Notes Min. Max. Unit

Supply Voltage:
VDD – VSS 2.5 6 V
VGS – VSS (per stage) 2.5 V

Operating Air Temperature (TAMB) -40 +85 °C

Maximum Allowable Junction Temperature +125 °C
Maximum Continuous Power Dissipation (PDISS ) 3, 4 1.8 W

Notes
3. Dependent on PCB layout arrangements and heatsinking, see section 5.2.2.
4. PDISS= PDC–POUT , where: PDC = VDD x IDD and POUT = measured RF output power.

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3.1.3 Operating Characteristics

For the following conditions unless otherwise specified: External components as recommended in
Figure 16, VDD = 4.0V
TAMB = 25°C, VBIAS = 3.3V
Specification Min. Typ. Max. Unit Condition
RF Frequency Range 130 - 950 MHz
Quiescent Current (from VDD) - - 1 µA VBIAS = VPARAMP = 0V
Thermal Resistance RJC (junction to - 2.5 3 °C/W
central heatsink ground pad)

3.1.3.1 Operating Characteristics 160MHz

RF frequency = 160MHz, RF power input = -5dBm, VPARAMP = 3.3V
Specification Min. Typ. Max. Unit Condition
Maximum output power (Pmax160) - 2.5 - W Pin = -5dBm
Power added efficiency - 61 - % Pout = 2.5W, VDD = 4V
Input power for Pmax160 - -5 - dBm VDD = 4V
Gain - 39 - dB Pin = -5dBm
- 45 - dB Pin = -15dBm
Second harmonic - -23 - dBc Pmax 160
Third harmonic - -37 - dBc Pmax 160
Fourth harmonic - -54 - dBc Pmax 160
Other non-harmonic spurious - - -75 dBc Pmax 160
Input VSWR See s11
- - See section 5.2.1
data
Stability, VSWR 5:1 Stable all phases, continuous or Variation from normal
pulsed operation, power output output power with 50Ω
variation with load phase +1,-4 dB load and with input power
(typ.) (Pin) between -15 dBm and
0 dBm.
Open circuit, Short circuit No Continuous operation for
damage 30 seconds

3.1.3.2 Operating Characteristics 435MHz

RF frequency = 435MHz, RF power input = -10dBm, VPARAMP = 3.3V
Specification Min. Typ. Max. Unit Condition
Maximum output power (Pmax435) - 1.8 - W Pin = -5dBm
Power added efficiency - 52 - % Pout = 1.8W, VDD = 4V
Input power for Pmax435 - -10 - dBm VDD = 4V
Gain - 42.5 - dB
ACPR EN 300 086, 25kHz
- - -70 dBc
channel
Reverse Isolation - -60 - dB Pmax 435
Second harmonic - -30 - dBc Pmax 435
Third harmonic - -52 - dBc Pmax 435
Fourth harmonic - -46 - dBc Pmax 435
Other non-harmonic spurious - - -75 dBc Pmax 435
Input VSWR See s11 See section 5.2.1
- -
data
Stability, VSWR 5:1
Stable all phases, continuous
operation, power output
variation with load phase ±2dB
(typ.)

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RF Power Amplifier CMX901

Open circuit, Short circuit No damage Continuous operation

for 30 seconds

3.1.3.3 Operating Characteristics 915MHz

RF frequency = 915MHz, RF power input = 0dBm, VPARAMP = 3.3V
Specification Min. Typ. Max. Unit Condition
Maximum output power (Pmax915) - 1.5 - W VDD = 4V
Power added efficiency - 42 - % Pout = 1.5W, VDD = 4V
Input power for Pmax915 - 0 - dBm
Gain - 32 - dB Pin = 0 dBm
- 31 - dB Pin = -10 dBm
Second harmonic - -45 - dBc Pmax915
Third harmonic - -54 - dBc Pmax915
Fourth harmonic - -52 - dBc Pmax915
Other non-harmonic spurious - - -75 dBc Pmax915
Input VSWR See s11
- -
data
Stability, VSWR 3:1 Stable all phases, continuous
operation, power output variation
with load phase ±2 dB (typ.)
Stability, VSWR 10:1 Stable all phases
Open circuit, Short circuit No damage Continuous operation for 30s

3.2 Typical Performance

3.2.1 Operation at 160MHz
Performance data measured using EV9011 PCB, circuit values as Table 2 / Figure 16.

Figure 2 Input power to output power characteristic, Figure 3 Variation of output power with temperature,
VDD = 4V VDD = 4V, VPARAMP = 3.3V, input level = -5dBm

Figure 4 Output power vs. control voltage Figure 5 Output power and efficiency variation with
characteristics and variation with temperature, temperature, VDD = 4V, input level = -5dBm, VPARAMP = 3.3V
VDD = 4V, input level = -5dBm

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RF Power Amplifier CMX901

3.2.2 Operation at 435MHz

Performance data measured using EV9011 PCB, circuit values as Table 2 / Figure 16.

Figure 6 Input power to output power characteristic, Figure 7 Variation in output power with temperature,
VDD = 4V at 435MHz VDD = 4V, VPARAMP = 3.3V, input level = -10dBm

Figure 8 Output power vs. control voltage characteristics Figure 9 Output power and efficiency variation with
variation with temperature, VDD = 4V, temperature, VDD = 4V, input level = -10dBm,
input level = -10dBm VPARAMP = 3.3V

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RF Power Amplifier CMX901

3.2.3 Operation at 915MHz

Performance data measured using EV9011 PCB, circuit values as Table 2 / Figure 16.

Figure 10 Input power to output power characteristic, Figure 11 Variation in output power with temperature,
VDD = 4V at 915MHz VDD = 4V, VPARAMP = 3.3V, input level = 0dBm

Figure 12 Output power vs. control voltage characteristics Figure 13 Output power and efficiency variation with
variation with temperature, VDD = 4V, input level = 0dBm temperature, VDD = 4V, input level = 0dBm, VPARAMP = 3.3V

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RF Power Amplifier CMX901

4 Pin and Signal Definitions

Top View

VDD2
VGS2

VGS3
NC

NC

NC

NC
28

27

26

25

24

23

22
VDD1 1 21 NC

NC 2 20 RFOUT

RFIN 3 19 RFOUT

NC 4 Exposed Metal Pad 18 RFOUT

RFIN 5 17 RFOUT

NC 6 16 RFOUT

NC 7 15 NC
10

11

12

13

14
8

9
VGS1

NC

NC

NC

NC

NC

VA
GND

Figure 14 Pin Configuration

4.1 Pin List

Pin No. Pin Name Type Description

1 VDD1 PWR Power supply for the first stage

2 NC NC Connect to GND
3 RFIN IP RF signal input (off-chip DC blocking capacitor required)
4 NC NC Connect to ground
5 RFIN IP As pin 3
6 NC NC Connect to GND
7 NC NC Connect to GND
8 VGS1 IP Bias input for first stage
9 NC NC Connect to GND
10 NC NC Connect to GND
11 NC NC Connect to GND
12 NC NC Connect to GND
13 NC NC Connect to GND
14 VA PWR Connect to 3.3V
15 NC NC Connect to GND
16 RFOUT
17 RFOUT
18 RFOUT OP Power supply and RF output
19 RFOUT
20 RFOUT
21 NC NC Connect to GND
22 NC NC Connect to GND
23 NC NC Connect to GND
24 VGS3 IP Bias input for output stage

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RF Power Amplifier CMX901

Pin No. Pin Name Type Description

25 NC NC Connect to GND
26 VDD2 PWR Power supply for second stage
27 NC NC Connect to GND
28 VGS2 IP Bias input for second stage
Exposed Metal The central metal pad must be connected to ground.
GND PWR
Pad

Notes:
OP = Output PWR = Power Connection
IP = Input NC = No internal connection

4.2 Signal Definitions

Signal
Pins Usage
Name
VDD VDD Power supply
VGS1 VGS1 Bias input for the first amplifier stage
VGS2 VGS2 Bias input for the second amplifier stage
VGS3 VGS3 Bias input for the third amplifier stage
VPARAMP N/A Combined control voltage with VGS1 VGS2 configured as
Figure 16 (NB: see also section 8.1).
VBIAS N/A Combined control voltage VGS3 and pin VA, configured as
Figure 16.
Vss GND Ground

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RF Power Amplifier CMX901

5 Application Information
5.1 General Description
The CMX901 is a three-stage RF power amplifier producing high gain at full output power. An input power of up to 0dBm
is required to achieve fully-saturated output power (0dBm at maximum operating frequency). The device requires only a
single positive power supply. The primary ground connection is via a large central pad on the bottom of the package.
.
The first and second stages of the amplifier operate in class-A and class-AB mode, respectively. The final stage operates in
Class-C mode. DC current will increase with RF input signal. The optimum load for maximum output power and efficiency
is approximately 5Ω. An external matching network is required to match this impedance to a 50Ω load (see Figure 16).
The RFIN pins are DC biased, thus a blocking capacitor is recommended between signal source and the input pins.

Vdd1 and Vdd2 provide DC power supply to the first and second stages, respectively. An RF tuning inductor is needed for
each pin. Vgs1, Vgs2 and Vgs3 should be set to different bias voltages for maximum output power and efficiency; see
Figure 16 and section 8.1 for further details.

5.2 Main Characteristics

5.2.1 Input Impedance
Typical CMX901 input impedance (S11) is shown in Figure 15 as measured with EV9011 configured for 435MHz operation
with a RC network of 470R and 1nF (but no other matching) at the input. The measured S11 response varies with inter-
stage and output matching configuration. The configuration used for this measurement was the 435MHz circuit values
from Figure 16 / Table 2.

Figure 15 S11 response, VDD = 4V, Vgs1 = 1.65V, Vgs2 = 1.35V and Vgs3 = 0.93V, Ids = 18mA

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RF Power Amplifier CMX901

Frequency (MHz) S(1,1) Mag ∠Ang

100 0.796 ∠- 9.537°
150 0.805 ∠- 13.911°
200 0.811 ∠- 18.941°
250 0.825 ∠- 24.26°
300 0.843 ∠- 30.397°
350 0.872 ∠- 38.211°
400 0.859 ∠- 50.154°
450 0.822 ∠- 55.754°
500 0.809 ∠- 63.538°
550 0.747 ∠- 72.205°
600 0.683 ∠- 76.943°
650 0.641 ∠- 80.317°
700 0.628 ∠- 82.409°
750 0.633 ∠- 85.03°
800 0.647 ∠- 89.029°
850 0.657 ∠- 93.691°
900 0.665 ∠- 98.609°
950 0.668 ∠- 103.614°
1000 0.671 ∠- 107.921°
Table 1 S-parameter data (S11), VDD = 4V, Vgs1 = 1.65V, Vgs2 = 1.35V and Vgs3 = 0.93V, Ids = 18mA
5.2.2 Thermal Design
The large central pad on the bottom of the package should be electrically and thermally connected to the PCB ground
plane, typically with 20-25 vias, a 0.2mm hole size is recommended and the vias must be from top layer to bottom layer.
A typical solution is a via pattern based on an inner via diameter of 0.200mm (0.025mm plating of via walls), with 25 vias
on a 0.670mm grid pattern; the vias do not need to be filled. The PCB layout should provide a thermal radiator
appropriate for the intended operation/duty cycle in order to avoid an excessive junction temperature.

It should be noted that the peak power dissipation may exceed the maximum rated continuous power dissipation (PDISS )
when the transmitter is used for discontinuous transmission for example in TDMA transmission systems. In this case
average power dissipation should not exceed P DISS.

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RF Power Amplifier CMX901

6 General Application Schematic

VDD

C1

GND

C4 C5 C2 C3 C6 C7
L2 R2 L1 R1 L3
C20
GND GND GND

Vgs2 Vgs3

28
27
26
25
24
23
22
VGS2
NC
VDD2
NC
VGS3
NC
NC
1 21
VDD1 NC
2 20
NC RFOUT
3 19
RFIN RFOUT
C9 L4 4 18 L5 C8
Exposed
RFIN NC RFOUT RFOUT
5 Metal Pad 17
C21 C22 RFIN RFOUT C10 C11 C12
6 16
R3 NC RFOUT
7 15
NC NC
C23
VGS1

GND
NC
NC
NC
NC
NC
VA
8
9
10
11
12
13
14

GND
C24

Vgs1
GND

VPARAMP Vbias

R7 R5 R6
R8
Vgs1 Vgs2 Vgs3

R10 C26 R9 C25 R11 C19

GND GND GND

Figure 16 CMX901 Recommended External Components

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RF Power Amplifier CMX901

L1 L2 L4
Frequency L3 L5 C21 C22 C10 C11 C12
(0603CS) (0603CS) (0630CS)
(MHz) (nH) (nH) (pF) (pF) (pF) (pF) (pF)
(nH) (nH) (nH)
160 56 56 19 150 12 - 3.3 12 56 5.6
435 27 27 16 43 3.6 5.6 - 4.7 - 18
915 5.6 8.7 6 10 1.8 4.7 - 10 4.7 -
Table 2a Recommended External Components (variations with frequency)

R1 N/F C1 4.7µF C19 100pF

R2 N/F (Note 4) C2 Note 1 C20 N/F
R3 680 (Note 2) C3 1uF C21 Table 2a
R5 68k C4 Note 1 C22 Table 2a
R6 100k C5 1uF C23 1nF
R7 68k C6 Note 1 C24 Note 1
R8 51R C7 1uF C25 10nF
R9 47k C8 Note 1 C26 10nF
R10 68kΩ C9 Note 1
R11 39kΩ C10 Table 2a
C11 Table 2a
C12 Table 2a
Notes:
1. 470pF but use 47pF at 915MHz
2. 470 recommended at 450MHz
3. All inductors are Coilcraft (www.coilcraft.com)
4. 200 recommended at 160MHz

Table 2b Recommended External Components (common values)

7 PCB Layout
Careful layout of the PCB is essential for best performance. Recommended layout may be taken from evaluation kit
EV9011.

8 Application Notes
8.1 Output Power Control
The output power of the CMX901 can be controlled by varying VPARAMP from 0V to 3.3V. This in turn adjusts VGS1 and VGS2.
It is recommended to connect VGS3, along with VA (pin 14), to 3.3V dc. This gives a satisfactory power control
characteristic for TDMA systems like DMR (ETSI standards EN 300 113 and TS 102 361).

8.1.1 TDMA Operation

Careful assessment of device stability is advised during power ramping when operating into non-50Ω loads, especially at
operating frequencies of 400MHz and above.

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RF Power Amplifier CMX901

9 Packaging

Figure 17 QT8 Mechanical Outline of 28-pin WQFN (QT8)

9.1 Ordering
Order as Part No. CMX901 QT8

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RF Power Amplifier CMX901

Handling precautions: This product includes input protection, however, precautions should be taken to prevent device
damage from electro-static discharge. CML does not assume any responsibility for the use of any circuitry described. No
IPR or circuit patent licences are implied. CML reserves the right at any time without notice to change the said circuitry and
this product specification. CML has a policy of testing every product shipped using calibrated test equipment to ensure
compliance with this product specification. Specific testing of all circuit parameters is not necessarily performed.

United Kingdom tel: +44 (0) 1621 875500 email: sales@cmlmicro.com

techsupport@cmlmicro.com
Singapore tel: +65 62888129 email: sg.sales@cmlmicro.com
sg.techsupport@cmlmicro.com
United States tel: +1 336 744 5050 email: us.sales@cmlmicro.com
800 638 5577 us.techsupport@cmlmicro.com

www.cmlmicro.com

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