MAX2430 Ver la hoja de datos (PDF) - Maxim Integrated
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MAX2430 Datasheet PDF : 10 Pages
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Low-Voltage, Silicon RF Power
Amplifier/Predriver
VCC
1nF
ON
OFF
SHDN
RF INPUT
GND1
CIN
1nF
RFIN
VCC1
MASTER
BIAS
GAIN
50Ω
GND2
2.2nF
L2*
VCC2 BIAS
OUTPUT
5nH
BIAS
MAX2430
DRIVER
GND3
˜15Ω
GND4
* L2 = 8nH FOR NARROW SO PACKAGE (MAX2430ISE)
L2 = 12nH FOR PwrQSOP PACKAGE (MAX2430IEE)
Figure 1. Typical Application Circuit
VCC
1nF
LC
RC
47nH
470Ω
9
RFOUT
L1
8nH CO
CSH
THREE-ELEMENT
MATCHING NETWORK
RF OUTPUT
RL
˜50Ω
CO AND CSH TUNED FOR MAXIMUM POWER OUTPUT AT THE
DESIRED FREQUENCY BETWEEN 800MHz AND 1000MHz.
MAX2430IEE (PwrQSOP) UNDERSIDE METAL SLUG MUST
BE SOLDERED TO PCB GROUND PLANE.
__________Applications Information
Output Matching
The optimum internal load impedance seen by RFOUT
is approximately 15Ω. This on-chip low drive imped-
ance provides maximum power transfer and best effi-
ciency under low (3V) supply conditions where the
voltage-swing headroom is limited. For example, driv-
ing an output power of 21.3dBm (135mW) into 50Ω
translates to a 7.35Vp-p swing at the output. An RF
amplifier would require at least a 4.5V supply to drive a
50Ω load directly. However, driving 21.3dBm into 15Ω
translates to 4.02Vp-p. The MAX2430 can achieve a
voltage swing of 4.02Vp-p or 2.01Vp from a 3V supply
voltage without saturating the output transistor.
Figure 1 shows the MAX2430 configured for 800MHz to
1000MHz operation. The output matching circuitry con-
verts the desired 50Ω load impedance to the 15Ω opti-
mal load seen by the output transistor’s collector. This
configuration uses a low-loss, controlled-Q inductor net-
work. Starting from the RFOUT pin, this network consists
of a series L (which includes the 5nH package parasitic
inductance), series C, and shunt C. The design equa-
tions for this network are as follows:
R1 = Output resistance as seen by the
collector ~15Ω
RL = Desired load resistance
The controlled-Q inductor network requires that
( ) RL > R1 and Q > RL / R1 − 1 . Choose Q and com-
pute matching components as given below:
Let
( ) A = RL x R1 − R12
XL = Q x R1
XCo = XL − A
XCsh = RL x R1 / A
L1 = XL / ω - 5nH of package
inductance
CO
=
1
ωX Co
C SH
=
1
ωX Csh
where ω equals the center frequency in radians/second.
Recommended starting values for L1 and L2 are given
in Table 1.
Table 1. Recommended L1 and L2 Starting
Values
f = ω / 2π
(MHz)
400 to 600*
600 to 800*
800 to 1000
L1(nH)
22
15
8
MAX2430ISE MAX2430IEE
L2(nH)
L2(nH)
12
18
8
12
8
12
*Not characterized
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