CC2400 Chipcon AS, CC2400 Datasheet - Page 16

• Manufacturer Part Number: CC2400
• Description: 2.4 GHz RF Transceiver
• Manufacturer: Chipcon AS

Application Circuit
Few external components are required for
the
application circuit is shown in Figure 3. A
description of the external components
referring to Figure 3 are described in
Table 1. The bill of materials (BOM) is
given in Table 2.
Input / output matching
The RF input/output is high impedance
and differential (optionally one output can
be disabled for single-ended operation).
The optimum differential load for the RF
port is 115+j180 Ω.
When using an unbalanced antenna like a
monopole, a balun should be used in
order to get optimum performance. The
balun can be implemented using low-cost
discrete inductors and capacitors. The
balun consists of C61, C62, C71, C81,
L61, L62 and L72, and will match the RF
input/output to 50 Ω, see Figure 3. L61
and L62 also provide DC biasing of the
LNA/PA input/output. L71 is used to
isolate
internal T/R switch circuit is used to switch
between the LNA and the PA. See
“Input/output matching” on page 48 for
more details.
If a balanced antenna, like a folded dipole,
is used, the balun can be omitted. If the
antenna also provides a DC path from
TXRX_SWITCH pin to the RF pins,
inductors are not needed for DC bias. The
Chipcon AS
Table 1. Overview and description of external components for an unbalanced antenna
operation
Ref
C71
C61
C81
C62
C421
C431
L61
L62
L71
L81
R451
XTAL
the
SmartRF
TXRX_SWITCH
of
(balun implemented with low cost discrete components)
®
CC2400
CC2400 PRELIMINARY Datasheet (rev. 1.1), 2003-10-02
.
Description
Front-end bias decoupling and match, see page 48
Discrete balun and match, see page 48
Discrete balun and match, see page 48
DC block to antenna and match
16MHz crystal load capacitor, see page 47
16MHz crystal load capacitor, see page 47
DC bias and match, see page 48
DC bias and match, see page 48
RF blocking inductor, see page 48
Discrete balun and match, see page 48
Precision resistor for current reference generator
16MHz crystal, see page 47
A
pin.
typical
An
SmartRF
L71 isolation inductor should still be used.
Figure 4 shows a typical application circuit
with differential antenna. The dipole has a
virtual
provided without degradation in antenna
performance.
Bias resistor
The bias resistor R451 is used to set an
accurate bias current.
Crystal
An external crystal with two loading
capacitors (C421 and C431) is used for
the crystal oscillator. See page 47 for
details.
Digital I/O
The supply voltage for the digital I/O must
match the interfacing circuit. The digital
I/Os
microcontrollers with supply voltages in
the range 1.6 – 3.6 V.
Power supply decoupling and filtering
Proper power supply decoupling must be
used for optimum performance. The
placement and size of the decoupling
capacitors and the power supply filtering
are very important to achieve the best
performance in an application. Chipcon
provides a compact reference design that
should be followed very closely.
ground
of
CC2400
point,
®
CC2400
hence
can
Page 16 of 73
interface
bias
is