MAX1479_09 Datasheet, PDF (6/10 Pages) Maxim Integrated Products – 300MHz to 450MHz Low-Power, Crystal-Based +10dBm ASK/FSK Transmitter

300MHz to 450MHz Low-Power,
Crystal-Based +10dBm ASK/FSK Transmitter
Pin Description
PIN
NAME
DESCRIPTION
1
V_DD Supply Voltage. Bypass to GND with a 10nF and 220pF capacitor as close to the pin as possible.
2
MODE
Mode Select. A logic low on MODE enables the device in ASK mode. A logic high on MODE enables the
device in FSK mode.
3
DIN
Data Input. Power amplifier is on when DIN is high in ASK mode. Frequency is high when DIN is high in
FSK mode.
4
ENABLE Standby/Power-Up Input. A logic low on ENABLE sets the device in standby mode.
5
CLKOUT Buffered Clock Output. Programmable through CLK0 and CLK1. See Table 1.
6
V_{DD_}PA
Power-Amplifier Supply Voltage. Bypass to GND with a 10nF and 220pF capacitor as close to the pin as
possible.
7
ROUT ^{Envelope-Shaping Output. ROUT controls the power-amplifier envelope rise and fall. Bypass to GND with a}
680pF and 220pF capacitor as close to the pin as possible.
8
PAOUT ^{Power-Amplifier Output. Requires a pullup inductor to the supply voltage, which can be part of the output-}
matching network to an antenna.
9
CLK0 1st Clock Divider Setting. See Table 1.
10
CLK1 2nd Clock Divider Setting. See Table 1.
11
DEV0 1st FSK Frequency-Deviation Setting. See Table 2.
12
DEV1 2nd FSK Frequency-Deviation Setting. See Table 2.
13
DEV2 3rd FSK Frequency-Deviation Setting. See Table 2.
14
XTAL1 1st Crystal Input. f_RF = 32 x f_XTAL.
15
XTAL2 2nd Crystal Input. f_RF = 32 x f_XTAL.
16
GND Ground. Connect to system ground.
—
EP
Exposed Ground Pad. EP is the power amplifier’s ground. It must be connected to PCB through a low-
inductance path.
Detailed Description
The MAX1479 is a highly integrated ASK/FSK transmit-
ter operating over the 300MHz to 450MHz frequency
band. The device requires only a few external compo-
nents to complete a transmitter solution. The MAX1479
includes a complete PLL and a highly efficient power
amplifier. The device can be set into a 0.2nA low-power
shutdown mode.
Shutdown Mode
ENABLE (pin 4) is internally pulled down with a 20µA
current source. If it is left unconnected or pulled low,
the MAX1479 goes into a low-power shutdown mode.
In this mode, the supply current drops to 0.2nA. When
ENABLE is high, the device is enabled and is ready for
transmission after 200µs (frequency settles to within
50kHz).
The 200µs turn-on time of the MAX1479 is mostly domi-
nated by the crystal oscillator startup time. Once the
oscillator is running, the 300kHz PLL bandwidth allows
fast frequency recovery during power-amplifier toggling.
Mode Selection
MODE (pin 2) sets the MAX1479 in either ASK or FSK
mode. When MODE is set low, the device operates as
an ASK transmitter. If MODE is set high, the device
operates as an FSK transmitter. In the ASK mode, the
DIN pin controls the output of the power amplifier. A
logic low on DIN turns off the PA, and a logic high turns
on the PA. In the FSK mode, a logic low on the DIN pin
is represented by the low FSK frequency, and a logic-
high input is represented by the high FSK frequency.
(The ASK carrier frequency and the lower FSK frequen-
cy are the same.) The deviation is proportional to the
crystal load impedance and pulling capacitance. The
maximum frequency deviation is 55kHz for f_RF =
315MHz and 80kHz for f_RF = 433MHz.
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