MAX7058ATG データシートの表示（PDF） - Maxim Integrated

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MAX7058ATG

315MHz/390MHz Dual-Frequency ASK Transmitter

Maxim Integrated 

MAX7058

315MHz/390MHz Dual-Frequency ASK Transmitter

Detailed Description

The MAX7058 alternately transmits OOK/ASK data at

315MHz or 390MHz using a single crystal. The device

has integrated tuning capacitors at the output of the power

amplifier to ensure high efficiency at each frequency.

The crystal-based architecture of the MAX7058 eliminates

many of the common problems with surface acoustic

wave (SAW) transmitters, by providing greater modulation

depth, faster frequency settling, tighter transmit frequen-

cy tolerance, and reduced temperature dependence. In

particular, the tighter transmit frequency tolerance means

that a super-heterodyne receiver with a narrower IF band-

width (therefore lower noise bandwidth) can be used. The

payoff is improved overall receiver performance when

using a super-heterodyne receiver such as the MAX1471,

MAX1473, MAX7033, MAX7034, or MAX7042.

Dual Frequency

The MAX7058 is a crystal-referenced PLL VHF/UHF

transmitter that transmits OOK/ASK data at 315MHz or

390MHz. Two fixed synthesizer-divide ratios of 21 and 26

can be selected, and a 15MHz crystal is used as the ref-

erence for 315MHz/390MHz operation. The FSEL pin is

used to select the divide ratio. The MAX7058 can operate

over a 300MHz to 450MHz range by using different crys-

tal frequencies. The two operating frequencies are always

related by a 26:21 ratio.

An internal variable shunt capacitor is connected at the

PA output. This capacitor is controlled by four external

logic bits (CAP1–CAP4) to maintain highly efficient

transmission at either 315MHz or 390MHz. This means

that it is possible to change the frequency and retune

the antenna to the new frequency in a very short time.

The combination of rapid-antenna tuning ability with

rapid-synthesizer tuning makes the MAX7058 a true fre-

quency-agile transmitter. The tuning capacitor has a

resolution of 0.5pF. When the MAX7058 operates at

315MHz, the capacitance added at PAOUT corresponds

to the setting at CAP1–CAP4, as seen in Table 2. When

the MAX7058 operates at 390MHz, the MAX7058 does

not add any internal shunt capacitance at PAOUT.

The MAX7058 supports ASK data rates up to 100kbps

NRZ and features adjustable output power through an

external resistor to more than +10dBm into a 50Ω load.

Power-Up and Standby Modes

The MAX7058 can be placed in either an enabled state

(all circuit blocks necessary for transmission powered

up) or a disabled state (low-current standby). The state

selection can be controlled either by ENABLE (ENABLE

method) or by activity on DIN (auto-power-up method).

In either method, the MAX7058 can begin transmission

within 250µs after being enabled. Either method can be

used with any TOGGLE/FSEL operating mode.

In the ENABLE method, setting ENABLE to a log-

ic-high state enables the MAX7058 and setting it to a

logic-low state disables the MAX7058. To avoid conflict

with the auto-power-up method, DIN must be set to a

logic-low state before ENABLE is set to a logic-low state,

and remains low until after ENABLE is set to a logic-

high state.

In the auto-power-up method, ENABLE can be hard-wired

to a logic-low state and a rising edge on DIN will enable

the MAX7058. The MAX7058 will remain enabled until

DIN is placed in a steady logic-low state for 222 cycles of

the reference clock (279.62ms with a 15MHz crystal), at

which time the MAX7058 will be disabled.

When the MAX7058 is enabled, the active pulldowns

at CAP1–CAP4, FSEL, and TOGGLE will be turned on.

When the MAX7058 is disabled, these active pulldowns

will be turned off. The active pulldowns at ENABLE and

DIN are always turned on.

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