MICRF005BM データシートの表示（PDF） - Micrel

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MICRF005BM

115kbps, 800MHz - 1GHz UHF Receiver

Micrel 

MICRF005

DO Pin

Compa-

rator

VDDBB

80µA

DO

Micrel

pullup to VDDBB. Typical pullup current is 8.5µA, leading to an

impedance to the VDDBB supply of typically 1MΩ.

T/R Pin

VDDBB

Q1

80µA

VSSBB

Figure 4. DO Pin

The output stage for DO (digital output) is shown in Figure 4.

The output is a 90µA push and 90µA pull switched-current

stage. This output stage is capable of driving CMOS loads.

An external buffer-driver is recommended for driving high-

capacitance loads.

REFOSC Pin

Active

Bias

VDDBB

REFOSC

200k

15pF

250Ω

7.5pF

30µA

VSSBB

VSSBB

Figure 5. REFOSC Pin

The REFOSC input circuit is shown in Figure 5. Input imped-

ance is high (300kΩ). This is a Colpitts oscillator with internal

capacitors. The nominal dc bias voltage on this pin is 1.4V.

SHUT Pin

VDDBB

Q2

VDDBB Q3

VSSBB

Figure 7. T/R Pin

The transmit/receive function is controlled by the logic state

of T/R. T/R is internally tied to VSS. When T/R is open circuit

or in the low state, the MICRF005 functions in its normal

receive operating mode. The T/R pin may be pulled high to

Vdd, this will place the receiver in a “stand-by” operating

mode. This mode is intended for use during transmit cycles

in transceiver applications where the receiver is co-located

with a transmitter. In this “transmit” mode, the receiver

oscillator remains active but the AGC function is disabled and

the CAGC pin is tri-stated to hold the AGC capacitor voltage.

This function enables the MICRF005 to quickly resume

receive operation after a transmit cycle.

Q1

VSSBB

SHUT

Q2

to Internal

Circuits

Q3

VSSBB

Figure 6. SHUT Pin

Control input circuitry is shown in Figures 6. The standard

input is a logic inverter constructed with minimum geometry

MOSFETs (Q2, Q3). P-channel MOSFET Q1 is a large

channel length device which functions essentially as a “weak”

October 2001

7

MICRF005

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