MICRF008 Просмотр технического описания (PDF) - Micrel

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MICRF008

QwikRadio™ Sweep-Mode Receiver

Micrel 

MICRF008

DO Pin

The output stage for the Data Comparator (DO pin) is shown

in Figure 4. The output is a 10µA push-10µA pull, switched

current stage. Such an output stage is capable of driving

CMOS-type loads.

Compa-

rator

VDDBB

10µA

DO

10µA

VSSBB

Figure 4. DO Pin

REFOSC Pin

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

ance is quite high (200kΩ). This is a Colpitts oscillator, with

internal 30pF capacitors. This input is intended to work with

standard ceramic resonators, connected from this pin to

VSSBB. The resonators should not contain integral capaci-

tors, since these capacitors are contained inside the IC.

Externally applied signals should be AC-coupled, amplitude

limited to approximately 0.5VPP. The nominal DC bias volt-

age on this pin is 1.4V.

Micrel

Control Input (SEL0)

Control input circuitry is shown in Figure 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”

pullup to VDDBB. Typical pullup current is 5µA, leading to an

impedance to the VDDBB supply of typically 1MΩ.

VDDBB

Q1

VSSBB

Logic

Input

Q2

to Internal

Circuits

Q3

VSSBB

Figure 6. SEL0

REFOSC

30pF

Active

Bias

VDDBB

200k

250Ω

30pF

15µA

VSSBB

VSSBB

Figure 5. REFOSC Pin

July 2003

7

MICRF008

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