July 2003

7

MICRF008

MICRF008

Micrel

DO Pin

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

in Figure 4. The output is a 10

µA push-10µA pull, switched

current stage. Such an output stage is capable of driving

CMOS-type loads.

VDDBB

VSSBB

Compa-

rator

10

µA

10

µA

DO

Figure 4. DO Pin

REFOSC Pin

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

ance is quite high (200k

Ω). This is a Colpitts oscillator, with

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

standard ceramic resonators, connected from this pin to

V

tors, since these capacitors are contained inside the IC.

Externally applied signals should be AC-coupled, amplitude

limited to approximately 0.5V

age on this pin is 1.4V.

250

Ω

200k

Active

Bias

REFOSC

30pF

30pF

15

µA

VDDBB

VSSBB

VSSBB

Figure 5. REFOSC Pin

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 V

impedance to the V

to Internal

Circuits

VDDBB

VSSBB

Logic

Input

Q2

Q3

Q1

VSSBB

Figure 6. SEL0