The MAX194 evaluation board generates its own high-

quality power supplies from a single DC input (8V to

20V), such as a plug-in wall transformer. When the

MAX194 evaluation board is connected to the 68HC16

µC module, the µC module uses the unregulated input

supply to generate its own separate +5V digital supply.

U6 converts the unfiltered input down to +5V to provide

the VDDA analog supply. Current spikes from the digi-

tal supply VDDD are attenuated by R1. Schottky diode

D1 protects the device substrate. U7 inverts the +12V

to -12V, and U3 regulates the -12V to -5V, providing the

VSSA analog supply.

Measuring Supply Current

To measure the supply current drawn by the MAX194,

turn off the power and prepare the board by carefully

cutting the traces at IS1, IS2, IS3, and IS4, and

installing 2-pin headers and shunts (see Table 8).

Each supply may be measured by replacing the corre-

sponding shunt with a current-meter connection. For

example, to measure the current drawn by the +5V dig-

ital supply, replace the shunt at IS4 with a current

meter. The direction of current flow is marked with

arrows on the silkscreen. Do not connect or disconnect

the current meter while the power is on.

After observing supply current in operating and shut-

down modes, the board may be restored by installing

shunts at IS1–IS4.

MAX194 Evaluation System/Evaluation Kit

8

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JUMPER

POWER SUPPLY

DESCRIPTION

IS1

VDDA

Analog +5V

IS2

VSSA

Analog -5V

IS3

VSSD

Digital -5V

IS4

VDDD

Digital +5V

Table 8. Current-Sense Jumpers