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DA9178.001

10 Dec, 2003

TYPICAL APPLICATION (Continued)

Note 2: AGC Capacitor

The AGC and DEC capacitors must have low leakage currents due to very small 40 nA signal currents through

the capacitors. The insulation resistance of these capacitors should be higher than 70 M

Ω. Also probes with at

least 100 M

Ω impedance should be used for voltage probing of AGC and DEC pins. Electrolyte capacitors

cannot be used due to their large leakage current. Instead low leakage tantalum capacitor can be used as AGC

capacitor. DEC capacitor can be low leakage chip capacitor.

Note 3: Power Down / Fast Startup Control

Both power down and fast startup are controlled using the PDN pin. The device is in power down (turned off) if

PDN = VDD and in power up (turned on) if PDN = VSS. Fast startup is triggered by the falling edge of PDN

signal, i.e., controlling device from power down to power up. The startup time without using the fast startup

control can be several minutes but with fast startup it is shortened typically to 12 s.

Note 4: Optional Control for AGC On/Hold

AON control pin has internal pull up which turns AGC circuit on all the time if AON pin is left unconnected.

Optionally AON control can be used to hold and release AGC circuit. Stepper motor drive etc. can produce

disturbing amount of noise which can shift the input amplifier gain to unoptimal level. This can be avoided by

controlling AGC hold (AON=VSS) during stepper motor drive periods and releasing AGC (AON=VDD) when

motors are not driven.