Datasheet

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SLES102A – DECEMBER 2003 – REVISED NOVEMBER 2006
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14
Power-On and External Reset Functions
The PCM1798 includes a power-on reset function. Figure 19 shows the operation of this function. With V
DD
> 2 V,
the power-on reset function is enabled. The initialization sequence requires 1024 system clocks from the time
V
DD
> 2 V.
The PCM1798 also includes an external reset capability using the RST input (pin 14). This allows an external
controller or master reset circuit to force the PCM1798 to initialize to its default reset state.
Figure 20 shows the external reset operation and timing. The RST pin is set to logic 0 for a minimum of 20 ns. The
RST pin is then set to a logic 1 state, thus starting the initialization sequence, which requires 1024 system clock
periods. The external reset is especially useful in applications where there is a delay between the PCM1798 power
up and system clock activation.
Reset Reset Removal
1024 System Clocks
V
DD
2.4 V (Max)
2 V (Typ)
1.6 V (Min)
Internal Reset
System Clock
Figure 19. Power-On Reset Timing
Reset Reset Removal
1024 System Clocks
Internal Reset
System Clock
RST (Pin 14)
t
(RST)
1.4 V
PARAMETERS MIN MAX UNITS
t
(RST)
Reset pulse duration, LOW 20 ns
Figure 20. External Reset Timing