tda9870ah NXP Semiconductors, tda9870ah Datasheet - Page 12

• Manufacturer Part Number: tda9870ah
• Description: Digital Tv Sound Processor Dtvsp
• Manufacturer: NXP Semiconductors

Philips Semiconductors
6.1.9
The reset is active LOW. In order to perform a reset at
power-up, a simple RC circuit may be used which consists
of the integrated passive pull-up resistor and an external
capacitor connected to ground. The pull-up resistor has a
nominal value of 50 k , which can easily be measured
between pins CRESET and V
voltage has reached a certain minimum, the state of the
circuit is completely undefined, and it remains in this
undefined state unless a reset is applied.
The reset is guaranteed to be active when:
The required capacitor value depends on the gradient of
the rising power supply voltage. The time constant of the
RC circuit should be clearly larger than the rise time of the
power supply, to make sure that the reset condition is
always satisfied (see Fig.4), even considering the
tolerance spread. To avoid problems with a too slow
discharging of the capacitor at power-down, it may be
helpful to add a diode from pin CRESET to V
be noted that the internal ESD protection diode does not
help here as it only conducts at higher voltages. Under
difficult power supply conditions (e.g. very slow or
non-monotonic ramp-up), it is recommended to drive the
reset line from a microcontroller port or the like.
1999 Dec 20
The power supply is within the specified limits
(4.75 and 5.5 V)
The crystal oscillator is functioning
The voltage at pin CRESET is below 0.3V
V
Digital TV Sound Processor (DTVSP)
DDD
= 5.0 V, typically below 1.8 V).
P
OWER
-
ON RESET
DDD2
. Before the supply
DDD
DDD
. It should
(1.5 V if
12
handbook, halfpage
voltage
(V)
1.5
5
Fig.4 Reset at power-on.
V DDD
4.75 V
reset active
guaranteed
V CRESET
Product specification
TDA9870A
0.3V DDD
MHB595
t