AME8550 Datasheet, PDF (14/21 Pages) Analog Microelectronics – Voltage Detector

AME, Inc.
AME8550
n Notes on Use
1. When a resistor is connected between the V_DD pin and
the input with CMOS output configurations, oscillation
may occur as a result of voltage drops at R if load cur-
IN
rent (I_OUT) exists. ( refer to 5 - (1) below )
2. When a resistor is connected between the V_DD pin and
the input with CMOS output configurations, irrespective
of Nch output configurations, oscillation may occur as a
result of through current at the time of voltage release
even if load current (I_OUT) does not exist.( refer to 5 - (1)(2)
below )
3. With a resistor connected between the V_DDpin and the
input, detect and release voltage will rise as a result of
the IC’s supply current flowing through the V pin.
DD
4. In order to stabilise the IC’s operations, please en-
sure that V pin’s input frequency’s rise and fall times
DD
are more than several µ sec / V.
5. Oscillation
(1) Output current oscillation with the CMOS output
configuration
When the voltage applied at IN rises, release op-
erations commence and the detector’s output volt-
age increases. Load current (I ) will flow at R .
OUT
L
Because a voltage drop ( R_IN x I_OUT) is produced at
the R_IN resistor, located between the input (IN) and
the V_DD pin, the load current will flow via the IC’s
V_DD pin. The voltage drop will also lead to a fall in
the voltage level at the V pin. When the V pin
DD
DD
voltage level falls below the detect voltage level,
detect operations will commence. Following detect
operations, load current flow will cease and since
voltage drop at R_IN will disappear, the voltage level
at the V_DD pin will rise and release operations will
begin over again.
Oscillation may occur with this “ release - de-
tect - release “ repetition.
Further, this condition will also appear via means
of a similar mechanism during detect operations.
Voltage Detector
(2) Oscillation as a result of through current
Since the AME8550 series are CMOS ICS,
through current will flow when the IC’s internal cir-
cuit switching operates(during release and detect
operations ).Consequently, oscillation is liable to
occur as a result of drops in voltage at the through
current’s resistor (R ) during release voltage op-
IN
erations. ( refer to diagram 2 )
Since hysteresis exists during detect operations,
oscillation is unlikely to occur.
Input
R_IN
R_INxI_OUT
voltage drop
AME8550
I_OUT
V_DD
V_OUT
V_SS
Diagram1
Input
R_IN
R_INxI_SS*
voltage drop
AME8550
V_DD
V_OUT
V_SS
Iss*
(includes through
current)
Diagram2
14