ncv8769 ON Semiconductor, ncv8769 Datasheet - Page 12

• Manufacturer Part Number: ncv8769
• Description: Ultra Low Iq 150 Ma Ldo Regulator With Reset And Early Warning
• Manufacturer: ON Semiconductor

thermal shutdown and internal current limit. Typical
characteristics are shown in Figures 4 to 22.
Input Decoupling (C
and should be connected close to the NCV8769 package.
Higher capacitance and lower ESR will improve the overall
line and load transient response.
appropriate input filter must be used in order to decrease
rising and/or falling edges below 50 V/ms for proper
operation. The filter can be composed of several capacitors
in parallel.
Output Decoupling (C
a minimum Equivalent Series Resistance (ESR) for the
output capacitor. Stability region of ESR vs. Output Current
is shown in Figure 13. The minimum output decoupling
value is 1 mF and can be augmented to fulfill stringent load
transient requirements. The regulator works with ceramic
chip capacitors as well as tantalum devices. Larger values
improve noise rejection and load transient response.
Reset Delay Time Select
DT pin determines the available Reset Delay times. The part
is designed for use with DT tied to ground or OUT, but may
be controlled by any logic signal which provides a threshold
between 0.8 V and 2 V. The default condition for an open DT
pin is the slower Reset time (DT = GND condition). Times
are in pairs and are highlighted in the chart below. Consult
factory for availability. The Delay Time select (DT) pin is
logic level controlled and provides Reset Delay time per the
chart. Note the DT pin is sampled only when RO is low, and
changes to the DT pin when RO is high will not effect the
reset delay time.
Reset Operation
provide feedback to the microprocessor of an out of
regulation condition. The timing diagram of reset function
is shown in Figure 21. This is in the form of a logic signal on
RO. Output voltage conditions below the RESET threshold
cause RO to go low. The RO integrity is maintained down
to V
internal pull−up connected to the output (V
pull−up is necessary.
decreases below its minimum operating limit.
The NCV8769 regulator is self−protected with internal
A ceramic or tantalum 0.1 mF capacitor is recommended
If extremely fast input voltage transients are expected then
The NCV8769 is a stable component and does not require
Selection of the NCV8769yz devices and the state of the
A reset signal is provided on the Reset Output (RO) pin to
Reset signal is also generated in case when input voltage
out
= 1.0 V. The Reset Output (RO) circuitry includes
in
)
out
)
out
APPLICATIONS INFORMATION
) No external
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12
NOTE:
Sense Input (SI)/Sense Output (SO) Voltage Monitor
warning to the microprocessor of a possible reset signal. The
reset signal typically turns the microprocessor off
instantaneously. This can cause unpredictable results with
the microprocessor. The signal received from the SO pin will
allow the microprocessor time (T
present task before shutting down. This function is
performed by a comparator referenced to the band gap
voltage. The actual trip point can be programmed externally
using a resistor divider to the input monitor (SI). (See
Figure 1) The values for R
typical threshold of 1.2 V on the SI pin according to
Equations 1 and 2, where V
input voltage at which Early Warning signal has to be
generated. R
100 kW to 1 MW. The higher are values of resistors R
R
divider, however this also increases a delay between Input
voltage and SI input voltage caused by charging SI input
capacitance with higher RC constant. The delay can be
lowered by decreasing the resistors values with consequence
of resistor divider current is increased.
Sense Output
internal 30 kW pull up resistor to V
SO Monitor timing waveforms as a result of the circuit
depicted in Figure 1. If the input voltage decreases the
output voltage decreases as well. If the SI input low
threshold voltage is crossed it causes the voltage on the SO
output goes low sending a warning signal to the
microprocessor that a reset signal may occur in a short
period of time. T
to complete the function it is currently working on and get
ready for the reset shutdown signal.
RESET DELAY AND RESET THRESHOLD OPTIONS
SI2
Part Number
The Sense Output is from an open drain driver with an
NCV87695z
An on-chip comparator is available to provide early
the lower is current flowing through the resistor
The timing values can be selected from following list: 8, 16,
32, 64, 128 ms. The reset threshold values can be selected
from the following list: 90% and 93%. Contact factory for
other timing combinations not included in the table.
SI2
R
V
is recommended to be selected in range of
WARNING
SI1
in_EW(th)
Reset Time
DT = GND
+ R
16 ms
SI2
+ 1.25 1 )
is the time the microprocessor has
SI1
in_EW(th)
V
in_EW(th)
and R
1.2
Reset Time
WARNING
DT = V
out
32 ms
is demanded value of
SI2
R
R
. Figure 23 shows the
* 1
SI1
SI2
out
are selected for a
) to complete its
Threshold
Reset
93%
SI1
(eq. 1)
(eq. 2)
and