CS8151YTHA7 ,5V, 100mA Low Dropout Linear Regulator with WATCHDOG, RESETbar, & WAKE UP
CS8151YTVA7 ,5V, 100mA Low Dropout Linear Regulator with WATCHDOG, RESETbar, & WAKE UPThe CS8151 is a precision 5.0 V, 100 mA micro−power voltageregulator with very low quiescent curren ..
CS-8156 ,12 V, 5.0 V Low Dropout Dual Regulator with ENABLEBlock Diagramwill take the output voltage to reach its nominal value.Conversely, if the capacitor i ..
CS8156YTHA5 ,12 V, 5.0 V Low Dropout Dual Regulator with ENABLE3SR003AN/DMost aluminum capacitors are unsuitable for applicationswhere they will be exposed to tem ..
CS8156YTVA5 ,12 V, 5.0 V Low Dropout Dual Regulator with ENABLEblock diagram of a low drop linear regulatorsimply use the one shown in the application diagram of ..
CS8182 ,Micropower 200mA Low Dropout Tracking Regulator/Line DriverFeaturesGND GNDAdjV /ENABLEREF• 200 mA Source Capability• Output Tracks within ±10 mV Worst CaseTab ..
CXD1818R , CD-ROM Decoder
CXD1818R , CD-ROM Decoder
CXD1856Q , MPEG1 Decoder
CXD1856Q , MPEG1 Decoder
CXD1856Q , MPEG1 Decoder
CXD1856Q , MPEG1 Decoder
CS8151YDWF16-CS8151YTHA7
5V, 300mA Linear Regulator with RESETbar and ENABLEbar
SR002AN/D
Linear Regulators
with Microprocessor
Control Functions
Kieran O’Malley
ON Semiconductor
2000 South County Trail
East Greenwich, RI 02818Although microprocessors are often considered the “brains” of a control system, they need a well regulated power supply and
constant supervision for consistent operation. The system designer must choose between building these supervisory functions
using discrete circuitry, a microprocessor supervisory IC, or a regulator which has the supervisory functions included. This article
examines each of the common supervisory functions required in a microprocessor control system and shows how they are
integrated into a SMART REGULATOR to provide a complete system solution.
IntroductionON Semiconductor SMART REGULATORs are linear
regulators that provide a power supply and supervisory
functions for microprocessor control systems. Along with
the basic 5.0 V or 3.3 V supply, a microprocessor also
requires circuitry to provide functions such as: Power on Reset Low Voltage Reset Watchdog Timer Wake–up Timer On–Off control or Enable
Several of the newer microprocessors have some of these
functions already incorporated but most designers prefer
that supervisory tasks are handled by an external device to
provide an additional safety measure. (A microprocessor
will not be able to detect its own errors, especially in low
supply voltage situations.)
Microprocessor control functions can be implemented
with individual discrete circuits, microprocessor supervisor
IC’s, or by using a SMART REGULA TOR like those
manufactured by ON Semiconductor . The advantage that a
SMART REGULATOR offers is complete integration
where all the functions are fully compatible with each other
in a single space saving design.
Power On ResetWhen power is initially applied to a microprocessor, its
internal registers contain random data. Applying a Reset to
the microprocessor overcomes the potential for errors by
resetting all internal circuitry to a predictable starting point.
To ensure proper startup, the reset input of the
microprocessor must be held low for a fixed amount of time.
During this time the supply voltage reaches its nominal
value and the oscillator frequency stabilizes. This power on
reset period is usually specified by the microprocessor
manufacturer as a number of clock cycles or a time period.
The time period ranges from 20 to several hundred
milliseconds depending on the microprocessor.
Reset circuitry is powered either directly from the
regulator’s input voltage, VIN or from its output voltage,
VOUT. If the reset circuitry is powered from VIN, the Reset
will not function when the
suddenly or drops out of regulation. However, the
microprocessor may continue to work, powered by the
output capacitor voltage. Without a valid Reset, the
microprocessor may operate erroneously.
Because
SMART REGULATOR reset circuitry is powered from the
regulator’s output voltage, VOUT, rather than its input
voltage, VIN. Reset will function for values of VOUT as low
as 1.0 Volt.
Delayed ResetON Semiconductor SMART REGULATORs have either
a delayed Reset or a real time Reset. In a delayed reset circuit
like the one in the CS8126, the user programs the time for
which the reset output remains low with an external
capacitor, CDELAY. The CS8126 uses an internal current
source to charge CDELAY when the output voltage is above
a predetermined level (VRT(ON)) as shown in Figure 1. The
reset output is an open collector NPN transistor that requires
a pull up resistor (Figure 2, RRST) connected to VOUT.
The reset delay time is calculated from the formula:
DelayTime
Using an ideal 0.1 μF capacitor, the delay time ranges
from 22 ms to 65 ms due to regulator variation alone.
