MC34160 Datasheet, PDF (6/8 Pages) ON Semiconductor – MICROPROCESSOR VOLTAGE REGULATOR/ SUPERVISORY CIRCUIT

MC34160 MC33160
Reference
The 2.6 V bandgap reference is short circuit protected and
has a guaranteed output tolerance of ±5.0% over line, load,
and temperature. It is intended to be used in conjunction with
the Power Warning and Uncommitted comparator. The
reference can source in excess of 2.0 mA and sink a
maximum of 10 µA. For additional current sinking capability,
an external load resistor to ground must be used.
Reference biasing is internally derived from either VCC or
VO, allowing proper operation if either drops below nominal.
Chip Disable
This input is used to switch the IC into a standby mode.
When activated, internal biasing for the entire die is removed
causing all outputs to turn off. This reduces the power supply
current (ICC) to less than 0.3 mA.
Comparators
Three separate comparators are incorporated for voltage
monitoring. Their outputs can provide diagnostic information
to the microprocessor, preventing system malfunctions.
The Reset Comparator Inverting Input is internally
connected to the 2.6 V reference while the Noninverting Input
monitors VO. The Reset Output is active low when VO falls
approximately 180 mV below its regulated voltage. To
prevent erratic operation when crossing the comparator
threshold, 70 mV of hysteresis is provided.
The Power Warning Comparator is typically used to detect
an impending loss of system power. The Inverting Input is
internally connected to the reference, fixing the threshold at
2.6 V. The input power source Vin is monitored by the
Noninverting Input through the R1/R2 divider (Figure 10). This
input features an adjustable 10 µA to 50 µA current sink IH
that is programmed by the value selected for resistor RH. A
default current of 6.5 µA is provided if RH is omitted. When the
comparator input falls below 2.6 V, the current sink is
activated. This produces hysteresis if Vin is monitored
through a series resistor (R1). The comparator thresholds are
defined as follows:
Vth(lower) = Vref
1+
R1
R2
Vth(upper) = Vref
1+
R1
R2
– IIB R1
+ IH R1
The nominal hysteresis current IH equals 1.2 V/RH
(Figure 4).
The Uncommitted Comparator can be used to
synchronize the microprocessor with the ac line signal for
timing functions, or for synchronous load switching. It can
also be connected as a line loss detector as shown in
Figure 11. The comparator contains 200 mV of hysteresis
preventing erractic output behavior when crossing the input
threshold.
The Power Warning and Uncommitted Comparators each
have a transistor base–emitter connected across their inputs.
The base input normally connects to a voltage reference
while the emitter input connects to the voltage to be
monitored. The transistor limits the negative excursion on the
emitter input to – 0.7 V below the base input by supply current
from VCC. This clamp current will prevent forward biasing the
IC substrate. Zener diodes are connected to the comparator
inputs to enhance the ICs electrostatic discharge capability.
Resistors R1 and Rin must limit the input current to a
maximum of ±2.0 mA.
Each comparator output consists of an open collector NPN
transistor capable of sinking 2.0 mA with a saturation voltage
less than 0.4 V, and standing off 40 V with minimal leakage.
Internal bias for the Reset and Power Warning Comparators
is derived from either VCC or the regulator output to ensure
functionality when either is below nominal.
Heat Tab Package
The MC34160 is contained in a 16 lead plastic
dual–in–line package in which the die is mounted on a
special Heat Tab copper alloy lead frame. This tab consists of
the four center ground pins that are specifically designed to
improve thermal conduction from the die to the surrounding
air. The pictorial in Figure 8 shows a simple but effective
method of utilizing the printed circuit board medium as a heat
dissipator by soldering these tabs to an adequate area of
copper foil. This permits the use of standard board layout and
mounting practices while having the ability to more than halve
the junction to air thermal resistance. The example and graph
are for a symmetrical layout on a single sided board with one
ounce per square foot copper.
Figure 10. Typical Microprocessor Application
VCC
Vin
Cin 14
R1
Chip
Disable
15
R2
9
RH ¹⁰
+
2.6 V
Reference
Thermal
Shutdown
–
+
+
0.913 R
11
+
.01 R –
7
Reset
R
Power
16
– ^Warning
+
8
IH
IH On/Off
CO ^VO
MPU Reset
Vref
Power Warning
2.6 V
2
AC
Line
Rin
1
+
Uncommitted
Comparator
+
–
6
Line Sync.
4, 5, 12, 13
+
–
=
Sink Only
Positive True Logic
6
MOTOROLA ANALOG IC DEVICE DATA