PIC16HV785 Microchip Technology Inc., PIC16HV785 Datasheet - Page 128

• Manufacturer Part Number: PIC16HV785
• Description: 20-pin Flash-based 8-bit Cmos Microcontroller
• Manufacturer: Microchip Technology Inc.

PIC16F785/HV785
16.0
The PIC16HV785 includes a permanent internal 5 volt
(nominal) shunt regulator in parallel with the V
This eliminates the need for an external voltage regula-
tor in systems sourced by an unregulated supply. All
external devices connected directly to the V
share the regulated supply voltage and contribute to
the total V
16.1
The regulator operates by maintaining a constant
voltage at the V
current in response to variations of the V
and the unregulated supply voltage. The regulator
behaves like a fully compensated Zener diode. (See
Figure 16-1).
FIGURE 16-1:
DS41249D-page 126
VOLTAGE REGULATOR
Regulator Operation
DD
V
supply current (I
DD
DD
V
UNREG
pin by adjusting the regulator shunt
R
REGULATOR
SER
To other circuitry
PIC16HV785
Voltage
Regulator
LOAD
).
DD
supply load
DD
DD
pin will
pin.
Preliminary
An external current limiting resistor, R
between the unregulated supply, V
pin, drops the difference in voltage between V
and V
defined by Equation 16-1.
EQUATION 16-1:
16.2
The total V
46 mA so that it falls within the voltage regulator shunt
current dynamic range. If the load current rises above
the expected maximum, the regulator will be starved for
current and go out of regulation causing V
Since the regulator uses the band gap voltage as the
regulated voltage reference, the VR voltage reference
is permanently enabled in the PIC16HV785 device.
Where:
R
R
VU
VU
V
I
1.05
0.95
LOAD
DD
MAX
MIN
MIN
MAX
DD
R
R
. R
MAX
Regulator Precautions
MIN
= maximum value of R
= minimum value of R
= minimum value of V
= maximum value of V
= regulated voltage (5V nominal)
= maximum expected load current in mA
= compensation for +5% tolerance of R
= compensation for -5% tolerance of R
DD
SER
including I/O pin currents and external
circuits connected to V
=
=
load current variation must be less than
must be between R
(VU
(VU
1.05 • (4
R
MIN
MIN
© 2006 Microchip Technology Inc.
0.95 • (50
SER
- V
- V
M
LIMITING RESISTOR
A + I
DD
DD
UNREG
SER
UNREG
) • 1000
) • 1000
SER
M
UNREG
LOAD
DD
A)
(ohms)
MAX
(ohms)
.
)
, and the V
SER
and R
DD
, located
to drop.
UNREG
MIN
SER
SER
DD
as