PIC16F610 Datasheet, PDF (107/180 Pages) Microchip Technology – 14-Pin, Flash-Based 8-Bit CMOS Microcontrollers

PIC16F610/616/16HV610/616
11.0 VOLTAGE REGULATOR
The PIC16HV616 includes a permanent internal 5 volt
(nominal) shunt regulator in parallel with the VDD pin.
This eliminates the need for an external voltage
regulator in systems sourced by an unregulated supply.
All external devices connected directly to the VDD pin
will share the regulated supply voltage and contribute
to the total VDD supply current (ILOAD).
11.1 Regulator Operation
A shunt regulator generates a specific supply voltage
by creating a voltage drop across a pass resistor RSER.
The voltage at the VDD pin of the microcontroller is
monitored and compared to an internal voltage refer-
ence. The current through the resistor is then adjusted,
based on the result of the comparison, to produce a
voltage drop equal to the difference between the supply
voltage VUNREG and the VDD of the microcontroller.
See Figure 11-1 for voltage regulator schematic.
FIGURE 11-1:
VOLTAGE REGULATOR
VUNREG
ISUPPLY
RSER
CBYPASS
ISHUNT
ILOAD
VDD
Feedback
VSS
An external current limiting resistor, RSER, located
between the unregulated supply, VUNREG, and the VDD
pin, drops the difference in voltage between VUNREG
and VDD. RSER must be between RMAX and RMIN as
defined by Equation 11-1.
EQUATION 11-1: RSER LIMITING RESISTOR
RMAX =
(VUMIN - 5V)
1.05 • (4 MA + ILOAD)
RMIN =
(VUMAX - 5V)
0.95 • (50 MA)
Where:
RMAX = maximum value of RSER (ohms)
RMIN = minimum value of RSER (ohms)
VUMIN = minimum value of VUNREG
VUMAX = maximum value of VUNREG
VDD = regulated voltage (5V nominal)
ILOAD = maximum expected load current in mA
including I/O pin currents and external
circuits connected to VDD.
1.05 = compensation for +5% tolerance of RSER
0.95 = compensation for -5% tolerance of RSER
11.2 Regulator Considerations
The supply voltage VUNREG and load current are not
constant. Therefore, the current range of the regulator
is limited. Selecting a value for RSER must take these
three factors into consideration.
Since the regulator uses the band gap voltage as the
regulated voltage reference, this voltage reference is
permanently enabled in the PIC16F610/16HV610
devices.
© 2007 Microchip Technology Inc.
Preliminary
DS41288C-page 105