PIC16F616-ESLASHSLSQTP datasheet(117/172 Pages) APEX

117 / 172 page

Preliminary

DS41288A-page 115

PIC16F616/16HV616

12.0

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).

12.1

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 12-1 for voltage regulator schematic.

FIGURE 12-1:

VOLTAGE REGULATOR

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 12-1.

EQUATION 12-1:

RSER LIMITING RESISTOR

12.2

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 PIC16HV616 device.

Feedback

VDD

VSS

CBYPASS

RSER

VUNREG

ISUPPLY

ISHUNT

ILOAD

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

PIC16F616-E/SLSQTP Datasheet(PDF) 117 Page - Cirrus Logic

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