Datasheet

 2010 Microchip Technology Inc. DS39905E-page 25
PIC24FJ256GA110 FAMILY
2.4 Voltage Regulator Pins
(ENVREG/DISVREG and
V
CAP/VDDCORE)
The on-chip voltage regulator enable/disable pin
(ENVREG or DISVREG, depending on the device
family) must always be connected directly to either a
supply voltage or to ground. The particular connection
is determined by whether or not the regulator is to be
used:
• For ENVREG, tie to V
DD to enable the regulator,
or to ground to disable the regulator
• For DISVREG, tie to ground to enable the
regulator or to V
DD to disable the regulator
Refer to Section 25.2 “On-Chip Voltage Regulator”
for details on connecting and using the on-chip
regulator.
When the regulator is enabled, a low-ESR (< 5Ω)
capacitor is required on the V
CAP/VDDCORE pin to
stabilize the voltage regulator output voltage. The
VCAP/VDDCORE pin must not be connected to VDD and
must use a capacitor of 10 µF connected to ground. The
type can be ceramic or tantalum. Suitable examples of
capacitors are shown in Ta ble 2- 1 . Capacitors with
equivalent specification can be used.
Designers may use Figure 2-3 to evaluate ESR
equivalence of candidate devices.
The placement of this capacitor should be close to
V
CAP/VDDCORE. It is recommended that the trace
length not exceed 0.25 inch (6 mm). Refer to
Section 28.0 “Electrical Characteristics” for
additional information.
When the regulator is disabled, the V
CAP/VDDCORE pin
must be tied to a voltage supply at the V
DDCORE level.
Refer to Section 28.0 “Electrical Characteristics” for
information on VDD and VDDCORE.
FIGURE 2-3: FREQUENCY vs. ESR
PERFORMANCE FOR
SUGGESTED V
CAP
.
Note: This section applies only to PIC24F J
devices with an on-chip voltage regulator.
10
1
0.1
0.01
0.001
0.01 0.1 1 10 100 1000 10,000
Frequency (MHz)
ESR ()
Note: Typical data measurement at 25°C, 0V DC bias.
TABLE 2-1: SUITABLE CAPACITOR EQUIVALENTS
Make Part #
Nominal
Capacitance
Base Tolerance Rated Voltage Temp. Range
TDK C3216X7R1C106K 10 µF ±10% 16V -55 to 125ºC
TDK C3216X5R1C106K 10 µF ±10% 16V -55 to 85ºC
Panasonic ECJ-3YX1C106K 10 µF ±10% 16V -55 to 125ºC
Panasonic ECJ-4YB1C106K 10 µF ±10% 16V -55 to 85ºC
Murata GRM32DR71C106KA01L 10 µF ±10% 16V -55 to 125ºC
Murata GRM31CR61C106KC31L 10 µF ±10% 16V -55 to 85ºC