PIC16C770-I/SO Microchip Technology, PIC16C770-I/SO Datasheet - Page 115

• Manufacturer Part Number: PIC16C770-I/SO
• Description: IC MCU OTP 2KX14 A/D PWM 20-SOIC
• Manufacturer: Microchip Technology
• Series: PIC® 16Cr

Specifications of PIC16C770-I/SO

• Core Size: 8-Bit
• Program Memory Size: 3.5KB (2K x 14)
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Core Processor: PIC
• Speed: 20MHz
• Connectivity: I²C, SPI
• Number Of I /o: 15
• Program Memory Type: OTP
• Ram Size: 256 x 8
• Voltage - Supply (vcc/vdd): 4 V ~ 5.5 V
• Data Converters: A/D 6x12b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 20-SOIC (7.5mm Width)
• Controller Family/series: PIC16C
• No. Of I/o's: 16
• Ram Memory Size: 256Byte
• Cpu Speed: 20MHz
• No. Of Timers: 3
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: ISPICR1 - ADAPTER IN-CIRCUIT PROGRAMMINGAC164028 - MODULE SKT PROMATEII 20SOIC/DIP309-1013 - ADAPTER 20-SOIC TO 20-DIP309-1012 - ADAPTER 20-SOIC TO 20-DIP
• Eeprom Size: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant
• Other names: PIC16C770I/SO

11.6
11.6.1
The maximum recommended impedance for ana-
log sources is 2.5 k . This value is calculated based
on the maximum leakage current of the input pin. The
leakage current is 100 nA max., and the analog input
voltage cannot be varied by more than 1/4 LSb or
250 V due to leakage. This places a requirement on
the input impedance of 250 V/100 nA = 2.5 k .
11.6.2
For the A/D converter to meet its specified accuracy,
the charge holding capacitor (C
to fully charge to the input channel voltage level. The
analog input model is shown in Figure 11-5. The source
impedance (R
impedance directly affect the time required to charge
the capacitor C
impedance varies over the device voltage (V
Figure 11-5. The maximum recommended imped-
ance for analog sources is 2.5 k . After the analog
input channel is selected (changed) this sampling must
be done before the conversion can be started.
To calculate the minimum sampling time, Equation 11-
2 may be used. This equation assumes that 1/4 LSb
error is used (16384 steps for the A/D). The 1/4 LSb
error is the maximum error allowed for the A/D to meet
its specified resolution.
The C
A/D.
2002 Microchip Technology Inc.
HOLD
A/D Sample Requirements
RECOMMENDED SOURCE
IMPEDANCE
SAMPLING TIME CALCULATION
is assumed to be 25 pF for the 12-bit
S
) and the internal sampling switch (R
HOLD
. The sampling switch (R
HOLD
) must be allowed
DD
), see
SS
SS
)
)
EXAMPLE 11-2:
Figure 11-3 shows the calculation of the minimum time
required to charge C
the following system assumptions:
V
V
V
Solving for T
T
C
R
1/4 LSb error
V
Temp (system Max.) = 50 C
Note 1: The reference voltage (V
C
H OL D
R EF
R EF
DD
HOLD
S
PIC16C717/770/771
=
= 2.5 k
–
–
= 5V
1
C
--------------- -
16384
V
=
–
H O LD
R EF
= 25 pF
2: The charge holding capacitor (C
3: The maximum recommended impedance
--------------- -
16384
V
R E F
C
1
effect on the equation, since it cancels
itself out.
not discharged after each conversion.
for analog sources is 2.5 k . This is
required to meet the pin leakage specifi-
cation.
:
=
1k
–
R
--------------- -
16384
V
=
V
+
SS
R E F
R E F
R
V
S S
= 10 k (worst case)
R E F
HOLD
+
A/D SAMPLING TIME
EQUATION
1 e
R
–
S
1 e
. This calculation is based on
–
ln
------------------------------------------------------------------ -
C
H O LD
--------------- -
16384
------------------------------------------------------------------ -
C
H O LD
1
R
I C
DS41120B-page 113
–
T
R
+
C
I C
–
R
T
+
REF
S S
C
R
+
SS
) has no
R
+
HOLD
S
R
S
) is