PIC16F946T-I/PT Microchip Technology, PIC16F946T-I/PT Datasheet - Page 157

• Manufacturer Part Number: PIC16F946T-I/PT
• Description: Microcontroller
• Manufacturer: Microchip Technology
• Series: PIC® 16Fr

Specifications of PIC16F946T-I/PT

• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, LCD, POR, PWM, WDT
• Number Of I /o: 53
• Program Memory Size: 14KB (8K x 14)
• Program Memory Type: FLASH
• Eeprom Size: 256 x 8
• Ram Size: 336 x 8
• Voltage - Supply (vcc/vdd): 2 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 64-TFQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: MA160011 - DAUGHTER BOARD PICDEM LCD 16F91X
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

12.2
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 12-4. The
source impedance (R
switch (R
required to charge the capacitor C
switch (R
(V
mended impedance for analog sources is 10 k .
EQUATION 12-1:
© 2005 Microchip Technology Inc.
DD
Where C
Solving for T
Therefore:
Note 1: The reference voltage (V
), see Figure 12-4. The maximum recom-
T
2: The charge holding capacitor (C
3: The maximum recommended impedance for analog sources is 10 k . This is required to meet the pin
A/D Acquisition Requirements
SS
T
ACQ
SS
ACQ
V
V
V
HOLD
) impedance varies over the device voltage
T
leakage specification.
) impedance directly affect the time
AP P LIED
AP P LIED
AP P LIED
C
C
=
=
=
=
=
=
:
=
=
is charged to within 1/2 lsb:
–
2µ
4.67µ
Amplifier Settling Time
1.37
–
2µs
T
10pF 1k
C
S
AMP
⎛
⎝
⎛
⎜
⎝
⎛
⎜
⎝
ACQUISITION TIME
S
HOLD
+
1
1 e
1 e
µs
) and the internal sampling
+
S
1.37µ
–
–
–
+
T
C
----------- -
2047
T
R
–
--------- -
–
-------- -
RC
+
RC
C
1
T
Tc
IC
S
HOLD
+
C
+
+
⎞
⎟
⎠
⎞
⎟
⎠
+
⎞
⎠
7k
HOLD
Temperature - 25°C 0.05µs/°C
T
=
R
COFF
=
) must be allowed
=
REF
50°C- 25°C 0.05µ
SS
+
. The sampling
V
V
V
+
) has no effect on the equation, since it cancels itself out.
A PP LIE D
CHOLD
10k
C HOLD
R
+
HOLD
S
Hold Capacitor Charging Time
ln(1/2047)
ln(0.0004885)
) is not discharged after each conversion.
Preliminary
⎛
⎝
1
–
----------- -
2047
S
/°C
1
⎞
⎠
As the impedance is decreased, the acquisition time
may be decreased. After the analog input channel is
selected (changed), this acquisition must be done
before the conversion can be started.
To
Equation 12-1 may be used. This equation assumes
that 1/2 LSb error is used (1024 steps for the A/D). The
1/2 LSb error is the maximum error allowed for the A/D
to meet its specified resolution.
To calculate the minimum acquisition time, T
the “PICmicro
Manual” (DS33023).
;[2] V
;combining [1] and [2]
;[1] V
calculate
CHOLD
CHOLD
®
+
Mid-Range MCU Family Reference
the
Temperature Coefficient
charge response to V
charged to within 1/2 lsb
minimum
PIC16F946
DS41265A-page 155
acquisition
APPLIED
ACQ
, see
time,