PIC16LC923-04/PT Microchip Technology, PIC16LC923-04/PT Datasheet - Page 82

• Manufacturer Part Number: PIC16LC923-04/PT
• Description: IC MCU OTP 4KX14 LCD DVR 64TQFP
• Manufacturer: Microchip Technology
• Series: PIC® 16Cr

Specifications of PIC16LC923-04/PT

• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 4MHz
• Connectivity: I²C, SPI
• Peripherals: LCD, POR, PWM, WDT
• Number Of I /o: 25
• Program Memory Size: 7KB (4K x 14)
• Program Memory Type: OTP
• Ram Size: 176 x 8
• Voltage - Supply (vcc/vdd): 2.5 V ~ 6 V
• Oscillator Type: External
• Operating Temperature: 0°C ~ 70°C
• Package / Case: 64-TFQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Data Converters: -

PIC16C9XX
12.1
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
impedance directly affect the time required to charge
the capacitor C
ance
(Figure 12-4). The source impedance affects the offset
voltage at the analog input (due to pin leakage current).
The maximum recommended impedance for ana-
log sources is 10 k . 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 calculates
the acquisition time to within 1/2 LSb error (512 steps
for the A/D). The 1/2 LSb error is the maximum error
allowed for the A/D to meet its specified accuracy.
EQUATION 12-1:
V
Given: V
The above equation reduces to:
T
Example 12-1 shows the calculation of the minimum
required acquisition time (T
based on the following system assumptions.
C
Rs = 10 k
1/2 LSb error
V
Temp (system max.) = 50 C
V
FIGURE 12-4: ANALOG INPUT MODEL
DS30444E - page 82
HOLD
C
HOLD
DD
HOLD
= -(51.2 pF)(1 k - R
= 5V
calculate
= (V
= 51.2 pF
= 0 @ t = 0
varies
HOLD
A/D Acquisition Requirements
REF
= (V
Rss = 7 k
S
- (V
HOLD
) and the internal sampling switch (R
over
REF
REF
the
Legend C
/512), for 1/2 LSb resolution
. The sampling switch (R
/512)) • (1 - e
SS
VA
A/D MINIMUM CHARGING
TIME
the
minimum
+ R
Rs
V
I leakage
R
SS
C
T
PIN
IC
HOLD
S
) ln(1/511)
device
ACQ
RAx
C
5 pF
HOLD
(-Tc/C
PIN
). This calculation is
= input capacitance
= threshold voltage
= leakage current at the pin due to
= interconnect resistance
= sampling switch
= sample/hold capacitance (from DAC)
various junctions
acquisition
) must be allowed
HOLD
voltage
(R
IC
+ R
SS
V
) imped-
SS
DD
(V
+ R
V
V
time,
T
DD
T
S
SS
= 0.6V
= 0.6V
))
)
),
)
I leakage
500 nA
EXAMPLE 12-1: CALCULATING THE
T
T
T
T
R
ACQ
ACQ
C
ACQ
IC
Note 1: The reference voltage (V
Note 2: The charge holding capacitor (C
Note 3: The maximum recommended impedance
Note 4: After a conversion has completed, a
=
1k
= Amplifier Settling Time +
= 5 s + Tc + [(Temp - 25 C)(0.05 s/ C)]
= 5 s + 5.747 s + [(50 C - 25 C)(0.05 s/ C)]
Holding Capacitor Charging Time +
Temperature Coefficient
-C
-51.2 pF (1 k + 7 k + 10 k ) ln(0.0020)
-51.2 pF (18 k ) ln(0.0020)
-0.921 s (-6.2364)
5.747 s
10.747 s + 1.25 s
11.997 s
V
SS R
DD
HOLD
Sampling
Switch
effect on the equation, since it cancels
itself out.
not discharged after each conversion.
for analog sources is 10 k . This is
required to meet the pin leakage specifi-
cation.
2.0 T
acquisition can begin again. During this
time the holding capacitor is not con-
nected to the selected A/D input channel.
6V
5V
4V
3V
2V
SS
(R
AD
IC
MINIMUM REQUIRED
SAMPLE TIME
Sampling Switch
5 6 7 8 9 10 11
+ R
delay must complete before
V
SS
C
= DAC capacitance
= 51.2 pF
( k )
SS
HOLD
1997 Microchip Technology Inc.
+ R
S
) ln(1/511)
REF
) has no
HOLD
) is