PIC18F2331_10 Datasheet, PDF (250/392 Pages) Microchip Technology – 28/40/44-Pin Enhanced Flash Microcontrollers with nanoWatt Technology, High-Performance PWM and A/D

PIC18F2331/2431/4331/4431
EXAMPLE 21-1: CALCULATING THE MINIMUM REQUIRED ACQUISITION TIME
TACQ = TAMP + TC + TCOFF
TAMP = Negligible
TCOFF = (Temp – 25°C)(0.005 s/°C)
(50°C – 25°C)(0.005 s/°C) = .13 s
Temperature coefficient is only required for temperatures > 25°C. Below 25°C, TCOFF = 0 s.
TC
= -(CHOLD) (RIC + RSS + RS) ln(1/2047) s
-(9 pF) (1 k + 6 k + 100) ln(0.0004883) s = .49 s
TACQ = 0 + .49 s + .13 s = .62 s
Note: If the converter module has been in Sleep mode, TAMP is 2.0 s from the time the part exits Sleep mode.
FIGURE 21-2:
ANALOG INPUT MODEL
VDD
Rs ^ANx
VT = 0.6V
RIC 1k
Sampling
Switch
SS _RSS
VAIN
CPIN
5 pF
VT = 0.6V
ILEAKAGE
±100 nA
CHOLD = 9 pF
VSS
Legend:
CPIN
= Input Capacitance
VT
= Threshold Voltage
ILEAKAGE = Leakage Current at the pin due to
various junctions
RIC
= Interconnect Resistance
SS
= Sampling Switch
CHOLD = Sample/Hold Capacitance (from DAC)
RSS
= Sampling Switch Resistance
6V
5V
VDD 4V
3V
2V
5 6 7 8 9 10 11
Sampling Switch (k)
Note: For VDD < 2.7V and temperatures below 0°C, VAIN should be restricted to range: VAIN < VDD/2.
DS39616D-page 250
 2010 Microchip Technology Inc.