MCP1726T-ADJZEMF Microchip Technology, MCP1726T-ADJZEMF Datasheet - Page 71

• Manufacturer Part Number: MCP1726T-ADJZEMF
• Description: Regulator, Extended Industrial, HVSON, 8-Pin|
• Manufacturer: Microchip Technology

10.2
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 10-4. The
source impedance (R
switch (R
required to charge the capacitor C
switch (R
(V
mended impedance for analog sources is 10 k .
EQUATION 10-1:
FIGURE 10-4:
 2003 Microchip Technology Inc.
DD
Note 1: The reference voltage (V
Legend C
), see Figure 10-4. The maximum recom-
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
T
SS
ACQ
) impedance varies over the device voltage
ACQ
leakage specification.
) impedance directly affect the time
T
V
I
R
SS
C
C
LEAKAGE
T
PIN
IC
HOLD
=
=
=
=
=
=
=
=
-120pF 1k
Amplifier Settling Time
2µs
C
16.47µs
T
2µ
19.72µs
AMP
HOLD
VA
ACQUISITION TIME
ANALOG INPUT MODEL
S
S
= Input Capacitance
= Threshold Voltage
= Leakage Current at the pin due to
= Interconnect Resistance
= Sampling Switch
= Sample/Hold Capacitance (from DAC)
) and the internal sampling
+
+
R
various junctions
S
+
T
16.47µ
C
T
ANx
R
+
C
C
5 pF
IC
HOLD
+
PIN
+
S
+
HOLD
Temperature - 25°C 0.05µs/°C
T
7k
+
COFF
) must be allowed
R
REF
SS
. The sampling
50°C- 25°C 0.05µ
+
) has no effect on the equation, since it cancels itself out.
+
10k
R
Advance Information
+
HOLD
S
V
DD
Hold Capacitor Charging Time
In(1/2047)
V
V
) is not discharged after each conversion.
T
T
In(0.0004885)
= 0.6V
= 0.6V
S
/°C
I
± 500 nA
LEAKAGE
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 10-1 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
(DS33023).
R
IC
calculate
PICmicro
1k
V
SS R
Sampling
Switch
DD
6V
5V
4V
3V
2V
®
+
SS
the
Temperature Coefficient
Mid-Range
Sampling Switch
5 6 7 8 9 10 11
V
minimum
SS
C
= DAC capacitance
= 120 pF
(k )
HOLD
PIC12F683
Reference
acquisition
DS41211A-page 69
ACQ
Manual
, see
time,