MB4053 Fujitsu Microelectronics, Inc., MB4053 Datasheet - Page 10

• Manufacturer Part Number: MB4053
• Description: 6-channel 8-bit A/D Converter
• Manufacturer: Fujitsu Microelectronics, Inc.

10
MB4053
Notes:
OPERATION DESCRIPTION
Refer to BLOCK DIAGRAM, and DIAGRAM. Address inputs A
converted, (one of the six analog inputs I
zero. This causes the external ramp capacitor C
the selected analog input voltage and a constant offset voltage V
switches from a logic 0 to logic 1 when the voltage on C
RAMP START input is switched back to a logic 1 after C
input from C
comparator reference voltage V
conversion cycle for 1 channel.
The time between the RAMP START input switching (0 1) and RAMP STOP output switching (1 0) is the
RAMP TIME t
was no comparator switching level error, leakage, switching delay times or effect of the impedance of the internal
reference current source. t
This ramp time is converted to a digital representation by counting t
can be tolerated, the A/D conversion software can be reduced and the conversion time minimized by omitting
corrections.
1 Charge slope =
2 Discharge slope =
Where: I
H
R
and allows it to be gin discharging at a fixed rate (Note 2). When the voltage on C
. This would be directly proportional to the analog input voltage for the ideal situation where there
A
is the acquisition current whose value is determined from the circuit constant in the IC.
R
I
A
–
can be calculated for the ideal case as follows:
C
– I
C
H
I
Where: V
R
R
H
BE2
the RAMP STOP output switches back to a logic 0. This completes a
t
C
R
I
R
IN
H
150 A – I
= V
=
1
= External ramp capacitor
= Analog input voltage to be measured
to I
IN
C
V
H
6
CC
). The RAMP START input is switched from a logic 1 to a logic
R
H
REF
-
C
I
R
V
R
to charge at a fixed rate. (Note 1) until it reaches the sum of
H
REF
H
H
reaches the comparator reference voltage V
is completely charged. This disconnects the analog
0
to A
BE1
2
. The RAMP STOP output (open-collector
R
are used to select the analog input to be
with the microprocessor. If a small error
H
reaches the
BE2
. The