TCM809 Microchip Technology, Inc., TCM809 Datasheet - Page 4

• Manufacturer Part Number: TCM809
• Description: The TCM809 And TCM810 Are Cost-effective System Supervisor Circuits Designed to Monitor VCC in Digital Systems And Provide a Reset Signal to The Host Processor When Necessary
• Manufacturer: Microchip Technology, Inc.

TCM809/TCM810
2.0
2.1
The TCM809/TCM810 provides accurate V
ing and reset timing during power-up, power-down, and
brownout/sag conditions. These devices also reject
negative-going transients (glitches) on the power sup-
ply line. Figure 2-1 shows the maximum transient dura-
tion vs. maximum negative excursion (overdrive) for
glitch rejection. Any combination of duration and over-
drive which lies under the curve will not generate a
reset signal.
FIGURE 2-1:
Overdrive for Glitch Rejection at 25°C.
DS21661B-page 4
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1
APPLICATIONS INFORMATION
V
400
320
240
160
80
DD
0
1
TCM8XXZ/R/S/T
(SOT-23)
Transient Rejection
T
Maximum
A
V
DD
= +25°C
Reset Comparator Overdrive (mV)
Reset Comparator Overdrive
[V
10
TH
5
[V
- V
Duration
TH
TCM8XXL/M/J (SOT-23)
DD
- V
Transient
] (mv)
DD
] (mv)
Overdrive
TCM8XXZ/R/S/T (SC-70)
100
V
100
TH
TCM8XXL/M/J (SC-70)
Duration
DD
1000
monitor-
1000
vs.
Combinations above the curve are detected as a
brownout or power-down condition. Transient immunity
can be improved by adding a capacitor in close proxim-
ity to the V
2.2
The TCM809 RESET output is valid to V
Below this voltage the output becomes an "open cir-
cuit" and does not sink current. This means CMOS
logic inputs to the microcontroller will be floating at an
undetermined voltage. Most digital systems are com-
pletely shutdown well above this voltage. However, in
situations where RESET must be maintained valid to
V
RESET to ground to discharge stray capacitances and
hold the output low (Figure 2-2). This resistor value,
though not critical, should be chosen such that it does
not appreciably load RESET under normal operation
(100 k
larly, a pull-up resistor to V
TCM810 to ensure a valid high RESET for V
1.0V.
FIGURE 2-2:
output of the TCM809 ensures that the RESET output
is valid to V
DD
= 0V, a pull-down resistor must be connected from
RESET Signal Integrity During
Power-Down
will be suitable for most applications). Simi-
DD
DD
pin of the TCM809/TCM810.
= 0V.
The addition of R
TCM809
GND
V
V
DD
DD
RESET
2002 Microchip Technology Inc.
DD
is required for the
R
100 k
1
1
at the RESET
DD
DD
= 1.0V.
below