SH3000 SEMTECH [Semtech Corporation], SH3000 Datasheet - Page 5

• Manufacturer Part Number: SH3000
• Description: Low-Power Programmable Multifunction Support IC for Microcontrollers
• Manufacturer: SEMTECH [Semtech Corporation]

CPU Supervisor
manage the reset of the target processor, a low V
monitor (Brownout Detector) and a Watchdog Timer, see
Figure 1.
Management System to provide a more complete
system solution than the stand-alone components.
The SH3000 has both active high and active low reset
output pins. Both are driven strong to the active state
and weak to the inactive state. This eliminates the need
for external pull-ups and allows various reset sources to
be connected together in a wire-OR configuration. (This
makes it simple to set up a manual reset circuit.)
source of the reset to the system software.
Low V
V
threshold, programmable from 2.3 V to 4.3 V in average
steps of 33 mV, see Table 1.
Table 1. Programmable V
Parameter
VBO for min code
(000000)
VBO for max code
(111111)
Step resolution
Copyright ©2003-2005 Semtech Corporation
SYSTEM MANAGEMENT
DD
Temperature-
compensated
Reference
Lock Logic
Voltage
The SH3000 has two supervisory functions that
Both functions are integrated with the Clock
A set of flags in the register map indicates the
The SH3000 drives the reset pins active whenever
is below the value of V
DD
V
1
DD
Reset
4.40 V
2.30 V
Figure 1. CPU Supervisor --- Low V
Noise Filter
V
V
HIGH
LOW
6-bit Value
Threshold
D/A
Min
2.27
4.2
25
BO
BO
, the brownout reset
Values
Typ
2.3
4.3
33
Hysteresis
50mV
Initialization Logic
TYP
Max
2.33
4.4
41
Write-once
.
CLK
DD
R
32kHz
ESET
Units
V
V
mV
DD
OUT
/ Brownout Detector, Watchdog, Reset logic & Drivers
Mode
PWR
5
32kHz
OK
the factory-programmed OTP nonvolatile memory. It
can be re-programmed at any time or it can be
permanently protected from any changes by setting the
V
reset signals are driven active. These outputs are
typically valid for a V
guaranteed to be valid for a V
stays above the level of (V
a small fixed amount of hysteresis, nominally 50 mV,
added to prevent nuisance reset activations (when V
slowly changes near the level of V
power glitching is present).
considered valid. In case of the initial power-up, the
reset is then driven inactive once 6 ms of valid power
have elapsed. In the case of brownout, the reset is
released after a delay of 6 ms (but no less than 12 ms
from the beginning of the brownout).
provides a fast-starting clock that is free of crystal start-
up time requirements. This gives the SH3000 an
advantage over most external reset circuits, which must
have a long reset pulse duration to accommodate long
and unpredictable crystal start-up times.
clock is available 2 ms before the reset signals are
negated, so that internal synchronous reset and
initialization of the target micro can proceed normally.
÷
BO
256
The default V
On power up both the active-high and active-low
The reset outputs remain active until V
At the level of (V
Such a fast reset is possible because the SH3000
The SH3000 guarantees that a valid and stable
Lock flag or an OTP write-protect flag.
Duration Timer
Reset Logic
U
NDERFLOW
Minimum
7-bit Down Counter
&
7-bit Watchdog
Timeout Value
÷
BO
1→0
128
DD
BO
value is loaded on power-up from
SH3000 MicroBuddy™
level of at least 0.5 V, and
+ V
BO
Load
HYST
V
V1.15
DD
+ V
DD
20
) the power supply is
R
level of 1.0 V.
HYST
ESET
K
BO
Reload Control
Alternating Codes
and some noise or
), where V
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Watchdog
0x5A / 0xC3
20
K
Logic
DD
rises and
HYST
From / To
Serial I/O
RST
N
11
10
RST
DD
is