SH3003 Datasheet, PDF (10/30 Pages) Semtech Corporation – MicroBuddy® Support IC for Microcontrollers

SH3003
POWER MANAGEMENT
Application Information (continued)
CPU Supervisor
Not authorized for release outside of Semtech - DRAFT
Low VDD Reset
The SH3003 has two supervisory functions that man-
age the reset of the target processor, a low VDD monitor
(Brownout Detector) and a Watchdog Timer, see Figure 1.
Both functions are integrated with the Clock Management
System to provide a more complete system solution than
stand-alone components.
The SH3003 drives the reset pins active whenever VDD is
below the value of VBO, the brownout reset threshold, pro-
grammable from 2.3V to 4.3V in average steps of 33mV,
see Table 1.
Parameter
Min Typ Max Units
The SH3003 has both active high and active low reset ^{VBO for min code}
output pins. Both are driven strong to the active state and ^(000000)
2.27
2.3
2.33
V
weak to the inactive state. This eliminates the need for ex-
ternal pull-ups and allows various reset sources to be con-
nected together in a wire-OR configuration. (This makes it
VBO for max code
(111111)
4.2
4.3
4.4
V
simple to set up a manual reset circuit.)
Step resolution
33
mV
A set of flags in the register map indicates the source of
the reset to the system software.
Table 1
The default VBO value is loaded on power-up from the fac-
tory-programmed non-volatile memory. It can be re-pro-
grammed at any time or it can be permanently protected
from any changes by setting the VBO Lock flag or a write-
protect flag.
VDD Noise Filter
3
Temperature- ^{4.40 V} _VHIGH
compensated
Threshold
Voltage
Reference
2.30 V _VLOW
D/A
Lock Logic
6-bit Value
RESET
CLKOUT
Hysteresis
50mV TYP.
32 kHz
Write-once
Initialization Logic
32kHz
PWROK
Reset Logic
&
Minimum
Duration Timer
UNDERFLOW 1 0
RESET
VDD
20K
20K
RST
11
NRST
10
Mode
7-bit Down Counter
256
128
Load
7-bit Watchdog
Timeout Value
Watchdog
Reload Control
Alternating Codes
Logic
0x5A / 0xC3
Figure 1. CPU Supervisor --- Low VDD / Brownout Detector, Watchdog, Reset logic & Drivers
From / To
Serial I/O
©2006 Semtech Corp.
10
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