SH3003 datasheet(10/30 Pages) SEMTECH

10 / 30 page

SH3003

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POWER MANAGEMENT

Parameter

Min

Typ

Max

Units

VBO for min code

(000000)

2.27

2.3

2.33

VBO for max code

(111111)

4.2

4.3

4.4

Step resolution

Application Information (continued)

CPU Supervisor

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 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 ex-

ternal pull-ups and allows various reset sources to be con-

nected together in a wire-OR conﬁguration. (This makes it

simple to set up a manual reset circuit.)

A set of ﬂags in the register map indicates the source of

the reset to the system software.

Table 1

Low VDD Reset

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.

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.

Figure 1. CPU Supervisor --- Low VDD / Brownout Detector, Watchdog, Reset logic & Drivers

Noise Filter

VDD

VHIGH

VLOW

Threshold

D/A

4.40 V

2.30 V

Hysteresis

50mV TYP.

Reset Logic

Minimum

Duration Timer

PWROK

Temperature-

compensated

Voltage

Reference

RST

VDD

20K

UNDERFLOW 1

32kHz

256

32 kHz

CLKOUT

7-bit Down Counter

128

Mode

6-bit Value

7-bit Watchdog

Timeout Value

Watchdog

Reload Control

Alternating Codes

Logic

0x5A / 0xC3

Load

From / To

Serial I/O

Write-once

Initialization Logic

Lock Logic

RESET

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