Datasheet

ManualsBrandsTEXAS INSTRUMENTS ManualsPMICsPMIC - system monitor Reset/power-on reset TSSOP 8

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SLUS247F − APRIL 1997 − REVISED NOVEMBER 2007

 

  

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FEATURES

Fully Programmable Reset Threshold

D Fully Programmable Reset Period

D Fully Programmable Watchdog Period

D 2% Accurate Reset Threshold

D Input Voltage Down to 2 V

D Input 18-µA Maximum Input Current

D Reset Valid Down to 1 V

DESCRIPTION

The UCCx946 is designed to provide accurate

microprocessor supervision, including reset and

watchdog functions. During power up, the device

asserts a reset signal RES

with VDD as low as 1 V.

The reset signal remains asserted until the VDD

voltage rises and remains above the reset

threshold for the reset period. Both reset threshold

and reset period are programmable by the user.

The UCCx946 is also resistant to glitches on the

VDD line. Once RES

has been deasserted, any

drops below the threshold voltage need to be of

certain time duration and voltage magnitude to

generate a reset signal. These values are shown

in Figure 1. An I/O line of the microprocessor may

be tied to the watchdog input (WDI) for watchdog

functions. If the I/O line is not toggled within a set

watchdog period, programmable by the user,

WDO is asserted. The watchdog function is

disabled during reset conditions.

The UCCx946 is available in 8-pin SOIC(D), 8-pin

PDIP (N) and 8-pin TSSOP(PW) packages to

optimize board space.

UDG−0219

WDI

VDD

POWER TO

CIRCUITRY

CLK

CLR

8−BIT

COUNTER

400 nA

WDO

GND

EDGE DETECT

WATCHDOG

TIMING

100 mV

1.235 V

RTH

400 nA

POWER ON RESET

RES

S Q

1.235 V

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Summary of content (18 pages)

PAGE 1
SLUS247F − APRIL 1997 − REVISED NOVEMBER 2007 FEATURES D Fully Programmable Reset Threshold D Fully Programmable Reset Period D Fully Programmable Watchdog Period D 2% Accurate Reset Threshold D Input Voltage Down to 2 V D Input 18-µA Maximum Input Current D Reset Valid Down to 1 V The UCCx946 is also resistant to glitches on the VDD line.
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SLUS247F − APRIL 1997 − REVISED NOVEMBER 2007 ORDERING INFORMATION PACKAGED DEVICES(3) TA (D) (N) (PW) −40°C to 95°C UCC2946D UCC2946N UCC2946PW 0°C to 70°C UCC3946D UCC3946N UCC3946PW (1) The D and PW packages are also available taped and reeled. Add an R suffix to the device type (i.e., UCC2946DR) for quantities of 3,000 devices per reel. These devices have limited built-in ESD protection.
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SLUS247F − APRIL 1997 − REVISED NOVEMBER 2007 ELECTRICAL CHARACTERISTICS TA = 0°C to 70°C and 2.0 V ≤ VDD ≤ 5.5 V for the UCC3946, TA = −40°C to 95°C and 2.1 V ≤ VDD ≤ 5.5 V for the UCC2946, (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX UNIT REFERENCE VDD Operating voltage IDD Supply current VDD(min) Minimum operating voltage(1) UCC2946 2.1 5.5 UCC3946 2.0 5.5 UCC2946 12 18 UCC3946 10 18 UCC2946 1.1 UCC3946 1.
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SLUS247F − APRIL 1997 − REVISED NOVEMBER 2007 APPLICATION INFORMATION The UCCx946 supervisory circuit provides accurate reset and watchdog functions for a variety of microprocessor applications. The reset circuit prevents the microprocessor from executing code during undervoltage conditions, typically during power-up and power-down.
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SLUS247F − APRIL 1997 − REVISED NOVEMBER 2007 APPLICATION INFORMATION PROGRAMMING THE RESET VOLTAGE AND RESET PERIOD The UCCx946 allows the reset trip voltage to be programmed with two external resistors. In most applications VDD is monitored by the reset circuit, however, the design allows voltages other than VDD to be monitored. Referring to Figure 2, the voltage below which reset is asserted is determined by: V RESET + 1.
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SLUS247F − APRIL 1997 − REVISED NOVEMBER 2007 APPLICATION INFORMATION Once VDD rises above the programmed threshold, RES remains low for the reset period defined by: T RP + 3.125 C RP (2) where TRP is time in milliseconds and CRP is capacitance in nanofarads. CRP is charged with a precision current source of 400 nA, a high-quality, low-leakage capacitor (such as an NPO ceramic) should be used to maintain timing tolerances.
PAGE 7
SLUS247F − APRIL 1997 − REVISED NOVEMBER 2007 APPLICATION INFORMATION PROGRAMMING THE WATCHDOG PERIOD The watchdog period is programmed with CWP as follows: T WP + 25 C WP (3) where TWP is in milliseconds and CWP is in nanofarads. A high-quality, low-leakage capacitor should be used for CWP. The watchdog input WDI must be toggled with a high-to-low or low-to-high transition within the watchdog period to prevent WDO from assuming a logic level low.
PAGE 8
SLUS247F − APRIL 1997 − REVISED NOVEMBER 2007 APPLICATION INFORMATION CONNECTING WDO TO RES In order to provide design flexibility, the reset and watchdog circuits in the UCCx946 have separate outputs. Each output independently drives high or low, depending on circuit conditions explained previously. In some applications, it may be desirable for either the RES or WDO to reset the microprocessor. This can be done by connecting WDO to RES.
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE OPTION ADDENDUM www.ti.com 10-Jun-2014 (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production.
PAGE 11
PACKAGE OPTION ADDENDUM www.ti.
PAGE 12
PACKAGE MATERIALS INFORMATION www.ti.com 14-Jul-2012 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant UCC2946DTR SOIC D 8 2500 330.0 12.4 6.4 5.2 2.1 8.0 12.0 Q1 UCC2946PWTR TSSOP PW 8 2000 330.0 12.4 7.0 3.6 1.6 8.0 12.0 Q1 UCC3946DTR SOIC D 8 2500 330.0 12.4 6.4 5.2 2.1 8.0 12.
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PACKAGE MATERIALS INFORMATION www.ti.com 14-Jul-2012 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) UCC2946DTR SOIC D 8 2500 367.0 367.0 35.0 UCC2946PWTR TSSOP PW 8 2000 367.0 367.0 35.0 UCC3946DTR SOIC D 8 2500 367.0 367.0 35.0 UCC3946PWTR TSSOP PW 8 2000 367.0 367.0 35.
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IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete.