Datasheet

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

FEATURES

DESCRIPTION

UDG−02192

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

Q R

S Q

1.235 V

UCC2946-Q1

www.ti.com

................................................................................................................................................. SGLS273B – OCTOBER 2004 – REVISED MARCH 2009

MICROPROCESSOR SUPERVISOR WITH WATCHDOG TIMER

• Qualified for Automotive Applications • 2% Accurate Reset Threshold

• Fully Programmable Reset Threshold • Input Voltage Down to 2 V

• Fully Programmable Reset Period • Input 18- µ A Maximum Input Current

• Fully Programmable Watchdog Period • Reset Valid Down to 1 V

The UCC2946 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 UCC2946 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 UCC2946 is available in 8-pin TSSOP (PW) package to optimize board space.

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas

Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.

Summary of content (15 pages)

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UCC2946-Q1 www.ti.com .................................................................................................................................................
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UCC2946-Q1 SGLS273B – OCTOBER 2004 – REVISED MARCH 2009 ................................................................................................................................................. www.ti.com These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates.
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UCC2946-Q1 www.ti.com .................................................................................................................................................
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UCC2946-Q1 SGLS273B – OCTOBER 2004 – REVISED MARCH 2009 ................................................................................................................................................. www.ti.com APPLICATION INFORMATION The UCC2946 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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UCC2946-Q1 www.ti.com ................................................................................................................................................. SGLS273B – OCTOBER 2004 – REVISED MARCH 2009 Programming the Reset Voltage and Reset Period The UCC2946 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.
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UCC2946-Q1 SGLS273B – OCTOBER 2004 – REVISED MARCH 2009 ................................................................................................................................................. www.ti.com TRP RES TRP 5V 0V 5V VDD Monitored by RT 2.5 V Programmed Threshold 1V 0V t1 t2 t3 t4 t5 t6 t7 t1: VDD > 1 V, RES is ensured low. t2: VDD > programmed threshold, RES remains low for TRP. t3: TRP expires, RES pulls high.
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UCC2946-Q1 www.ti.com ................................................................................................................................................. SGLS273B – OCTOBER 2004 – REVISED MARCH 2009 Programming the Watchdog Period The watchdog period is programmed with CWP as shown in Equation 3: TWP = 25 × CWP (3) Where TWP is in milliseconds CWP is in nanofarads A high-quality, low-leakage capacitor should be used for CWP.
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UCC2946-Q1 SGLS273B – OCTOBER 2004 – REVISED MARCH 2009 ................................................................................................................................................. www.ti.com Connecting WDO to RES To provide design flexibility, the reset and watchdog circuits in the UCC2946 have separate outputs. Each output independently drives high or low, depending on circuit conditions explained previously.
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UCC2946-Q1 www.ti.com ................................................................................................................................................. SGLS273B – OCTOBER 2004 – REVISED MARCH 2009 TYPICAL CHARACTERISTICS INPUT CURRENT vs INPUT VOLTAGE THRESHOLD RESISTANCE vs AMBIENT TEMPERATURE 12.0 1.26 1.25 11.5 1.24 11.0 IDD − Input Current − µA VRTH − Threshold Resistance − V VDD = 5 V 1.23 1.22 10.0 9.5 1.21 1.20 −55 10.5 9.
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PACKAGE OPTION ADDENDUM www.ti.com 24-Jan-2013 PACKAGING INFORMATION Orderable Device Status (1) UCC2946TPWRQ1 ACTIVE Package Type Package Pins Package Qty Drawing TSSOP PW 8 2000 Eco Plan Lead/Ball Finish (2) Green (RoHS & no Sb/Br) MSL Peak Temp Op Temp (°C) Top-Side Markings (3) CU NIPDAU Level-2-260C-1 YEAR (4) -40 to 105 2946T (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs.
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE MATERIALS INFORMATION www.ti.com 14-Mar-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device UCC2946TPWRQ1 Package Package Pins Type Drawing TSSOP PW 8 SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) 2000 330.0 12.4 Pack Materials-Page 1 7.0 B0 (mm) K0 (mm) P1 (mm) 3.6 1.6 8.0 W Pin1 (mm) Quadrant 12.
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PACKAGE MATERIALS INFORMATION www.ti.com 14-Mar-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) UCC2946TPWRQ1 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.