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UCC2946D

Part # UCC2946D
Description MICRO SUPER W/ WATCHDOG TIMER- Rail/Tube
Category IC
Availability In Stock
Qty 385
Qty Price
1 - 80 $2.76393
81 - 161 $2.19858
162 - 242 $2.07295
243 - 323 $1.92638
324 + $1.71699
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Technical Document


DISCLAIMER: The information provided herein is solely for informational purposes. Customers must be aware of the suitability of this product for their application, and consider that variable factors such as Manufacturer, Product Category, Date Codes, Pictures and Descriptions may differ from available inventory.



SLUS247F − APRIL 1997 − REVISED NOVEMBER 2007
7
www.ti.com
APPLICATION INFORMATION
PROGRAMMING THE WATCHDOG PERIOD
The watchdog period is programmed with C
WP
as follows:
T
WP
+ 25 C
WP
where T
WP
is in milliseconds and C
WP
is in nanofarads. A high-quality, low-leakage capacitor should be used
for C
WP
. 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. WDO maintains the low logic level until WDI
is toggled or RES
is asserted. If at any time RES is asserted, WDO assumes a high logic state and the watchdog
period be reinitiated. Figure 4 illustrates the timings associated with the watchdog circuit.
0V
VDD
t1
0V
VDD
VDD
0V
t2 t3 t4 t5 t6 t7 t8 t9 t10 t11 t12 t13 t14
RESET
WDI
WDO
T
RP
T
WP
UDG−98007
t1: Microprocessor is reset.
t2: WDI is toggled some time after reset, but before TWP expires.
t3: WDI is toggled before T
WP
expires.
t4: WDI is toggled before T
WP
expires.
t5: WDI is not toggled before TWP expires and WDO
asserts low, triggering the microprocessor to enter an error recovery routine.
t6: The microprocessor’s error recovery routine is executed and WDI is toggled, reinitiating the watchdog timer.
t7: WDI is toggled before T
WP
expires.
t8: WDI is toggled before T
WP
expires.
t9: RES
is momentarily triggered, RES is asserted low for TRP.
t10: Microprocessor is reset, RES
pulls high.
t11: WDI is toggled some time after reset, but before T
WP
expires.
t12: WDI is toggled before T
WP
expires.
t13: WDI is toggled before T
WP
expires.
t14: VDD dips below the reset threshold, RES
is asserted.
Figure 4. Watchdog Circuit Timings
(3)


SLUS247F − APRIL 1997 − REVISED NOVEMBER 2007
8
www.ti.com
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. If the pins try to drive to different output levels, the low output level dominates.
Additional current flows from VDD to GND during these states. If the application cannot support additional
current (during fault conditions), RES
and WDO can be connected to the inputs of an OR gate whose output
is connected to the microprocessor’s reset pin.
LAYOUT CONSIDERATIONS
A 0.1-µF capacitor connected from VDD to GND is recommended to decouple the UCCx946 from switching
transients on the VDD supply rail.
Since RP and WP are precision current sources, capacitors C
RP
and C
WP
should be connected to these pins
with minimal trace length to reduce board capacitance. Care should be taken to route any traces with high
voltage potential or high speed digital signals away from these capacitors.
Resistors R1 and R2 generally have a high ohmic value, traces associated with these parts should be kept short
in order to prevent any transient producing signals from coupling into the high impedance RTH pin.
TYPICAL CHARACTERISTICS
Figure 5.
THRESHOLD RESISTANCE
vs
AMBIENT TEMPERATURE
V
RTH
− Threshold Resistance − V
T
A
− Ambient Temperature − °C
−55
1.22
1.20
−35 −15 5 25 45 65 85 105 125
1.21
1.25
1.23
1.24
1.26
V
DD
= 5 V
2
10.0
9.0
3456
9.5
11.5
10.5
11.0
12.0
Figure 6.
V
DD
− Input Voltage − V
INPUT CURRENT
vs
INPUT VOLTAGE
I
DD
− Input Current − µA
PACKAGING INFORMATION
Orderable Device Status
(1)
Package
Type
Package
Drawing
Pins Package
Qty
Eco Plan
(2)
Lead/Ball Finish MSL Peak Temp
(3)
UCC2946D ACTIVE SOIC D 8 75 Green (RoHS &
no Sb/Br)
CU NIPDAU Level-2-260C-1 YEAR
UCC2946DG4 ACTIVE SOIC D 8 75 Green (RoHS &
no Sb/Br)
CU NIPDAU Level-2-260C-1 YEAR
UCC2946DTR ACTIVE SOIC D 8 2500 Green (RoHS &
no Sb/Br)
CU NIPDAU Level-2-260C-1 YEAR
UCC2946DTRG4 ACTIVE SOIC D 8 2500 Green (RoHS &
no Sb/Br)
CU NIPDAU Level-2-260C-1 YEAR
UCC2946PW ACTIVE TSSOP PW 8 150 Green (RoHS &
no Sb/Br)
CU NIPDAU Level-2-260C-1 YEAR
UCC2946PWG4 ACTIVE TSSOP PW 8 150 Green (RoHS &
no Sb/Br)
CU NIPDAU Level-2-260C-1 YEAR
UCC2946PWTR ACTIVE TSSOP PW 8 2000 Green (RoHS &
no Sb/Br)
CU NIPDAU Level-2-260C-1 YEAR
UCC2946PWTRG4 ACTIVE TSSOP PW 8 2000 Green (RoHS &
no Sb/Br)
CU NIPDAU Level-2-260C-1 YEAR
UCC3946D ACTIVE SOIC D 8 75 Green (RoHS &
no Sb/Br)
CU NIPDAU Level-2-260C-1 YEAR
UCC3946DG4 ACTIVE SOIC D 8 75 Green (RoHS &
no Sb/Br)
CU NIPDAU Level-2-260C-1 YEAR
UCC3946DTR ACTIVE SOIC D 8 2500 Green (RoHS &
no Sb/Br)
CU NIPDAU Level-2-260C-1 YEAR
UCC3946DTRG4 ACTIVE SOIC D 8 2500 Green (RoHS &
no Sb/Br)
CU NIPDAU Level-2-260C-1 YEAR
UCC3946N ACTIVE PDIP P 8 50 Green (RoHS &
no Sb/Br)
CU NIPDAU N / A for Pkg Type
UCC3946NG4 ACTIVE PDIP P 8 50 Green (RoHS &
no Sb/Br)
CU NIPDAU N / A for Pkg Type
UCC3946PW ACTIVE TSSOP PW 8 150 Green (RoHS &
no Sb/Br)
CU NIPDAU Level-2-260C-1 YEAR
UCC3946PWG4 ACTIVE TSSOP PW 8 150 Green (RoHS &
no Sb/Br)
CU NIPDAU Level-2-260C-1 YEAR
UCC3946PWTR ACTIVE TSSOP PW 8 2000 Green (RoHS &
no Sb/Br)
CU NIPDAU Level-2-260C-1 YEAR
UCC3946PWTRG4 ACTIVE TSSOP PW 8 2000 Green (RoHS &
no Sb/Br)
CU NIPDAU Level-2-260C-1 YEAR
(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. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check
http://www.ti.com/productcontent for the latest availability information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements
for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered
at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and
PACKAGE OPTION ADDENDUM
www.ti.com
18-Sep-2008
Addendum-Page 1
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