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Kingbor Technology Co.,Ltd
TEL:(86)0755-83095458 FAX:(86)0755-88364052
KB809
Microprocessor Reset circuits Features
* Under-voltage monitor * Power-on reset generation (180ms Typ) * Choice of threshold voltages (contact Kingbor regarding availability) * Active-low reset output * No external components required * Rejects brief input transients * Industry standard package and pinout * 3-pin SOT23-3 package
General Description
The KB809 is a power supply supervisor that provides under-voltage monitoring and power-on reset generation in an industry standard 3-pin SOT package and pinout. The reset output is asserted at power-on and any time the input voltage drops below the programmed threshold. It remains asserted for 180ms (typ.) after the input subsequently rises back above the threshold boundary. The KB809 has an active-low reset output. Hysteresis is included to prevent chattering due to noise, and the KB809 is inherently immune to brief power supply transients. Typical supply current is a low 3A. For those applications that require a manual reset function, see the KB811/812. For those applications that require a longer reset timeout, see the KB809. (The KB809 is identical to the industrystandard KB809 with the exception of a shorter reset timout.)
Applications
* Monitoring processor, ASIC, or FPGA core and I/O voltages * PDAs, hand-held PCs * Embedded controllers * Telecommunications systems * Power supplies * Wireless / Cellular systems * Networking hardware
Ordering Information
Part Number KB809-293 Part Number KB809-263 Marking** ADAA C956 Marking** AFAA C756 Typical Application Voltage* 3.3V 5% Typical Application Voltage* 3.3V 10% Nominal Threshold Voltage 2.93 Nominal Threshold Voltage 2.63 TRST (ms) 180 TRST (ms) 180 Junction Temperature Range -40C to +85C Junction Temperature Range -40 C to +85C Package SOT23-3 Package SOT23-3
Top Marking:
ADAA & AFAA: To manufacture marking after 2007-3-15 C956 & C756: Before 2007-3-15
Typical Application
VCC VCC
KB809
Block Diagrams
VCC
P
/RESET
/RESET
Typical Operating Circuit March 2007 1 KB809
Kingbor Technology Co.,Ltd
TEL:(86)0755-83095458 FAX:(86)0755-88364052
KB809
Pin Configuration
KB809
GND 1 3 VCC /RESET 2
3-Lead SOT23
Pin Description
Pin Number 1 2 Pin Name GND /RESET Pin Function Ground return for all IC functions. Digital Output. Active-low. Asserted whenever VCC falls below the threshold voltage. It will remain asserted for no less than 180ms and be de-asserted after VCC returns above the threshold. Analog Input. Power supply input to the IC.
3
VCC
2
March 2007
Kingbor Technology Co.,Ltd
TEL:(86)0755-83095458 FAX:(86)0755-88364052
KB809
Operating Ratings (Note 2)
Ambient Temperature (TA) ......................... -40C to +85C Power Dissipation (TA = +70C) .............................. 320mW
Absolute Maximum Ratings (Note 1)
Terminal Voltage (VCC) ................................. -0.3V to 10V Lead Temperature (soldering, 10 sec.) ..................... 300C Storage Temperature (TS) ......................... -65C to 150C Rate of Rise (VCC) ................................................. 100V/s ESD Rating, Note 3
Electrical Characteristics
TA = 25C; VCC = 3.3V for KB809 unless otherwise noted. Values in bold are for -40 C to +85 C; unless otherwise noted Symbol VCC ICC VTH Parameter Operating Voltage Range Condition TA = 0C to 70C TA = -40C to 85C Supply Current Reset Voltage Threshold Reset Voltage Threshold VHYST TRST TPROP VOH VOL Typical hysteresis Reset Timeout Period Propogation delay /RESET Output Voltage High /RESET Output Voltage Low /RESET < VOL, 100mV Overdrive ISOURCE = 500A VCC = VTH min., ISINK = 1.2mA VCC > 1.4V, ISINK = 50A, TA = 0C to +70C VCC > 1.6V, ISINK = 50A, TA = -40 to +85C
Note 1. Note 2. Note 3. Exceeding the absolute maximum rating may damage the device. The device is not guaranteed to function outside its operating rating. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF.
Min 0.95 0.95
Typ
Max 8 8
Units V V A V V mV
VCC = 3.3V S Voltage Options (KB809-293) S Voltage Options (KB809-263) 2.85 2.55
1 2.93 2.63 5 140 180 9.3 0.8*VCC
3 3.00 2.70
300
ms s V
0.3 0.3 0.3
V V V
Timing Diagrams
VCC VTH TRST RESET VTH TRST
Reset Timing Diagram
March 2007
3
Kingbor Technology Co.,Ltd
TEL:(86)0755-83095458 FAX:(86)0755-88364052
KB809
Functional Diagram
VCC (3) VTH
+ -
RESET GENERATOR
RESET (2)
GND (1)
KB809 Block Diagram
Standard Circuits
4
March 2007
Kingbor Technology Co.,Ltd
TEL:(86)0755-83095458 FAX:(86)0755-88364052
KB809
VCC
Applications Information
Microprocessor Reset The /RESET pin is asserted whenever VCC falls below the reset threshold voltage. The /RESET pin remains asserted for a period of 180ms after VCC has risen above the reset threshold voltage. The reset function ensures the microprocessor is properly reset and powers up in a known condition after a power failure. /RESET will remain valid with VCC as low as 0.95V. Transients on VCC The KB809 is inherently immune to very short "glitches" on VCC. In the case of very brief transients, VCC may drop below the under-voltage threshold without triggering a reset. As shown in the graph of Figure 1, the narrower the transient, the deeper the threshold overdrive that will be ignored. The line on the graph represents the typical allowable transient duration for a given amount of threshold overdrive that will not generate a reset. The data from which Figure 1 is derived was taken by adding negative-going square-wave pulses to a DC input voltage set at 0.5V above the actual measured threshold for the part being characterized.
Typical Transient Response
MAX. TRANSIENT DURATION (s)
VCC VIN KB809 /RESET GND RPULL-DOWN 100k /RESET INPUT Microcontroller or Microprocessor GND
Figure 2. Ensuring a Valid /RESET Signal at Low Voltage Interfacing to Processors with Bidirectional Reset Pins Some microprocessors have reset signal pins that are bidirectional, rather than input only. The Motorola 68HC11 family is one example. To prevent excessive current flow when the processor asserts its reset output, a series resistor is employed between the KB809's output and the reset pin. This limits the current that will flow between the KB809 and the reset pin to a theoretical maximum of VCC/RSERIES. Because this resistor also limits the drive capability of the supervisor's output, a buffer may be required to drive additional circuitry. See Figure 3.
BUFFER RESET SIGNAL to OTHER CIRCUITS VCC
20 VTH = 2.932 15
10
5
0 0 200 400 600 RESET COMP. OVERDRIVE, VTH -VCC (mV)
VIN KB809 /RESET GND 4.7k
VCC
Figure 1. Comparator Overdrive vs. Duration Ensuring Proper Operation at Low VCC At levels of VCC below 1.4V, the KB809's output driver cannot always turn on sufficiently to produce a valid logic-low. In this situation, other circuits driven by /RESET could be allowed to float, causing undesired operation. (In most cases, however, it is expected that the circuits driven by the KB809 will be similarly inoperative at V CC =0.95V.) If a given application requires that /RESET be valid below VCC =1.4V, this can be accomplished by adding a pull-down resistor to the output. A value of 100k is recommended, as this is usually an acceptable compromise of leakage current and pull-down current. The resistor's value is not critical, however. See Figure 2.
RESET I/O Microcontroller or Microprocessor GND
Figure 3. Interfacing to Processors with Bidirectional Reset Pins
March 2007
5
Kingbor Technology Co.,Ltd
TEL:(86)0755-83095458 FAX:(86)0755-88364052
KB809
PACAGE DESCRIPTION
0.021 0.015
0.055 0.047
0.098 0.083
0.120 0.105 0.040 0.031 0.079 0.071 0.004 0.001
0.0059 0.0035
0-81/4
0.010 0.005
3-lead SOT-23
Kingbor Technology
TEL:(86) 0755-83095458 FAX: (86) 0755-88364052 www.kingbor.com
6
March 2007

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