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YB1921
3-Pin Microprocessor Reset Monitor
Introduction
The YB1921 is a cost-effective system
supervisor Integrated Circuit (IC) designed to monitor
VCC in digital and mixed signal systems and provide a
warning signal when the system power supply is out
of working range, and a reset signal to the host
processor when necessary. No external components
are required.
The reset output is driven active within 20μsec
of VCC falling through the reset voltage threshold.
Reset is maintained active for a minimum of 140msec
after VCC rises above the reset threshold. The YB1921
has an active-low RESET output. The output of the
YB1921 is guaranteed valid down to VCC=1V.
The YB1921 is optimized to reject fast transient
glitches on the VCC line. Low supply current of 18μA
(VCC=3.3V) makes these devices suitable for battery
powered applications.
Features
z Precision VCC Monitor for 2.8V, 3.0V, 3.3V,
and 5.0V Supplies
z 140msec Guaranteed Minimum RESET
Output Duration
z RESET Output Guaranteed to VCC=1.0V
z Low 18μA Supply Current
z VCC Transient Immunity
z Small SOT-23 Package
z No External Components
z Wide Operating Temperature: 0°C to 85°C
Applications
z Computers
z Embedded systems
z Battery powered equipment
z Critical µP power supply monitoring
Application Diagram
YB1921
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Absolute Maximum Ratings (1)
Parameter
Input Voltage
Output Voltage
Input Current
Output Current
Power Dissipation
Output Short Circuit Duration
Thermal Resistance, Junction-to-Ambient
Operating Temperature Range
Lead Temperature (Soldering, 10 sec.)
Junction Temperature
Storage Temperature
YB1921
3-Pin Microprocessor Reset Monitor
Symbol
VCC
RESET
IOUT
PD
ΘJA
TA
TJ
TS
Value
Value
5.5
-0.3 to (Vcc+0.3)
20
20
Internally Limited (3)
Infinite
230
0~85
260
0 to+125
-60 to+150
Unit
V
V
mA
mA
°C/W
°C
°C
°C
°C
Recommended Operating Conditions (2)
Parameter
Symbol
Power Supply Voltage
Junction Temperature
VCC
TJ
Min
2.0
0
Value
Type.
Max
5.5
+125
Unit
V
°C
YB1921
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YB1921
3-Pin Microprocessor Reset Monitor
Electrical Characteristics
Vcc=5V for L/M/J; 3.3V for T/S; 3.0V for R, TA = 25°C, unless otherwise specified.
Parameter
Input Voltage
Supply Current
Symbol
VCC
ICC
Reset Threshold
VTH
Reset Threshold Temperature
Coefficient (4)
VCC to Reset Delay VCC = VTH to
(VTH – 100mV)
Reset Active Timeout Period
RESET Output Voltage Low
RESET Output Voltage High
VOL
VOH
Condition
YB1921L-4.63V
YB1921M-4.38V
YB1921J-4.00V
YB1921T-3.08V
YB1921S-2.93V
YB1921R-2.63V
Min
2.0
4.54
4.29
3.92
3.02
2.87
2.58
Typ
18
4.63
4.38
4.00
3.08
2.93
2.63
30
ISINK = 3mA
ISOURCE = 800μA
0.8VCC
20
240
Max
5.5
25
4.72
4.47
4.08
3.14
2.99
2.68
0.4
Unit
V
μA
V
ppm/°C
μsec
msec
V
V
Note 1: Exceeding the absolute maximum rating may damage the device.
Note 2: The device is not guaranteed to function outside its operating rating.
Note 3: The maximum allowable power dissipation at any TA (ambient temperature) is calculated using: PD (MAX) =
(TJ (MAX) – TA)/ΘJA. Exceeding the maximum allowable power dissipation will result in excessive die temperature, and the
regulator will go into thermal shutdown. See “Thermal Consideration” section for details
Note 4: RESET threshold temperature coefficient is the worst case voltage change divided by the total temperature
range.
YB1921
www.yobon.com.tw
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