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PDF RT9807 Data sheet ( Hoja de datos )
| Número de pieza | RT9807 | |
| Descripción | Micro-Power Voltage Detector | |
| Fabricantes | Richtek Technology Corporation | |
| Logotipo |  |
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RT9807
Micro-Power Voltage Detector with Manual Reset
General Description
The RT9807 is a micro-power voltage detector with
deglitched manual reset input which supervises the power
supply voltage level for microprocessors (μP) or digital
systems. It provides internally fixed threshold levels
ranging from 1.2V to 3.3V with 0.1V per step, which covers
most digital applications. It features low supply current of
3μA.
The RT9807 performs supervisory function by sending out
a reset signal whenever the VDD voltage falls below a
preset threshold level. The timeout period of this reset
signal can be adjusted via an external capacitor. Once
VDD recovers above the threshold level, the reset signal
will be released after a certain delay time. To manually
pull reset signal low, just pull the manual reset input (MR)
below the specified logic-low level.
The RT9807 is available in an SOT-23-5 package.
Features
z Monitor System Voltages from 0.9V to 5.5V
z Capacitor-Adjustable Reset Timeout Period
z Manual Reset Input
z Low Quiescent Current
z High Accuracy ±1.5%
z Low Functional Supply Voltage 0.9V
z N-Channel Open-Drain Output
z Small SOT-23-5 Package
z RoHS Compliant and Halogen Free
Applications
z Computers
z Controllers
z Intelligent Instruments
z Critical uP and uC Power Monitoring
z Portable/Battery-Powered Equipment
Ordering Information
RT9807-
Package Type
B : SOT-23-5
Pin Configurations
(TOP VIEW)
VDD
CT
54
Lead Plating System
G : Green (Halogen Free and Pb Free)
23
Output Voltage
12 : 1.2V
13 : 1.3V
RST GND MR
SOT-23-5
Note :
:
32 : 3.2V
33 : 3.3V
Typical Application Circuit
R
470k
Richtek products are :
`RoHS compliant and compatible with the current require-
ments of IPC/JEDEC J-STD-020.
VDD
5
CIN
RT9807
VDD
RST
1
1uF
Reset
`Suitable for use in SnPb or Pb-free soldering processes.
Marking Information
3 MR GND CT 4
2
CCT
10nF
For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area.
DS9807-01 April 2011
www.richtek.com
1
1 page  
RT9807
Application Information
The RT9807 provides adjustable reset delay time to fit
the need of a variety of μP applications. The reset delay
time of the RT9807 can be adjusted by connecting a
capacitor between the CT pin and GND. The CT capacitor
must fit the need of low-leakage (<10nA), and it is
recommended to use a ceramic capacitor such as X7R or
NPO type.
VCC
R
R1 RT9807
VDD
RST
R1
GND
CT
CCT
Reset Delay Time Setting
When the VDD voltage exceeds the VDD threshold voltage,
a current source will start to charge the CT capacitor and
the CT voltage will rise. When the CT voltage exceeds
0.65V, the RST voltage will change from low to high.
Therefore, there is a delay time between the point of VDD
reaching its threshold voltage and the RST active-high
point. The delay time can be calculated according to the
following equation.
tDELAY (μs) =
0.58
0.18 x 106 x CCT (μF)
+ 220
VDD Voltage
VCT
VDD Threshold
Voltage
GND
0.65V
GND
RST Voltage
GND
Delay Time
Figure 1. Delay Time
Operating with a Voltage Divider
The voltage detector monitors the VCC voltage to generate
a reset signal when VCC is higher than the detecting level.
The detecting level is determined by an external resistive
voltage divider.
VCC_TH = VTH x
⎛⎜⎝1 +
R1
R2
⎞
⎟⎠
,
VTH
:
Threshold
Voltage.
VCC_HYS = VHYS x
⎛⎜⎝1 +
R1 ⎞
R2 ⎟⎠
DS9807-01 April 2011
Figure 2. Voltage Divider
The rising and falling of the VCC and RST voltage can be
explained in five steps as shown in the following diagram.
12
34
5
VCC A
Hysteresis
range
B
VCC_TH
VCC_TH – Hysteresis Voltage
Minimum Operation Voltage
GND
RST Voltage
Power-On Reset
Delay Time
GND
Drop Reset
Delay Time
Figure 3. Operation Diagram
1. RST voltage is pulled up to VCC voltage.
2. When the VCC voltage is down to the detector threshold
voltage (Point A), RST voltage becomes low level.
3. When the VCC voltage is lower than minimum operating
voltage, the RST voltage is indefinite. In the case of
open drain type, RST voltage is equal to pull-up voltage.
4. RST voltage becomes low level.
5. When the VCC voltage exceeds the threshold voltage
(Point B), the internal source current will start to charge
CT capacitor. The RST voltage will go high after a delay
time when the CT capacitor voltage reaches 0.65V.
www.richtek.com
5
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| PDF Descargar | [ Datasheet RT9807.PDF ] | |
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