Preliminary
RT9808
Micro-Power Voltage Detectors
General Description
The RT9808 is a micro-power voltage detector
supervising the power supply voltage level for
microprocessors (µP) or digital systems. It provides
internally fixed threshold levels with 0.1V per step
ranging from 1.5V to 5V, which covers most digital
applications. It features low supply current of 3µA.
The RT9808 performs supervisory function by
sending out a reset signal whenever the VDD voltage
falls below a preset threshold level. This reset signal
will last the whole period before VDD recovering.
Once VDD recovered up-crossing the threshold level,
the reset signal will be released if VDD is above
threshold and last for the whole period of reset active
time out.
RT9808 is n-channel, open-drain output.
Features
Internally Fixed Threshold 1.5V to 5V in 0.1V Step
±
2% Accuracy
Low Supply Current 3µA
µ
Quick Reset within 20µS
µ
Built-in Recovery Delay 200mS
Low Functional Supply Voltage 0.9V
N-Channel Open Drain Output
Small 3-Pin SOT-23/SOT89 and 5-Pin SOT-25
Packages
Pin Configurations
Part Number
RT9808-
CV
1
Pin Configurations
3
TOP VIEW
1. RESET
2. GND
3. VDD
TOP VIEW
1. RESET
2. VDD
3. GND
TOP VIEW
(Plastic SOT-23)
2
Applications
Computers
Controllers
Intelligent Instruments
Critical
µP
and
µC
Power Monitoring
Portable/Battery-Powered Equipment
RT9808-
CX
(Plastic SOT-89)
1
2
3
RT9808-
CB
5
4
(Plastic SOT-25)
Ordering Information
RT9808-
Package Type
V : SOT-23
X : SOT-89
B : SOT-25
Operating temperature range
C: Commercial standard
Reset Threshold
15 : 1.5V
16 : 1.6V
:
49 : 4.9V
50 : 5.0V
µP
RESET
1
2
3
1.
2.
3.
4.
5.
RESET
VDD
GND
NC
NC
Typical Application Circuit
VDD
Pull
100K
Up
RT9808
GND
VDD
RESET
DS9808-01 January 2002
www.richtek-ic.com.tw
1
RT9808
Pin Description
Pin Name
GND
RESET
VDD
NC
Pin Function
Ground Pin
Preliminary
Reset Pulse Output, Negative Pulse
Power Pin
No Connected
Function Block Diagram
VDD
VSET
CMP
TIMER
N
RESET
Threshold Voltage Setting
POR
Power On Reset
www.richtek-ic.com.tw
DS9808-01 January 2002
2
Preliminary
Absolute Maximum Ratings
Terminal Voltage (with Respect to GND)
VDD
All Other Inputs
Input Current, VDD
Output Current, RESET
Power Dissipation, P
D
@ T
A
= 25°C
SOT-23
SOT-89
SOT-25
Operating Junction Temperature Range
Storage Temperature Range
Package Thermal Resistance
SOT-23,
θ
JA
SOT-89,
θ
JC
SOT-89,
θ
JA
SOT-25,
θ
JA
Lead Temperature (Soldering, 5sec.)
RT9808
-0.3V to 6.0V
-0.3V to VDD+0.3V
20mA
20mA
0.25W
0.5W
0.25W
-40°C ~ 125°C
-65°C ~ 125°C
250°C /W
100°C /W
300°C /W
250°C /W
260°C
Electrical Characteristics
(VDD = 3.0, unless specified)
Parameter
Operating VDD (V
OUT
) Range
Supply Current
Reset Threshold
Threshold Voltage Accuracy
V
CC
Drop to Reset Delay
Reset Active Time Out Period
RESET Output Voltage
Note1: 1.5V ~ 5V, step 0.1V
Symbol
V
DD
I
DD
V
TH
∆V
TH
t
RD
t
RP
V
OL
V
DD
= 1.5V ~ 5V, I
OUT
= 0
T
A
= 27°C
T
A
= 27°C
Drop = -125mV
V
DD
≥
1.02×V
TH
V
DD
< V
TH
, I
SINK
> 3.5mA
Test Conditions
Min
0.9
--
--
--
--
--
--
Typ
--
3
Note1
--
--
200
0.4
Max
6
--
--
2
20
--
--
Units
V
µA
V
%
µS
mS
V
DS9808-01 January 2002
www.richtek-ic.com.tw
3
RT9808
Measuring Circuit
(1) Detection Voltage
Preliminary
(3) Output Transistor Current
V
DD
V
DD
V
RT9808
V
SS
R (100k
Ω
)
OUT
Oscilloscope
P.G
V
DD
RT9808
V
SS
100kΩ
OUT CRT
CL
6V
(2) Current Consumption
(4) Dynamic Response
A
V
DD
V
DD
V
DD
RT9808
V
SS
OUT
V
V
DD
RT9808
V
SS
OUT
V
A
V
DS
V
www.richtek-ic.com.tw
DS9808-01 January 2002
4
Preliminary
Typical Operating Characteristics
7
6
RT9808
Nch Driver Output Current vs. V
DS
1.7V
12
10
Nch Driver Output Current vs. V
DS
2.2V
2.0V
Output Current I
OUT
(mA)
5
4
3
2
1
0
0
0.5
1
1.5
2
Output Current I
OUT
(mA)
8
6
4
2
0
1.5V
1.5V
T
A
= 25°C
RT9808-20CV
2.5
3
T
A
= 25°C
RT9808-24CV
0
0.5
1
1.5
2
2.5
3
V
DS
(V)
V
DS
(V)
18
15
12
9
Nch Driver Output Current vs. V
DS
2.8V
36
30
Nch Driver Output Current vs. V
DS
4.0V
Output Current I
OUT
(mA)
Output Current I
OUT
(mA)
3.5V
24
3.0V
18
2.5V
12
2.0V
6
1.5V
0
2.0V
6
3
0
0
0.5
1
1.5
2
1.5V
T
A
= 25°C
RT9808-30CV
2.5
3
T
A
= 25°C
RT9808-45CV
2
3
4
0
1
V
DS
(V)
V
DS
(V)
Nch Driver output Current vs. V
DS
40
4.0V
3.5V
24
3.0V
16
2.5V
2.0V
1.5V
0
0
1
2
3
4.5V
Output Voltage vs. Input Voltage
7
T
A
= 25°C
6
Output Current I
OUT
(mA)
Output Voltage V
OUT
(V)
32
5.0V
5
4
3.0V
3
2
1
0
0.0
2.0V
2.4V
4.5V
8
T
A
= 25°C
RT9808-50CV
4
5
V
DS
(V)
1.0
2.0
3.0
4.0
5.0
6.0
Input Voltage V
IN
(V)
DS9808-01 January 2002
www.richtek-ic.com.tw
5
