HT70XX
HT7050A
Symbol
Parameter
Hi®Lo Detectable Voltage
Lo®Hi Detectable Voltage
V
HYS
I
DD
V
DD
I
OL
D
V
DET
D
T
a
HT7070A
Symbol
Parameter
Hi®Lo Detectable Voltage
Lo®Hi Detectable Voltage
V
HYS
I
DD
V
DD
I
OL
D
V
DET
D
T
a
Hysteresis Width
Operating Current
Operating Voltage
Output Sink Current
Temperature Coefficient
Test Conditions
V
DD
¾
¾
¾
8V
¾
5V
¾
No load
¾
V
OUT
=0.5V
0°C<Ta<70°C
Conditions
¾
¾
¾
Min.
6.65
6.783
0.02
V
DET
¾
2.1
5
¾
Typ.
7
7.35
0.05
V
DET
4
¾
10
±0.9
Max.
7.35
8.085
0.1
V
DET
7
24
¾
¾
Hysteresis Width
Operating Current
Operating Voltage
Output Sink Current
Temperature Coefficient
Test Conditions
V
DD
¾
¾
¾
8V
¾
3.6V
¾
No load
¾
V
OUT
=0.36V
0°C<Ta<70°C
Conditions
¾
¾
¾
Min.
4.75
4.845
0.02
V
DET
¾
2.1
3
¾
Typ.
5
5.25
0.05
V
DET
4
¾
6
±0.9
Max.
5.25
5.775
0.1
V
DET
7
24
¾
¾
Ta=25°C
Unit
V
V
V
mA
V
mA
mV/°C
V
DET
Ta=25°C
Unit
V
V
V
mA
V
mA
mV/°C
V
DET
Functional Description
The HT70XX series is a set of voltage detectors
equipped with a high stability voltage reference which is
connected to the negative input of a comparator¾ de-
noted as V
REF
in the following figure for NMOS output
voltage detector.
When the voltage drop to the positive input of the com-
parator (i,e,V
B
) is higher than V
REF
, VOUT goes high,
M1 turns off, and V
B
is expressed as V
BH
=V
DD
´
(R
B
+R
C
) / (R
A
+R
B
+R
C
). If V
DD
is decreased so that V
B
falls to a value less than V
REF
, the comparator output in-
verts from high to low, V
OUT
goes low, V
C
is high, M1
turns on, RC is bypassed, and V
B
becomes:
V
BL
=V
DD
´R
B
/ (R
A
+R
B
), which is less than V
BH.
By so
doing, the comparator output will stay low to prevent the
circuit from oscillating when V
B
»
V
REF.
If V
DD
falls below the minimum operating voltage, the
output becomes undefined. When VDD goes from low to
V
DD
´
R
B
/ (R
A
+R
B
) > V
REF
, the comparator output and
V
OUT
goes high.
The detectable voltage is defined as:
V
DET
(-) =
R
A
+
R
B
+
R
C
´
V
REF
R
B
+
R
C
R
A
+
R
B
´
V
REF
R
B
The release voltage is defined as:
V
DET
(+) =
Rev. 1.60
6
January 14, 2003
HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
