Internal voltage fall-down circuit

Details Internal voltage fall-down circuit Internal voltage fall-down circuit

1999-06-29

2001-05-29

Cunningham, Terry D. (Department: 2816)

Miscellaneous active electrical nonlinear devices, circuits, and

Specific identifiable device, circuit, or system

With specific source of supply or bias voltage

C323S316000

Reexamination Certificate

active

06239652

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an internal voltage fall-down circuit of a semiconductor device. In particular, the present invention relates to an internal voltage fall-down circuit which can test fuse programs for controlling an internal power supply voltage by pad signals without fuse blowing.
2. Description of the Prior Art
A conventional internal voltage fall-down circuit includes a reference voltage generating section
10
, a reference voltage transforming section
20
and a driver section
30
, as shown in
FIG. 1
, wherein an output signal Vint from the conventional internal voltage fall-down circuit is input to an internal circuit
40
as supply voltage. An output signal VR
2
from the reference voltage generating section
10
is input to a first input terminal of a first comparator
21
in the reference voltage transforming section
20
, and an output signal VR from the reference voltage transforming section
20
is used as a final comparison voltage of the driver section
30
.
A reference voltage generator
11
in the reference voltage generating section
10
outputs a stabilized voltage VR
1
regardless of external voltage fluctuations. Common types of it are a bandgap reference voltage generator or Windler current source. The output voltage VR
1
from the reference voltage generator
11
is input to the first input terminal of the first comparator
12
in the voltage amplifier
16
. Then an output voltage VR
2
from the reference voltage generator
16
is divided into a given voltage Va by a voltage divider consisted of fixed resistors
14
,
15
, which is then input to the second input terminal of the first comparator
12
. A fallen reference voltage VR
2
is then output from a first current driver
13
connected to the output terminal of the first comparator
12
.
The resistor
15
is a fixed resistor to provide a single resistance value corresponding to fuse programs.
The reference voltage transforming section
20
performs a normal mode and a stress mode operation and then outputs an output voltage in a normal mode operation, wherein the reference voltage VR
2
from the reference voltage generating section
10
is input to the first input terminal of a second comparator
21
used in a normal mode operation, the output voltage VR is feedbacked to the second input terminal of the second comparator
21
thereof, and the second current driver
22
is connected to the output terminal of the second comparator
21
thereof.
The reference voltage transforming section
20
outputs the output voltage VR in a stress mode operation, wherein a bias voltage VST from a bias circuit
23
is input to the first input terminal of a third comparator
24
used in a stress mode operation, the output voltage VR is feedbacked to the second input terminal of the third comparator
24
thereof and a third current driver
25
is connected to the output terminal of the third comparator
24
thereof.
Here, the term “a normal mode operation” means that “supply voltage=3.3V±10% and the term “a stress mode operation” means that “supply voltage is more than 1.5×3.3V”.
In addition, in a normal mode operation, since the second current driver
22
is enabled by the second comparator
21
and the third current driver
25
is enabled by the third comparator
24
, the resulting output voltage VR holds the reference voltage VR
2
from the reference voltage generating section
10
. In a stress mode operation, since the second current driver
22
is enabled by the second comparator
21
and the third current driver
25
is enabled by the third comparator
24
, the resulting output voltage VR holds the bias voltage VST from the bias circuit
23
. Meanwhile, as the node onto which the bias voltage will be carried is connected to the bias circuit
23
and the fall-down current sink
27
, the bias voltage VST keeps “supply voltage-nVt(n=2)”.
The driver section
30
is used to provide current corresponding to each state of operation in the internal circuit
40
. However, when the supply voltage is turned on, the driver section
30
may be consisted of standby drivers
31
,
32
and
35
, and activation drivers
33
,
34
which are activated by an enable clock ACT only during an active mode. The standby drivers
31
,
32
and
35
has a structure of voltage follower type, in which the fall-down current sink
35
is connected to the node for outputting the internal supply voltage Vint from the internal circuit
40
and a ground voltage terminal. The activation drivers
33
,
34
are also voltage follower types.
The internal circuit
40
may be an on-chip circuit which employs the internal supply voltage Vint, a given value of which is fallen down, from an external supply voltage.
Normally, in the above-mentioned internal voltage fall-down circuit, variations in processes or noises occurring during operation of the on-chip circuit may cause the internal supply voltage levels to fluctuate. Accordingly, in order to compensate for the fluctuations in the internal supply voltage level, it is preferred that the above reference voltage VR
2
is controlled using a fuse program, when the reference voltage of the comparator for driving the final current driver.
Here, the variations in processes mean threshold voltage Vt or saturation current Ids. The noises occurring during operation of the on-chip circuit mean current spikes which cause a large current flow at a sensing or an input/output circuit, noise of which affects the internal circuit to cause change of preset voltage (i.e., change in potentials of the reference voltage).
Accordingly, the above-mentioned conventional internal voltage fall-down circuit has problems that it could compensate for the level changes in or test the reference voltage VR
2
from the reference voltage generating section
10
, and could measure information for fuse blowing, only after programming of the fuses built in the resistor
15
of the reference voltage generating section
10
is performed.
SUMMARY OF THE INVENTION
It is an object of the present invention to solve the problems involved in the prior art, and to provide an internal voltage fall-down circuit which is capable of previously measuring the potential of an internal supply voltage being the final output by changing a previously fuse-programmed reference voltage before the fuse blowing, and then of providing a fuse blowing information, when performing a fuse programming to set the potential of the optimum internal supply voltage.
To achieve the above object, the internal voltage fall-down circuit according to a preferred embodiment of the present invention is characterized by comprising:
a reference voltage generating section for variably generating an optimum reference voltage level of which is compensated for depending on changes in the preset reference voltage before fuse blowing;
a reference voltage transforming section for receiving the reference voltage from the reference voltage generating section and transforming the reference voltage into voltage for a normal mode or a stress mode which are presently set; and
a driver section for providing the signal from the reference voltage transforming section to an internal circuit as an internal supply voltage.


REFERENCES:
patent: 5254883 (1993-10-01), Horowitz et al.
patent: 5335203 (1994-08-01), Ishii et al.
patent: 5467052 (1995-11-01), Tsukada
patent: 5485117 (1996-01-01), Furumochi
patent: 5506541 (1996-04-01), Herndon
patent: 5661683 (1997-08-01), Song
patent: 5689460 (1997-11-01), Ooishi
patent: 5875145 (1999-02-01), Yamasaki et al.
patent: 62-165962 (1987-07-01), None

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