Voltage generator with standby operating mode

Details Voltage generator with standby operating mode Voltage generator with standby operating mode

2002-03-04

2003-05-27

Sterrett, Jeffrey (Department: 2838)

Electricity: power supply or regulation systems

Output level responsive

Using a three or more terminal semiconductive device as the...

Reexamination Certificate

active

06570367

ABSTRACT:

BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a voltage generator that can be operated in a normal operating mode and in a standby operating mode. In addition, the invention relates to a method for operating such a voltage generator.
Voltage generators are used in integrated circuits in order to produce an internal supply voltage on a semiconductor chip, from an externally supplied supply voltage. The internal supply voltage is adapted to the requirements of the internal functional units of the integrated circuit. Thus, voltages can be produced whose magnitude deviates from the magnitude of the externally supplied voltage. The internal voltage can be higher or lower than the externally supplied voltage. Moreover, the voltage regulator for the internally supplied voltage ensures that a sufficiently constant voltage is produced independently of fluctuations of the externally supplied supply voltage, and as much as possible, also independently of the load that will be driven internally. The voltage generators consume dissipated power. Voltage generators are therefore designed for a normal operation in which a high drive capability is achieved and the power dissipation is high, and in addition for a standby operation in which the voltage generator has a low drive capability and the power dissipation is low.
In standby operation, only selected functional units of the integrated circuit are switched on. The circuit in standby operating mode can be activated to switch over from standby operation to normal operation. Correspondingly, the voltage generator also switches over from its standby operating mode, in which the dissipated power loss is low, into a normal operation, which consumes a higher dissipated power.
A conventional voltage generator with a standby operating mode and a normal operating mode is shown in FIG.
1
. The voltage generator in
FIG. 1
has a voltage generator
10
for standby operation and a voltage generator
20
for normal operation. Generator
10
is always switched on, both in standby operation and also in normal operation. Generator
10
has a low dissipated power loss. Generator
20
is also connected in normal operation, produces an output voltage with a high drive capability, and correspondingly has a high dissipated power loss. The output terminal connections of generators
10
,
20
are coupled with one another. External supply voltage VEXT is supplied to generators
10
and
20
. Generators
10
and
20
generate the regulated internal voltage VINT from the external supply voltage VEXT and provide the regulated internal voltage VINT at the output terminal connection
42
.
Both voltage generators
10
,
20
have a circuit design that is identical in principle. A differential amplifier
11
or
21
is supplied with power by the external supply voltage VEXT, and compares a reference voltage VREF with the voltage VINT that is produced at the output. The gate of a current source transistor
12
or
22
is driven in dependence upon the comparison. The drain-source current path of current source transistor
12
or
22
is connected between a terminal for receiving the external supply voltage VEXT and the output terminal
42
providing the internal supply voltage VINT. It is noted that corresponding inputs of the differential amplifiers
11
or
21
are driven by the same reference signal VREF.
In comparison to the always-active standby voltage generator
10
, voltage generator
20
, which is active only in normal operation, has a switching device
23
through which the differential amplifier
21
can be switched on and off. The switching device
23
switches the voltage generator
20
on in normal operation when higher driving power is required. This state is communicated to the voltage generator by the received signal ACTIVE. Moreover, the voltage generator
20
is activated only if it has been ensured that a sufficiently high supply voltage is applied, known as the power-on state. This is communicated to the voltage generator
20
by the signal PWRON, which is combined with the signal ACTIVE through a logical AND operation. The logical combination of the signal ACTIVE with the signal PWRON prevents generator
20
from being activated too early. In principle, it can also be omitted.
The different current driving capacity of the voltage generators
10
,
20
is obtained by providing transistor
22
with a channel that is wider, for example, by a factor of n than the channel of transistor
12
. Likewise, the differential amplifier
21
includes transistors that are dimensioned larger by a factor of n than corresponding transistors in the differential amplifier
11
.
It is problematic that the circuit supplied by the voltage generator shown in
FIG. 1
can assume states in which a high current is drawn from the voltage generator when the signal ACTIVE does not indicate normal operation. This error situation can arise in particular if there are complex functional units that are driven. If in such a case, only the standby voltage generator
10
with a low driving power is switched on, but not voltage generator
20
for supplying high driving power, then the internal voltage can break down because the standby voltage generator
10
cannot provide sufficient current. In this state, the integrated circuit can block, which requires the external supply voltage to be switched off and a renewed startup to be performed in order to remove the error situation. The functional capacity and the functional reliability of the overall system is then adversely affected, so that such an error situation should be avoided to the greatest possible extent.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a voltage generator that has both a standby and a normal operating mode and which overcomes the above-mentioned disadvantages of the prior art apparatus of this general type.
In particular, it is an object of the invention to provide a voltage generator that has both a standby and a normal operating mode, and that operates in a functionally reliable manner.
With the foregoing and other objects in view there is provided, in accordance with the invention, a voltage generator that includes: an output connection for providing an output voltage; an input connection for receiving a first reference potential; and a first voltage regulator having an output stage and a comparator stage for driving the output stage. The output stage has an output connected to the output connection. The comparator stage has an input connected to the input connection for receiving the first reference potential and has another input connected to the output stage. The voltage generator also includes a second voltage regulator having an output stage, a comparator stage for driving the output stage, and a switch. The output stage has an output connected to the output connection. The comparator stage of the second voltage regulator has an input connected to the input connection for receiving the first reference potential and has another input connected to the output stage. The switch is for switching the second voltage regulator on and off. The voltage generator includes a connection for receiving a second reference potential that is different than the first reference potential. The voltage generator also includes an additional comparator stage having a first input connected to the connection for receiving the second reference potential. The additional comparator stage has a second input connected to the output connection. The additional comparator stage has an output providing an output signal for controlling the switch of the second voltage regulator.
In accordance with an added feature of the invention, there is provided a voltage divider having an input connected to the input connection for receiving the first reference potential. The voltage divider has an output connected to the connection for receiving the second reference potential.
In accordance with an additional feature of the invention, there is provided a further connection for receiving a re

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