Semiconductor device including driver circuit for adjusting duty ratio
A semiconductor device includes a first pull-up circuit connected between a first power node supplying a first power voltage and an output node through which a signal is output, and including a plurality of NMOS transistors; a second pull-up circuit connected in parallel to the first pull-up circuit between the first power node and the output node and including a plurality of PMOS transistors; and a control circuit outputting a first pull-up code to the first pull-up circuit and outputting the second pull-up code to the second pull-up circuit. In a first operating mode, the signal swings between a first low level lower than the first power voltage, and a first high level lower than ½ times the first power voltage, resistance of the first pull-up circuit is determined based on the first pull-up code, and resistance of the second pull-up circuit is determined based on the second pull-up code.
1 . A semiconductor device comprising:
a pull-up circuit connected between a first power node supplying a first power voltage and an output node through which a signal is output;
a pull-down circuit connected between a second power node supplying a second power voltage, lower than the first power voltage, and the output node; and
a control circuit configured to control the pull-up circuit and the pull-down circuit,
wherein the pull-up circuit includes:
a first pull-up circuit including a plurality of NMOS transistors connected between the first power node and the output node, and
a second pull-up circuit including a plurality of PMOS transistors connected between the first power node and the output node, and
wherein, in a first operating mode of the semiconductor device:
the signal swings between a first low level, corresponding to the second power voltage, and a first high level lower than the first power voltage,
the control circuit is configured to output a first pull-up code to the first pull-up circuit, and output a second pull-up code to the second pull-up circuit,
at least one of the plurality of PMOS transistors of the second pull-up circuit is configured to turn on based on the second pull-up code,
a first time period for the control circuit to input the first pull-up code to the first pull-up circuit is longer than a second time period for the control circuit to input the second pull-up code to the second pull-up circuit,
the first pull-up circuit is configured to activate in response to the first pull-up code in the first time period, and
the second pull-up circuit is configured to activate in response to the second pull-up code in the second time period.
2 . The semiconductor device of claim 1 , wherein, in the first operation mode, the semiconductor device is configured such that the control circuit:
adjusts the second pull-up code to decrease resistance of the second pull-up circuit when a duty ratio of the signal is less than 50%, and
adjusts the second pull-up code to increase resistance of the second pull-up circuit when a duty ratio of the signal is greater than 50%.
3 . The semiconductor device of claim 2 , wherein the control circuit is configured to:
decrease a value of the second pull-up code when the duty ratio of the signal is lower than 50%, and
increase a value of the second pull-up code when the duty ratio of the signal is higher than 50%.
4 . The semiconductor device of claim 1 , wherein a time period at which the control circuit outputs the second pull-up code to the second pull-up circuit overlaps a rising period of the signal.
5 . The semiconductor device of claim 1 , wherein the number of bits of the first pull-up code is equal to the number of bits of the second pull-up code.
6 . The semiconductor device of claim 1 , wherein, in a second operating mode of the semiconductor device:
the signal swings between a second low level higher than the second power voltage, and a second high level lower than the first power voltage, and
the control circuit is configured to output a fixed code to the second pull-up circuit.
7 . The semiconductor device of claim 6 , wherein the second low level is equal to the first high level.
8 . The semiconductor device of claim 1 , wherein the first high level is ⅓ times the first power voltage.
9 . The semiconductor device of claim 1 , wherein the control circuit includes:
a buffer including a first input terminal configured to receive the signal, a second input terminal configured to receive a complementary signal complementary to the signal, and an output terminal configured to output an output signal,
a charge pump circuit configured to perform a charging operation or a discharging operation in response to the output signal of the buffer,
a comparator configured to compare an output voltage of the charge pump circuit with a reference voltage, and
a counter configured to output the second pull-up code based on a comparison result of the comparator.
10 . The semiconductor device of claim 9 , wherein the output signal of the buffer is a digital signal swinging between a ground voltage and a power voltage, and
wherein a level of the reference voltage is ½ times a level of the power voltage.
11 . A semiconductor device comprising:
a first driver circuit including a pull-up circuit and a pull-down circuit, and configured to output a first signal to a first pad;
a second driver circuit including a pull-up circuit and a pull-down circuit, and configured to output a second signal, complementary to the first signal, to a second pad different from the first pad; and
a control circuit configured to control the first driver circuit and the second driver circuit,
wherein the control circuit includes:
a buffer including input terminals connected to the first pad and the second pad and an output terminal configured to output a digital signal based on a difference between the first signal and the second signal,
an integrator configured to operate in response to the digital signal,
a comparator configured to compare an output voltage of the integrator with a reference voltage, and
a counter configured to output an N-bit code based on a comparison result of the comparator, N being a natural number equal to or greater than 2,
wherein resistance of the pull-up circuit of the first driver circuit and resistance of the pull-up circuit of the second driver circuit are adjusted based on the N-bit code.
12 . The semiconductor device of claim 11 , wherein the integrator includes a plurality of pumping capacitors configured to be charged or discharged based on the digital signal.
13 . The semiconductor device of claim 11 , wherein, when the output voltage of the integrator is higher than the reference voltage, the semiconductor device is configured such that the counter outputs the N-bit code to increase the resistance of the pull-up circuit of each of the first driver circuit and the second driver circuit.
14 . The semiconductor device of claim 11 , wherein, when the output voltage of the integrator is lower than the reference voltage, the semiconductor device is configured such that the counter outputs the N-bit code to decrease the resistance of the pull-up circuit of each of the first driver circuit and the second driver circuit.
15 . The semiconductor device of claim 11 , wherein the buffer is a fully differential amplifier.
16 . The semiconductor device of claim 11 , wherein the pull-up circuit of each of the first driver circuit and the second driver circuit includes a first pull-up circuit including a plurality of NMOS transistors and a second pull-up circuit including a plurality of PMOS transistors,
wherein the first pull-up circuit and the second pull-up circuit of each of the first driver circuit and the second driver circuit are respectively connected in parallel to each other, and
wherein the N-bit code is input to the second pull-up circuit of each of the first driver circuit and the second driver circuit.
17 . The semiconductor device of claim 16 , wherein the control circuit is configured to output a code determined in a ZQ calibration operation of the semiconductor device to the first pull-up circuit of each of the first driver circuit and the second driver circuit.
18 . A semiconductor device comprising:
a pull-up circuit including:
a first pull-up circuit connected between a first power node supplying a first power voltage and an output node through which a signal is output, and including a plurality of NMOS transistors, and
a second pull-up circuit connected in parallel to the first pull-up circuit between the first power node and the output node and including a plurality of PMOS transistors; and
a control circuit configured to output a first pull-up code to the first pull-up circuit and output a second pull-up code to the second pull-up circuit,
wherein, in a first operating mode of the semiconductor device:
the signal swings between a first low level corresponding to a second power voltage, lower than the first power voltage, and a first high level, lower than ½ times the first power voltage,
resistance of the first pull-up circuit is determined based on the first pull-up code, and resistance of the second pull-up circuit is determined based on the second pull-up code,
total resistance of the pull-up circuit is less than the resistance of the first pull-up circuit and the resistance of the second pull-up circuit, and
the first high level is the maximum voltage level of the signal.
19 . The semiconductor device of claim 18 , further comprising:
a pull-down circuit connected between a second power node supplying the second power voltage and the output node and including a plurality of NMOS transistors.