US 11,835,557 B2
Frequency detection circuit
Dae-Ho Yun, Gyeonggi-do (KR); and Seong-Jin Kim, Gyeonggi-do (KR)
Assigned to SK hynix Inc., Seoul (KR)
Filed by SK hynix Inc., Gyeonggi-do (KR)
Filed on Oct. 25, 2019, as Appl. No. 16/663,829.
Claims priority of application No. 10-2018-0130650 (KR), filed on Oct. 30, 2018.
Prior Publication US 2020/0132743 A1, Apr. 30, 2020
Int. Cl. G01R 23/165 (2006.01); H03H 11/04 (2006.01)
CPC G01R 23/165 (2013.01) [H03H 11/04 (2013.01)] 10 Claims
OG exemplary drawing
 
1. A frequency detection circuit comprising:
a pulse generator configured to generate a pulse signal having a pulse width proportional to a cycle of a periodic wave whose frequency is to be measured;
a first low pass filter configured to selectively allow the pulse signal to pass therethrough, and have a first cutoff frequency;
a second low pass filter configured to selectively allow the pulse signal to pass therethrough, and have a second cutoff frequency different from the first cutoff frequency; and
a determination circuit configured to generate plural frequency detection signals based on a first pulse signal having passed through the first low pass filter and a second pulse signal having passed through the second low pass filter,
wherein the determination circuit generates a first frequency detection signal by detecting activation or deactivation of the first pulse signal, and generates a second frequency detection signal by detecting activation or deactivation of the second pulse signal,
wherein when the first frequency detection signal and the second frequency detection signal are activated, it is determined that a frequency of the periodic wave is low,
wherein when the first frequency detection signal is activated and of the second frequency detection signal is deactivated, it is determined that the frequency of the periodic wave is intermediate, wherein when the first frequency detection signal and the second frequency detection signal are deactivated it is determined that the frequency of the periodic wave is high,
wherein the first low pass filter and the second low pass filter are filters that blocks a pulse signal having a high frequency and allow a pulse signal having a low frequency to pass therethrough,
wherein when the periodic wave is a high frequency, the pulse signal does not reach a logic high level by the first low pass filter and the second low pass filter so that the frequency detection signal is deactivated, and
wherein when the periodic wave is a low frequency, the pulse signal reaches a logic high level by the first low pass filter and the second low pass filter so that the frequency detection signal is activated.