Electronic Components Datasheet Search |
|
LTC2912HTS8-2 Datasheet(PDF) 9 Page - Linear Technology |
|
LTC2912HTS8-2 Datasheet(HTML) 9 Page - Linear Technology |
9 / 12 page LTC2912 9 2912fa APPLICATIONS INFORMATION When the VH input drops below its designed threshold, the UV pin asserts low. When the input recovers above its designed threshold, the UV output timer starts. If the input remains above the designed threshold when the timer finishes, the UV pin weakly pulls high. However, if the input falls below its designed threshold during this timeout period, the timer resets and restarts when the input is above the designed threshold. The OV and OV outputs behave as the UV output when LATCH is high (LTC2912-1, LTC2912-3). Selecting the UV/OV Timing Capacitor The UV and OV timeout period (tUOTO) for the LTC2912 is adjustable to accommodate a variety of applications. Connecting a capacitor, CTMR, between the TMR pin and ground sets the timeout period. The value of capacitor needed for a particular timeout period is: CTMR = tUOTO • 115 • 10–9 [F/s] The Reset Timeout Period vs Capacitance graph found in the Typical Performance Characteristics shows the desired delay time as a function of the value of the timer capacitor that must be used. The TMR pin must have a minimum 10pF load or be tied to VCC. For long timeout periods, the only limitation is the availability of a large value capaci- tor with low leakage. Capacitor leakage current must not exceed the minimum TMR charging current of 1.3μA.Tying the TMR pin to VCC bypasses the timeout period. Undervoltage Lockout When VCC falls below 2V, the LTC2912 asserts an undervoltage lockout (UVLO) condition. During UVLO, UV is asserted and pulled low while OV and OV are cleared and blocked from asserting. When VCC rises above 2V, UV follows the same timing procedure as an undervoltage condition on the VH input. Shunt Regulator The LTC2912 has an internal shunt regulator. The VCC pin operates as a direct supply input for voltages up to 6V. Under this condition, the quiescent current of the device remains below a maximum of 70μA. For VCC voltages higher than 6V, the device operates as a shunt regulator and should have a resistance RZ between the supply and the VCC pin to limit the current to no greater than 10mA. When choosing this resistance value, select an appropriate location on the I-V curve shown in the Typical Performance Characteristics to accommodate any variations in VCC due to changes in current through RZ. UV, OV and OV Output Characteristics The DC characteristics of the UV, OV and 0V pull-up and pull-down strength are shown in the Typical Performance Characteristics. Each pin has a weak internal pull-up to VCC and a strong pull-down to ground. This arrangement allows these pins to have open-drain behavior while pos- sessing several other beneficial characteristics. The weak pull-up eliminates the need for an external pull-up resistor when the rise time on the pin is not critical. On the other hand, the open-drain configuration allows for wired-OR connections, and is useful when more than one signal needs to pull down on the output. VCC of 1V guarantees a maximum VOL = 0.15V at UV. At VCC = 1V, the weak pull-up current on OV is barely turned on. Therefore, an external pull-up resistor of no more than 100k is recommended on the OV pin if the state and pull-up strength of the OV pin is crucial at very low VCC. Note however, by adding an external pull-up resistor, the pull-up strength on the OV pin is increased. Therefore, if it is connected in a wired-OR connection, the pull-down strength of any single device must accommodate this additional pull-up strength. Output Rise and Fall Time Estimation The UV, OV and OV outputs have strong pull-down capa- bility. The following formula estimates the output fall time (90% to 10%) for a particular external load capacitance (CLOAD): tFALL ≈ 2.2 • RPD • CLOAD where RPD is the on-resistance of the internal pull-down transistor, typically 50Ω at VCC > 1V and at room tem- perature (25°C). CLOAD is the external load capacitance on the pin. Assuming a 150pF load capacitance, the fall time is 16.5ns. |
Similar Part No. - LTC2912HTS8-2 |
|
Similar Description - LTC2912HTS8-2 |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.COM |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |