Electronic Components Datasheet Search |
|
UCC1804L Datasheet(PDF) 5 Page - Texas Instruments |
|
UCC1804L Datasheet(HTML) 5 Page - Texas Instruments |
5 / 20 page 5 UCC1800/1/2/3/4/5 UCC2800/1/2/3/4/5 UCC3800/1/2/3/4/5 PIN DESCRIPTIONS COMP: COMP is the output of the error amplifier and the input of the PWM comparator. Unlike other devices, the error amplifier in the UCC3800 family is a true, low output-impedance, 2MHz operational amplifier. As such, the COMP terminal can both source and sink current. However, the error amplifier is internally current limited, so that you can command zero duty cycle by externally forcing COMP to GND. The UCC3800 family features built-in full cycle Soft Start. Soft Start is implemented as a clamp on the maximum COMP voltage. CS: CS is the input to the current sense comparators. The UCC3800 family has two different current sense comparators: the PWM comparator and an over-current comparator. The UCC3800 family contains digital current sense filter- ing, which disconnects the CS terminal from the current sense comparator during the 100ns interval immediately following the rising edge of the OUT pin. This digital filter- ing, also called leading-edge blanking, means that in most applications, no analog filtering (RC filter) is re- quired on CS. Compared to an external RC filter tech- nique, the leading-edge blanking provides a smaller effective CS to OUT propagation delay. Note, however, that the minimum non-zero On-Time of the OUT signal is directly affected by the leading-edge-blanking and the CS to OUT propagation delay. The over-current comparator is only intended for fault sensing, and exceeding the over-current threshold will cause a soft start cycle. FB: FB is the inverting input of the error amplifier. For best stability, keep FB lead length as short as possible and FB stray capacitance as small as possible. GND: GND is reference ground and power ground for all functions on this part. OUT: OUT is the output of a high-current power driver ca- pable of driving the gate of a power MOSFET with peak currents exceeding ± 750mA. OUT is actively held low when VCC is below the UVLO threshold. The high-current power driver consists of FET output de- vices, which can switch all of the way to GND and all of the way to VCC. The output stage also provides a very low impedance to overshoot and undershoot. This means that in many cases, external schottky clamp diodes are not required. RC: RC is the oscillator timing pin. For fixed frequency operation, set timing capacitor charging current by con- necting a resistor from REF to RC. Set frequency by con- necting a timing capacitor from RC to GND. For best performance, keep the timing capacitor lead to GND as short and direct as possible. If possible, use separate ground traces for the timing capacitor and all other func- tions. The frequency of oscillation can be estimated with the following equations: UCCx800/1/2/4: F RC = • 15 . UCCx803, UCCx805: F RC = • 10 . where frequency is in Hz, resistance is in ohms, and ca- pacitance is in farads. The recommended range of timing resistors is between 10k and 200k and timing capacitor is 100pF to 1000pF. Never use a timing resistor less than 10k. To prevent noise problems, bypass VCC to GND with a ceramic capacitor as close to the VCC pin as possible. An electrolytic capacitor may also be used in addition to the ceramic capacitor. REF: REF is the voltage reference for the error amplifier and also for many other functions on the IC. REF is also used as the logic power supply for high speed switching logic on the IC. When VCC is greater than 1V and less than the UVLO threshold, REF is pulled to ground through a 5k ohm re- sistor. This means that REF can be used as a logic out- put indicating power system status. It is important for reference stability that REF is bypassed to GND with a ceramic capacitor as close to the pin as possible. An electrolytic capacitor may also be used in addition to the ceramic capacitor. A minimum of 0.1 µF ceramic is re- quired. Additional REF bypassing is required for external loads greater than 2.5mA on the reference. To prevent noise problems with high speed switching transients, bypass REF to ground with a ceramic capaci- tor very close to the IC package. VCC: VCC is the power input connection for this device. In normal operation VCC is powered through a current limiting resistor. Although quiescent VCC current is very low, total supply current will be higher, depending on OUT current. Total VCC current is the sum of quiescent VCC current and the average OUT current. Knowing the operating frequency and the MOSFET gate charge (Qg), average OUT current can be calculated from: IQ F OUT g =× . There should be a minimum of 1.0 mF in parallel with a 0.1 mF ceramic capacitor from VCC to ground located close to the device |
Similar Part No. - UCC1804L |
|
Similar Description - UCC1804L |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.NET |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | 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 |