Electronic Components Datasheet Search |
|
UCC1808-X Datasheet(PDF) 4 Page - Texas Instruments |
|
UCC1808-X Datasheet(HTML) 4 Page - Texas Instruments |
4 / 7 page 4 UCC1808-1/-2 UCC2808-1/-2 UCC3808-1/-2 f RC OSCILLATOR = 141 . where frequency is in Hertz, resistance in Ohms, and ca- pacitance in Farads. The recommended range of timing resistors is between 10k Ω and 200kΩ and range of tim- ing capacitors is between 100pF and 1000pF. Timing re- sistors less than 10k Ω should be avoided. For best performance, keep the timing capacitor lead to GND as short as possible, the timing resistor lead from VDD as short as possible, and the leads between timing components and RC as short as possible. Separate ground and VDD traces to the external timing network are encouraged. VDD: The power input connection for this device. Al- though quiescent VDD current is very low, total supply current will be higher, depending on OUTA and OUTB current, and the programmed oscillator frequency. Total VDD current is the sum of quiescent VDD current and the average OUT current. Knowing the operating fre- quency and the MOSFET gate charge (Qg), average OUT current can be calculated from IOUT = Qg • F, where F is frequency. To prevent noise problems, bypass VDD to GND with a ceramic capacitor as close to the chip as possible along with an electrolytic capacitor. A 1 µF decoupling capacitor is recommended. PIN DESCRIPTIONS (cont.) The oscillator generates a sawtooth waveform on RC. During the RC rise time, the output stages alternate on time, but both stages are off during the RC fall time. The output stages switch a ½ the oscillator frequency, with guaranteed duty cycle of < 50% for both outputs. Figure 1. Block diagram for oscillator. UDG-97009 A 200kHz push-pull application circuit with a full wave rec- tifier is shown in Fig. 2. The output, VO, provides 5V at 75W maximum and is electrically isolated from the input. Since the UCC3808 is a peak current mode controller the 2N2222A emitter following amplifier (buffers the CT wave- form) provides slope compensation which is necessary for duty ratios greater than 50%. Capacitor decoupling is very important with a single ground IC controller and a 1 µF is suggested as close to the IC as possible. The con- troller supply is a series RC for startup, paralleled with a bias winding on the output inductor used in steady state operation. Isolation is provided by an optocoupler with regulation done on the secondary side using the UC3965 Precision Reference with Low Offset Error Amplifier. Small signal compensation with tight voltage regulation is achieved using this part on the secondary side. Many choices ex- ist for the output inductor depending on cost, volume, and mechanically strength. Several design options are iron powder, molypermalloy (MPP), or a ferrite core with an air gap as shown here. The main power transformer is a low profile design, EFD size 25, using Magnetics Inc. P material which is a good choice at this frequency and temperature. The input voltage may range from 36V dc to 72V dc. Refer to application note U-170 for addi- tion design information. APPLICATION INFORMATION |
Similar Part No. - UCC1808-X |
|
Similar Description - UCC1808-X |
|
|
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 |