Electronic Components Datasheet Search
  English  ▼

Delete All
ON OFF
ALLDATASHEET.COM

X  

Preview PDF Download HTML

UCC28251 Datasheet(PDF) 20 Page - Texas Instruments

Part No. UCC28251
Description  UCC28251 Advanced PWM Controller With Prebias Operation
Download  55 Pages
Scroll/Zoom Zoom In 100% Zoom Out
Maker  TI [Texas Instruments]
Homepage  http://www.ti.com
Logo 

UCC28251 Datasheet(HTML) 20 Page - Texas Instruments

Zoom Inzoom in Zoom Outzoom out
 20 / 55 page
background image
CS
CHARGE
CS
SW
CHARGE
PK
1
R
V
2
ln
C
f
V
V
=
æ
ö
´
´
´
ç
÷
-
è
ø
+
æ
ö
<
´
ç
÷
W
è
ø
D(SP)
CS
T
70ns
4 V / 2
C
40
4 V
0
240
RPS - PS Resistor - kW
0
100
150
400
120
300
PS DEAD TIME
vs
PS RESISTOR
250
200
50
100
80
60
40
20
140 160 180 200 220
350
UCC28251
SLUSBD8E – FEBRUARY 2013 – REVISED DECEMBER 2014
www.ti.com
Feature Description (continued)
Figure 28. Dead Time TD(ps) vs. External Resistor RPS at PS Pin
8.3.7 RAMP/CS (PWM Ramp Input or Current Sense Input) (16/3)
The UCC28251 can be controlled using either voltage mode or current mode. RAMP/CS is a multi-function pin
used either to generate the ramp signal for voltage mode control or to sense current for current mode control.The
following sections describe the RAMP/CS functionality for voltage mode and current mode control.
8.3.7.1 RAMP: Voltage Mode Control With Feed-Forward Operation
For voltage mode control, a resistor RCS and a capacitor CCS must be connected to the RAMP/CS pin as shown
in Figure 29. The internal pull-down switch has approximately 40-
Ω on-resistance. The RAMP/CS pin is clamped
internally to not exceed 4 V for internal device protection. The CCS value must be small enough to discharge the
RAMP/CS pin from its peak voltage to ground within the pulse width of the BLANK signal (TD(sp) + 70 ns). The
following formula derives a CCS value.
(4)
A CCS value less than 650 pF works for most applications. In order to minimize the impacts of parasitic
capacitance caused by the PCB layout and routing, a minimum of 100 pF is recommended for CCS. Once CCS is
determined, RCS can be calculated according to the desired ramp peak amplitude.
(5)
In this equation, the VCHARGE is the voltage used to generate the ramp, VPK is the desired ramp amplitude and
the fSW is the switching frequency.
20
Submit Documentation Feedback
Copyright © 2013–2014, Texas Instruments Incorporated
Product Folder Links: UCC28251


Html Pages

1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30  31  32  33  34  35  36  37  38  39  40  41  42  43  44  45  46  47  48  49  50  51  52  53  54  55 


Datasheet Download




Link URL




Privacy Policy
ALLDATASHEET.COM
Does ALLDATASHEET help your business so far?  [ DONATE ]  

About Alldatasheet   |   Advertisement   |   Datasheet Upload   |   Contact us   |   Privacy Policy   |   Alldatasheet API   |   Link Exchange   |   Manufacturer List
All Rights Reserved© Alldatasheet.com


Mirror Sites
English : Alldatasheet.com  |   English : Alldatasheet.net  |   Chinese : Alldatasheetcn.com  |   German : Alldatasheetde.com  |   Japanese : Alldatasheet.jp
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