Electronic Components Datasheet Search
  English  ▼

Delete All


Preview PDF Download HTML

STR-F6600 Datasheet(PDF) 6 Page - Allegro MicroSystems

Part No. STR-F6600
Download  16 Pages
Scroll/Zoom Zoom In 100% Zoom Out
Maker  ALLEGRO [Allegro MicroSystems]
Homepage  http://www.allegromicro.com
Logo ALLEGRO - Allegro MicroSystems

STR-F6600 Datasheet(HTML) 6 Page - Allegro MicroSystems

Back Button STR-F6600 Datasheet HTML 2Page - Allegro MicroSystems STR-F6600 Datasheet HTML 3Page - Allegro MicroSystems STR-F6600 Datasheet HTML 4Page - Allegro MicroSystems STR-F6600 Datasheet HTML 5Page - Allegro MicroSystems STR-F6600 Datasheet HTML 6Page - Allegro MicroSystems STR-F6600 Datasheet HTML 7Page - Allegro MicroSystems STR-F6600 Datasheet HTML 8Page - Allegro MicroSystems STR-F6600 Datasheet HTML 9Page - Allegro MicroSystems STR-F6600 Datasheet HTML 10Page - Allegro MicroSystems Next Button
Zoom Inzoom in Zoom Outzoom out
 6 / 16 page
background image
Series STR-F6600
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
Functional Description and Operation (cont’d)
Figure 4 – Output Current I
OUT – Terminal Voltage VIN
Figure 5 – Soft-Start Operation
The drive winding voltage is set such that in normal
operation the C2 voltage is above the specified maximum
shutdown voltage (11 V) and below the specified mini-
mum over-voltage threshold (20.5 V).
In applications where there is a significant variation in
load current, the V
IN terminal voltage may vary, as shown
in figure 4. This is due to peak charging of C2. In this
case, adding a resistor in the range of a few ohms to tens of
ohms in series with the rectifier diode D2 will bring the
voltage variation within limits.
Soft Start, Quasi Resonant and Voltage Regulation
Refer to the Functional Block Diagram and the Typical
Application Diagram (figure 6). The internal oscillator
uses the charge/discharge of an internal 4700 pF capacitor
SS) to generate the MOSFET drive signals.
The regulator has two modes of operation:
1. fixed 50
µs off time (soft start) and
2. demagnetization sensing quasi-resonant mode —
normal operation.
In both cases, voltage regulation is achieved by taking
the composite optocoupled voltage error and superimposed
drain current ramp (current-mode control) and comparing
this to an internal 0.73 V reference. The FBK/OCP
comparator output pre-terminates the oscillator, which
turns off the MOSFET drive signal.
The MOSFET is turned on again when either c
discharges or a quasi-resonance signal is detected on pin 1.
Fixed 50
µs Off-Time: Soft-Start Mode
This is the mode of operation in the absence of a quasi-
resonance signal on pin 1 (see figure 5), and occurs at
startup and in overload. It also can be commanded exter-
nally to provide low-power standby operation.
In the absence of a feedback signal (such as at startup,
or a short circuit) the drain current ramp, sensed across R5
and noise filtered by R4/C5 appears on pin 1. When the
ramp voltage on C5 exceeds the 0.73 V reference signal,
the FBK/OCP comparator changes state, shutting down the
oscillator and turning off the MOSFET. Thus the voltage
on c
SS is held high (6.5 V) by the comparator. When the
comparator changes state, c
SS discharges via rSS; the
voltage on c
SS ramps down until it reaches 3.7 V. The
oscillator turns on the MOSFET. This ramp-down time is
internally trimmed to 50
µs. The comparator changes state
again and the cycle repeats. Thus in the absence of
feedback, the current-sense resistor R5 accurately controls
the MOSFET maximum current.

Html Pages

1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16 

Datasheet Download

Go To PDF Page

Link URL

Privacy Policy
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