数据搜索系统,热门电子元器件搜索
  Chinese  ▼
ALLDATASHEETCN.COM

X  

FAN5069 数据表(PDF) 11 Page - Fairchild Semiconductor

部件名 FAN5069
功能描述  PWM and LDO Controller Combo
Download  22 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
制造商  FAIRCHILD [Fairchild Semiconductor]
网页  http://www.fairchildsemi.com
标志 FAIRCHILD - Fairchild Semiconductor

FAN5069 数据表(HTML) 11 Page - Fairchild Semiconductor

Back Button FAN5069_08 Datasheet HTML 7Page - Fairchild Semiconductor FAN5069_08 Datasheet HTML 8Page - Fairchild Semiconductor FAN5069_08 Datasheet HTML 9Page - Fairchild Semiconductor FAN5069_08 Datasheet HTML 10Page - Fairchild Semiconductor FAN5069_08 Datasheet HTML 11Page - Fairchild Semiconductor FAN5069_08 Datasheet HTML 12Page - Fairchild Semiconductor FAN5069_08 Datasheet HTML 13Page - Fairchild Semiconductor FAN5069_08 Datasheet HTML 14Page - Fairchild Semiconductor FAN5069_08 Datasheet HTML 15Page - Fairchild Semiconductor Next Button
Zoom Inzoom in Zoom Outzoom out
 11 / 22 page
background image
© 2005 Fairchild Semiconductor Corporation
www.fairchildsemi.com
FAN5069 Rev. 1.1.5
11
PWM Operation
Refer to Figure 20 for the PWM control mechanism. The
FAN5069 uses the summing mode method of control to
generate the PWM pulses. The amplified output of the
current-sense amplifier is summed with an internally
generated ramp and the combined signal is amplified
and compared with the output of the error amplifier to get
the pulse width to drive the high-side MOSFET. The
sensed current from the previous cycle is used to modu-
late the output of the summing block. The output of the
summing block is also compared against the voltage
threshold set by the RLIM resistor to limit the inductor cur-
rent on a cycle-by-cycle basis. The controller facilitates
external compensation for enhanced flexibility.
Initialization
When the PWM is disabled, the SW node is connected
to GND through an internal 500
Ω MOSFET to slowly dis-
charge the output. As long as the PWM controller is
enabled, this internal MOSFET remains OFF.
Soft-Start (PWM and LDO)
When VCC exceeds the UVLO threshold and EN is high,
the circuit releases SS and enables the PWM regulator.
The capacitor connected to the SS pin and GND is
charged by a 10µA internal current source, causing the
voltage on the capacitor to rise. When this voltage
exceeds 1.2V, all protection circuits are enabled. When
this voltage exceeds 2.2V, the LDO output is enabled.
The input to the error amplifier at the non-inverting pin is
clamped by the voltage on the SS pin until it crosses the
reference voltage.
The time it takes the PWM output to reach regulation
(TRise) is calculated using the following equation:
(CSS is in μf)
(EQ. 2)
Oscillator Clock Frequency (PWM)
The clock frequency on the oscillator is set using an
external resistor, connected between R(T) pin and
ground. The frequency follows the graph, as shown in
Figure 18. The minimum clock frequency is 200KHz,
which is when R(T) pin is left open. Select the value of
R(T) as shown in the equation below. This equation is
valid for all FOSC > 200kHz.
(EQ. 3)
where FOSC is in Hz.
For example, for FOSC = 300kHz, R(T) = 50KΩ.
RRAMP Selection and Feed-Forward Operation
The FAN5069 provides for input voltage feed-forward
compensation through RRAMP. The value of RRAMP effec-
tively changes the slope of the internal ramp, minimizing
the variation of the PWM modulator gain when input volt-
age varies. The RRAMP also has an effect on the current
limit, as can be seen in the RLIM equation (EQ. 5). The
RRAMP value can be approximated using the following
equation:
K
Ω
(EQ. 4)
where FOSC is in Hz. For example, for FOSC = 300kHz
and VIN = 12V, RRAMP
540K
Ω.
Gate Drive Section
The adaptive gate control logic translates the internal
PWM control signal into the MOSFET gate drive signals
and provides necessary amplification, level shifting, and
shoot-through protection. It also has functions that help
optimize the IC performance over a wide range of oper-
ating conditions. Since the MOSFET switching time can
vary dramatically from device to device and with the
input voltage, the gate control logic provides adaptive
dead time by monitoring the gate-to-source voltages of
both upper and lower MOSFETs. The lower MOSFET
drive is not turned on until the gate-to-source voltage of
the upper MOSFET has decreased to less than approxi-
mately 1V. Similarly, the upper MOSFET is not turned on
until the gate-to-source voltage of the lower MOSFET
has decreased to less than approximately 1V. This
allows a wide variety of upper and lower MOSFETs to be
used without a concern for simultaneous conduction, or
shoot-through.
A low impedance path between the driver pin and the
MOSFET gate is recommended for the adaptive dead-
time circuit to work properly. Any delay along this path
reduces the delay generated by the adaptive dead-time
circuit, thereby increasing the chances for shoot-through.
Protection
In the FAN5069, the converter is protected against
extreme overload, short-circuit, over-voltage, and under-
voltage conditions. All of these conditions generate an
internal “fault latch” which shuts down the converter. For
all fault conditions both the high-side and the low-side
drives are off except in the case of OVP where the low-
side MOSFET is turned on until the voltage on the FB pin
goes below 0.4V. The fault latch can be reset either by
toggling the EN pin or recycling VCC to the chip.
Over Current Limit (PWM)
The PWM converter is protected against overloading
through a cycle-by-cycle current limit set by selecting
RILIM resistor. An internal 10µA current source sets the
threshold voltage for the output of the summing amplifier.
When the summing amplifier output exceeds this thresh-
old level, the current limit comparator trips and the PWM
starts skipping pulses. If the current limit tripping occurs
for 16 continuous clock cycles, a fault latch is set and the
controller shuts down the converter. This shutdown fea-
T
RISE
810
2
×
C
SS
×
=
RT
()
510
9
×
F
OSC
200
103
×
()
---------------------------------------------------
Ω
=
R
RAMP
V
IN
1.8
6.3
10
8
Fosc
---------------------------------------------
=


类似零件编号 - FAN5069_08

制造商部件名数据表功能描述
logo
Fairchild Semiconductor
FAN5069 FAIRCHILD-FAN5069_06 Datasheet
621Kb / 22P
   PWM and LDO Controller Combo
More results

类似说明 - FAN5069_08

制造商部件名数据表功能描述
logo
Fairchild Semiconductor
FAN5069 FAIRCHILD-FAN5069 Datasheet
379Kb / 20P
   PWM and LDO Controller Combo
FAN5069 FAIRCHILD-FAN5069_06 Datasheet
621Kb / 22P
   PWM and LDO Controller Combo
logo
International Rectifier
IRU3048 IRF-IRU3048 Datasheet
154Kb / 18P
   DUAL SYNCHRONOUS PWM CONTROLLER CIRCUITRY AND LDO CONTROLLER
logo
Advanced Power Electron...
APU3048 A-POWER-APU3048 Datasheet
189Kb / 15P
   DUAL SYNCHRONOUS PWM CONTROLLER CIRCUITRY AND LDO CONTROLLER
logo
Microsemi Corporation
NX2139A MICROSEMI-NX2139A Datasheet
857Kb / 21P
   SINGLE CHANNEL MOBILE PWM AND LDO CONTROLLER
logo
Fairchild Semiconductor
FAN5099 FAIRCHILD-FAN5099 Datasheet
1,018Kb / 24P
   Wide Frequency Synchronous Buck PWM AND LDO Controller
logo
Micro Linear Corporatio...
ML4819 MICRO-LINEAR-ML4819 Datasheet
290Kb / 15P
   Power Factor and PWM Controller Combo
logo
International Rectifier
IRU3046 IRF-IRU3046 Datasheet
163Kb / 20P
   DUAL SYNCHRONOUS PWM CONTROLLER WITH CURRENT SHARING CIRCUITRY AND LDO CONTROLLER
IRU3047 IRF-IRU3047 Datasheet
141Kb / 19P
   DUAL SYNCHRONOUS PWM CONTROLLER WITH CURRENT SHARING CIRCUITRY AND LDO CONTROLLER
logo
Microsemi Corporation
LX2750 MICROSEMI-LX2750 Datasheet
394Kb / 11P
   SINGLE INPUT SUPPLY PWM CONTROLLER WITH LDO CONTROLLER
More results


Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22


数据表 下载

Go To PDF Page


链接网址




隐私政策
ALLDATASHEETCN.COM
ALLDATASHEET是否为您带来帮助?  [ DONATE ] 

关于 Alldatasheet   |   广告服务   |   联系我们   |   隐私政策   |   链接交换   |   制造商名单
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
Indian : Alldatasheet.in  |   Mexican : Alldatasheet.com.mx  |   British : Alldatasheet.co.uk  |   New Zealand : Alldatasheet.co.nz
Family Site : ic2ic.com  |   icmetro.com