công cụ tìm kiếm bảng dữ liệu linh kiện điện tử
  Vietnamese  ▼
ALLDATASHEET.VN

X  

LM27402MH bảng dữ liệu(PDF) 11 Page - National Semiconductor (TI)

[Old version datasheet] Texas Instruments acquired National semiconductor.
tên linh kiện LM27402MH
Giải thích chi tiết về linh kiện  High Performance Synchronous Buck Controller with DCR Current Sensing
Download  32 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
nhà sản xuất  NSC [National Semiconductor (TI)]
Trang chủ  http://www.national.com
Logo NSC - National Semiconductor (TI)

LM27402MH bảng dữ liệu(HTML) 11 Page - National Semiconductor (TI)

Back Button LM27402MH Datasheet HTML 7Page - National Semiconductor (TI) LM27402MH Datasheet HTML 8Page - National Semiconductor (TI) LM27402MH Datasheet HTML 9Page - National Semiconductor (TI) LM27402MH Datasheet HTML 10Page - National Semiconductor (TI) LM27402MH Datasheet HTML 11Page - National Semiconductor (TI) LM27402MH Datasheet HTML 12Page - National Semiconductor (TI) LM27402MH Datasheet HTML 13Page - National Semiconductor (TI) LM27402MH Datasheet HTML 14Page - National Semiconductor (TI) LM27402MH Datasheet HTML 15Page - National Semiconductor (TI) Next Button
Zoom Inzoom in Zoom Outzoom out
 11 / 32 page
background image
Theory of Operation
GENERAL INFORMATION
The LM27402 is a single-phase synchronous voltage mode
DC/DC buck controller. The inductor DCR sense capability
and integrated low impedance gate drivers allow the
LM27402 to be used in high current, high power density ap-
plications. Multiple fault conditions are supported including
over-voltage, under-voltage, over-temperature, and over-cur-
rent. The switching frequency can be adjusted over a wide
range either by connecting a clock signal to SYNC pin or a
resistor from FADJ to GND. The LM27402 supports pre-bi-
ased outputs while maintaining synchronous mode operation.
Input voltage feed-forward is incorporated into the control
loop to mitigate the effects of input voltage variation.
UVLO
An under-voltage lockout is built into the LM27402 which al-
lows the device to only switch if the input voltage (VIN) and
the internal sub-regulated voltage (VDD) both exceed 2.9V.
A 300mV UVLO hysteresis exists on both VDD and VIN to
prevent power on and off anomalies related to input voltage
deviations.
PRECISION ENABLE (EN)
The enable pin of the LM27402 allows the output to be toggled
on and off and is a precision analog input. When the EN volt-
age exceeds 1.17V, the controller will initiate the soft-start
sequence as long as the input voltage and sub-regulated volt-
age have exceeded their UVLO thresholds of 2.9V. The EN
pin has an absolute maximum voltage rating of 6.0V and
should not exceed the voltage on VDD. There is an internal 2
µA pull-up current source connected to the EN pin. If EN is
open, the LM27402 will turn on automatically if VIN and VDD
exceed 2.9V. If the EN voltage is held below 0.8V, the
LM27402 enters a deep shutdown state where the internal
bias circuitry is off. The quiescent current is approximately 35
µA in deep shutdown. The EN pin has 100mV of hysteresis
to reject noise and allow the pin to be resistively coupled to
the input voltage or sequenced with other rails.
SOFT-START AND VOLTAGE TRACKING (SS/TRACK)
When the enable pin has exceeded 1.17V and both VIN and
VDD have exceeded their UVLO thresholds, the LM27402 will
begin charging the output linearly to the voltage level dictated
by the feedback resistor network. The soft-start time is set by
connecting a capacitor from SS/TRACK to GND. After EN
exceeds 1.17V, an internal 3 µA current source begins to lin-
early charge the soft-start capacitor. Soft-start allows the user
to limit inrush currents related to high output capacitance and
output slew rate. If a soft-start capacitor is not used, the
LM27402 defaults to a 1.28 ms digitally controlled startup
time. The SS/TRACK pin can also be used to ratiometrically
or coincidentally track an external voltage source. See the
SETTING THE SOFT-START TIME and TRACKING sections
of the design guide for more information.
PRE-BIAS STARTUP
In certain applications, the output may acquire a pre-bias volt-
age before the LM27402 is powered on or enabled. Pre-
biased conditions are managed by preventing switching until
the soft-start (SS/TRACK) voltage exceeds the feedback (FB)
voltage. Once V
SS/TRACK has exceeded VFB, the LM27402 will
begin to switch synchronously and regulate the output volt-
age.
30092645
FIGURE 1. Pre-Bias Startup
Prohibiting switching during a pre-biased startup condition
prevents the output from forcing parasitic paths to conduct
excessive current. The LM27402 will not switch if the output
is pre-biased to a voltage higher than the nominally set output
voltage.
CURRENT LIMIT
The LM27402 may enter two states when a current limit event
is detected. If a current limit condition has occurred, the high-
side FET is immediately turned off until the next switching
cycle. This is considered the first current limit state and pro-
vides an immediate response to any current limit event. Dur-
ing the first state, an internal counter will begin to record the
number of over-current events. The counter is reset if 32 con-
secutive switching cycles occur with no current limit events
detected. If five over-current events are detected within 32
switching cycles, the LM27402 then enters into a hiccup mode
state. During hiccup mode, the LM27402 will shutdown for
1.28 ms and then attempt to restart again. When transitioning
into hiccup mode, the high-side FET is turned off and the low-
side FET is turned on. As the inductor current reaches zero
subsequent to the over-current event, the low-side FET is
turned off and the switch-node becomes high impedance to
prepare for the next startup sequence. The soft-start capaci-
tor is discharged through an internal pull-down FET to reini-
tialize the startup sequence. To illustrate how the LM27402
behaves during current limit faults, an over-current scenario
is illustrated in Figure 2.
11
www.national.com


Số phần tương tự - LM27402MH

nhà sản xuấttên linh kiệnbảng dữ liệuGiải thích chi tiết về linh kiện
logo
Texas Instruments
LM27402MH/NOPB TI-LM27402MH/NOPB Datasheet
2Mb / 48P
[Old version datasheet]   LM27402 High-Performance Synchronous Buck Controller With DCR Current Sensing
LM27402MHX/NOPB TI-LM27402MHX/NOPB Datasheet
2Mb / 48P
[Old version datasheet]   LM27402 High-Performance Synchronous Buck Controller With DCR Current Sensing
More results

Mô tả tương tự - LM27402MH

nhà sản xuấttên linh kiệnbảng dữ liệuGiải thích chi tiết về linh kiện
logo
Texas Instruments
LM27402 TI-LM27402_15 Datasheet
2Mb / 48P
[Old version datasheet]   LM27402 High-Performance Synchronous Buck Controller With DCR Current Sensing
logo
Linear Technology
LTC3866 LINER-LTC3866 Datasheet
465Kb / 36P
   Current Mode Synchronous Controller for Sub Milliohm DCR Sensing
LTC3866 LINER-LTC3866_15 Datasheet
527Kb / 36P
   Current Mode Synchronous Controller for Sub Milliohm DCR Sensing
logo
Analog Devices
LTC7878 AD-LTC7878 Datasheet
1Mb / 28P
   70V Parallelable 4-Switch Buck-Boost Controller with Inductor DCR Current Sensing
Rev. 0
logo
Linear Technology
LTC3774 LINER-LTC3774_15 Datasheet
408Kb / 38P
   Dual, Multiphase Current Mode Synchronous Controller for Sub-Milliohm DCR Sensing
LTC3774 LINER-LTC3774 Datasheet
421Kb / 38P
   Dual, Multiphase Current Mode Synchronous Controller for Sub-Milliohm DCR Sensing
logo
Micro Linear Corporatio...
ML4902 MICRO-LINEAR-ML4902 Datasheet
191Kb / 12P
   High Current Synchronous Buck Controller
logo
Semtech Corporation
SC4510 SEMTECH-SC4510 Datasheet
733Kb / 16P
   High Performance Synchronous Buck Controller With Reference Tracking
logo
Micro Linear Corporatio...
ML4900 MICRO-LINEAR-ML4900 Datasheet
232Kb / 8P
   High Current Synchronous Buck Controller
ML4903 MICRO-LINEAR-ML4903 Datasheet
162Kb / 12P
   High Current Synchronous Buck 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 23 24 25 26 27 28 29 30 31 32


bảng dữ liệu tải về

Go To PDF Page


Link URL




Chính sách bảo mật
ALLDATASHEET.VN
Cho đến nay ALLDATASHEET có giúp ích cho doanh nghiệp của bạn hay không?  [ DONATE ] 

Alldatasheet là   |   Quảng cáo   |   Liên lạc với chúng tôi   |   Chính sách bảo mật   |   Trao đổi link   |   Tìm kiếm theo nhà sản xuất
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