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參數(shù)資料
| 型號： | LT1738IG |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Slew Rate Controlled Ultralow Noise DC/DC Controller |
| 中文描述： | 0.3 A SWITCHING CONTROLLER, 250 kHz SWITCHING FREQ-MAX, PDSO20 |
| 封裝： | 5.30 MM, PLASTIC, SSOP-20 |
| 文件頁數(shù)： | 11/20頁 |
| 文件大?。?/td> | 248K |
| 代理商： | LT1738IG |
11
LT1738
1738fa
APPLICATIU
Reducing EMI from switching power supplies has tradi-
tionally invoked fear in designers. Many switchers are
designed solely on efficiency and as such produce wave-
forms filled with high frequency harmonics that then
propagate through the rest of the system.
The LT1738 provides control over two of the more impor-
tant variables for controlling EMI with switching inductive
loads: switch voltage slew rate and switch current slew
rate. The use of this part will reduce noise and EMI over
conventional switch mode controllers. Because these
variables are under control, a supply built with this part will
exhibit far less tendency to create EMI and less chance of
encountering problems during production.
It is beyond the scope of this data sheet to get into EMI
fundamentals. Application Note 70 contains much infor-
mation concerning noise in switching regulators and
should be consulted.
W
U
U
OPERATIOU
Oscillator Frequency
The oscillator determines the switching frequency and
therefore the fundamental positioning of all harmonics.
The use of good quality external components is important
to ensure oscillator frequency stability. The oscillator is of
a sawtooth design. A current defined by external resistor
R
T
is used to charge and discharge the capacitor C
T
. The
discharge rate is approximately ten times the charge rate.
By allowing the user to have control over both compo-
nents, trimming of oscillator frequency can be more easily
achieved.
The external capacitance C
T
is chosen by:
2180
C nF
f kHz R k
(
)
(
)
(
)
=
where f is the desired oscillator frequency in kHz. For R
T
equal to 16.9k, this simplifies to:
C nF
f kHz
(
(
)
)
=
129
e.g., C
T
= 1.29nF for f = 100kHz
Nominally R
T
should be 16.9k. Since it sets up current, its
temperature coefficient should be selected to compliment
the capacitor. Ideally, both should have low temperature
coefficients.
Table 1. Safety and Protection Features
FEATURE
Maximum Current Fault
FUNCTION
Turn Off FET at Maximum
Switch Current (V
SENSE
= 0.1)
Turn Off FET and Reset V
C
for Short-Circuit (V
SENSE
= 0.22)
Turn Off Driver If FB > V
REG
+ 0.22V
(Output Overvoltage)
Set Max Gate Voltage to Prevent
FET Gate Breakdown
Disable Gate Drive When V
IN
Is Too Low. Set Via GCL Pin
Turn Off Driver If Chip
Temperature Is Too Hot
Disable Part When V
IN
2.55V
Limit Gate Drive Current
Limit Current from V5
Disable Part When SHDN <1.3V
EFFECT on GATE DRIVER
Immediately Goes Low
SLEW CONTROL EFFECT on V
C
, SS
Overridden
None
Short-Circuit Fault
Immediately Goes Low
Overridden
Discharge V
C
, SS
to GND
None
Overvoltage Fault
Immediately Goes Low
Overridden
GCL Clamp
Limits Max Voltage
None
None
Gate Drive
Undervoltage Lockout
Thermal Shutdown
Immediately Goes Low
Overridden
None
Immediately Goes Low
Overridden
None
V
IN
Undervoltage Lockout
Gate Drive Source and Sink Current Limit
V5 Source/Sink Current Limit
Shutdown
Immediately Goes Low
Limit Drive Current
None
Overridden
None
None
None
None
None
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| LT1738IG#PBF | 功能描述:IC REG CTRLR PWM CM 20-SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標準包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
| LT1738IG#PBF | 制造商:Linear Technology 功能描述:ICSMPS CONTROLLERCURRENT-MODESSOP20P 制造商:Linear Technology 功能描述:IC,SMPS CONTROLLER,CURRENT-MODE,SSOP,20P |
| LT1738IG#TR | 功能描述:IC REG CTRLR PWM CM 20-SSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標準包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
| LT1738IG#TRPBF | 功能描述:IC REG CTRLR PWM CM 20-SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標準包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
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