參數(shù)資料
型號： LTC1142HV
廠商： Linear Technology Corporation
元件分類： 基準電壓源/電流源
英文描述： 500kHz and 1MHz High Efficiency 1.5A Switching Regulators; Package: SO; No of Pins: 8; Temperature Range: -40?°C to 85?°C
中文描述： 射頻放大器
文件頁數(shù)： 14/20頁
文件大?。?/td> 248K
代理商： LTC1142HV
14
LTC1142/LTC1142L/LTC1142HV
Figure 5 shows how the efficiency losses in one section of
a typical LTC1142 regulator end up being apportioned.
The gate charge loss is responsible for the majority of the
efficiency lost in the mid-current region. If Burst Mode
operation was not employed at low currents, the gate
charge loss alone would cause efficiency to drop to
unacceptable levels. With Burst Mode
operation, the DC
supply current represents the lone (and unavoidable) loss
component which continues to become a higher percent-
age as output current is reduced. As expected, the I
2
R
losses dominate at high load currents.
Other losses including C
IN
and C
OUT
ESR dissipative
losses, MOSFET switching losses, Schottky conduction
losses during dead-time and inductor core losses, gener-
ally account for less than 2% total additional loss.
and
δ
P
=
δ
N
= 0.007(63 – 25) = 0.27. The required R
DS(ON)
for each MOSFET can now be calculated:
P Ch
-
R
N-Ch R
DS(ON)
DS(ON)
=
=
=
=
12 0 25
( ) ( .
12 0 25
( ) 1 27
1 27
( .
0 12
.
0 085
.
2
( .
)
)
)
)
The P-channel requirement can be met by a Si9430DY,
while the N-channel requirement is exceeded by a
Si9410DY. Note that the most stringent requirement for
the N-channel MOSFET is with V
OUT
= 0 (i.e., short circuit).
During a continuous short circuit, the worst case
N-channel dissipation rises to:
P
N
= I
SC(AVG)2
R
DS(ON)
(1 +
δ
N
)
With the 0.05
sense resistor, I
SC(AVG)
= 2A will result,
increasing the 0.085
N-channel dissipation to 450mW at
a die temperature of 73
°
C.
C
IN
will require an RMS current rating of at least 1A at
temperature, and C
OUT
will require an ESR of 0.05
for
optimum efficiency.
Now allow V
IN
to drop to its minimum value. At lower input
voltages the operating frequency will decrease and the
P-channel will be conducting most of the time, causing its
power dissipation to increase. At V
IN(MIN)
= 7V:
f
MIN
= (1/2.92
μ
s)[1 – (5V/7V)] = 98kHz
P
V
A
V
mV
P
=
=
5 0 12
( .
2
7
435
)(
) 1 27
)
A similar calculation for the 3.3V section results in the
component values shown in Figure 14.
LTC1142HV-ADJ/LTC1142L-ADJ
Adjustable Applications
When an output voltage other than 3.3V or 5V is required,
the LTC1142 adjustable version is used with an external
resistive divider from V
OUT
to V
FB
, Pin 2 (16). The regu-
lated output voltage is determined by:
V
R
R
OUT
=
+
1.
2
1
APPLICATIU
W
U
U
Design Example
As a design example, assume V
IN
= 12V (nominal), 5V
section, I
MAX
= 2A and f = 200kHz; R
SENSE
, C
T
and L can
immediately be calculated:
R
SENSE
= 100mV/2 = 0.05
t
OFF
= (1/200kHz) [1 – (5/12)] = 2.92
μ
s
C
T5
= 2.92
μ
s/(1.3 10
4
) = 220pF
L2
MIN
= 5.1 10
5
0.05
220pF 5V = 28
μ
H
Assume that the MOSFET dissipations are to be limited to
P
N
= P
P
= 250mW.
If T
A
= 50
°
C and the thermal resistance of each MOSFET
is 50
°
C/W, then the junction temperatures will be 63
°
C
Figure 5. Efficiency Loss
OUTPUT CURRENT (A)
0.01
E
90
95
1
1142 F05
85
80
0.03
0.1
0.3
3
100
GATE CHARGE
1/2 LTC1142 I
Q
I
2
R
相關(guān)PDF資料
PDF描述
LTC1142LCG-ADJ RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS
LTC1142 OCTAL BUS TRANSCEIVER O.C. 20-SOIC 0 to 70
LTC1142CG OCTAL BUS TRANSCEIVER O.C. 20-PDIP 0 to 70
LTC1142L OCTAL BUS TRANSCEIVER O.C. 20-PDIP 0 to 70
LTC1142L-ADJ OCTAL BUS TRANSCEIVER O.C. 20-SO 0 to 70
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LTC1142HV-ADJ 制造商:LINER 制造商全稱:Linear Technology 功能描述:Dual High Efficiency Synchronous Step-Down Switching Regulators
LTC1142HVCG 功能描述:IC REG CTRLR BUCK PWM CM 28-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
LTC1142HVCG#PBF 功能描述:IC REG CTRLR BUCK PWM CM 28-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
LTC1142HVCG#TR 功能描述:IC REG CTRLR BUCK PWM CM 28-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
LTC1142HVCG#TRPBF 功能描述:IC REG CTRLR BUCK PWM CM 28-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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