- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄377776 > LTC3770EG (LINEAR TECHNOLOGY CORP) Synchronous Controller with Margining, Tracking and PLL PDF資料下載
參數(shù)資料
| 型號： | LTC3770EG |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Synchronous Controller with Margining, Tracking and PLL |
| 中文描述： | 4 A SWITCHING CONTROLLER, PDSO28 |
| 封裝： | 5.30 MM, PLASTIC, SSOP-28 |
| 文件頁數(shù)： | 20/24頁 |
| 文件大?。?/td> | 302K |
| 代理商： | LTC3770EG |
20
LTC3770
3770f
If you make a change and the input current decreases, then
the efficiency has increased. If there is no change in input
current, then there is no change in efficiency.
Checking Transient Response
The regulator loop response can be checked by looking at
the load transient response. Switching regulators take
several cycles to respond to a step in load current. When
a load step occurs, V
OUT
immediately shifts by an amount
equal to
I
LOAD
(ESR), where ESR is the effective series
resistance of C
OUT
.
I
LOAD
also begins to charge or
discharge C
OUT
generating a feedback error signal used by
the regulator to return V
OUT
to its steady-state value.
During this recovery time, V
OUT
can be monitored for
overshoot or ringing that would indicate a stability prob-
lem. The I
TH
pin external components shown in Figure 12
will provide adequate compensation for most applica-
tions. For a detailed explanation of switching control loop
theory see Application Note 76.
Design Example
As a design example, take a supply with the following
specifications: V
IN
= 5V to 28V (15V nominal), V
OUT
= 2.5V
±
5%, I
OUT(MAX)
= 10A, f = 450kHz. First, calculate the
timing resistor with V
ON
= V
OUT
:
V
V
kHz
)(
)(
and choose the inductor for about 40% ripple current at
the maximum V
IN
:
R
pF
k
ON
=
)
=
2 5
450
3 2 5
10
74
.
.
L
V
.
kHz
A
V
V
H
=
(
)(
)
=
μ
2 5
.
450
0 4 10
1
2 5
28
1 3
.
.
Selecting a standard value of 1.8
μ
H results in a maximum
ripple current of:
=
(
)
μ
(
)
=
I
V
1 8
.
kHz
H
V
V
A
L
2 5
.
450
1
2 5
28
2 8
.
–
.
Next, choose the synchronous MOSFET switch. Choosing
a Si4874 (R
DS(ON)
= 0.0083
(NOM) 0.010
(MAX),
θ
JA
= 40
°
C/W) yields a nominal sense voltage of:
V
SNS(NOM)
= (10A)(1.3)(0.0083
) = 108mV
Tying V
RNG
to 1.1V will set the current sense voltage range
for a nominal value of 110mV with current limit occurring
at 146mV. To check if the current limit is acceptable,
assume a junction temperature of about 80
°
C above a
70
°
C ambient with
ρ
150
°
C
= 1.5:
mV
LIMIT
≥
(
and double check the assumed T
J
in the MOSFET:
V
V
V
28
T
J
= 70
°
C + (1.65W)(40
°
C/W) = 136
°
C
Because the top MOSFET is on for such a short time, an
Si4884 R
DS(ON)(MAX)
= 0.0165
, C
RSS
= 100pF,
θ
JA
=
40
°
C/W will be sufficient. Checking its power dissipation
at current limit with
ρ
100
°
C
= 1.4:
V
V
V
A
W
W
=
+
=
0 25
0 37
.
.
I
A
A
)
+
(
)
=
146
1 5 0 010
.
1
22 8
11
.
.
P
A
W
BOT
=
(
) (
)
=
28
–2 5
11
15 0 010
.
165
.
.
P
A
pF
.
kHz
W
TOP
=
(
) (
)
+
(
) (
)(
)(
)
2 5
28
1 7 28
.
11
1 4 0 0165
.
11
100
250
0 62
.
.
T
J
= 70
°
C + (0.62W)(40
°
C/W) = 95
°
C
The junction temperature will be significantly less at
nominal current, but this analysis shows that careful
attention to heat sinking on the board will be necessary in
this circuit.
C
IN
is chosen for an RMS current rating of about 3A at
85
°
C. The output capacitors are chosen for a low ESR of
0.013
to minimize output voltage changes due to induc-
tor ripple current and load steps. The ripple voltage will be
only:
V
OUT(RIPPLE)
=
I
L(MAX)
(ESR)
= (2.8A) (0.013
) = 36mV
However, a 0A to 10A load step will cause an output
change of up to:
V
OUT(STEP)
=
I
LOAD
(ESR) = (10A) (0.013
) = 130mV
An optional 22
μ
F ceramic output capacitor is included to
minimize the effect of ESL in the output ripple. The
complete circuit is shown in Figure 12.
APPLICATIU
W
U
U
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LTC3770EUH | Synchronous Controller with Margining, Tracking and PLL |
| LTC3776 | 16-Bit Buffer/Driver With 3-State Outputs 48-TVSOP -40 to 85 |
| LTC3776EUF | Dual 2-Phase, No RSENSE Synchronous Controller for DDR/QDR Memory Termination |
| LTC3776EGN | Dual 2-Phase, No RSENSE Synchronous Controller for DDR/QDR Memory Termination |
| LTC3780 | DIODE SCHOTTKY DUAL ISOLATED 25V 150mW 0.33V-vf 200mA-IFM 2mA-IF 0.5uA-IR SOT-563 3K/REEL |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LTC3770EG#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(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 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:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
| LTC3770EG#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(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 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:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
| LTC3770EUH#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 32-QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 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:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
| LTC3770EUH#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 32-QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 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:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
| LTC3772BEDDB#TRMPBF | 功能描述:IC REG CTRLR BUCK PWM CM 8-DFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 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:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。