参数资料
| 型号： | SC4525ASETRT |
| 厂商： | Semtech |
| 文件页数： | 14/19页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK 3A 8SOIC |
| 标准包装： | 1 |
| 类型： | 降压（降压） |
| 输出数： | 1 |
| 输入电压： | 8 V ~ 28 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 300kHz ~ 1.3MHz |
| 电流 - 输出： | 3A |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm Width）裸露焊盘 |
| 包装： | 标准包装 |
| 供应商设备封装： | 8-SOIC-EP |
| 产品目录页面： | 1358 (CN2011-ZH PDF) |
| 其它名称： | SC4525ASEDKR |
2 π ? 16 ? 10 ? 22 . 1 ? 10 3
C 5 =
1
3
= 0 . 45 nF
SC4525A
C 8 =
1
2 π ? 600 ? 10 3 ? 22 . 1 ? 10 3
= 12 pF
V o G PWM ( 1 + s R ESR C O )
(3) Place the compensator zero, F Z , 2 between 0% and
V c ( 1 + s / ω p ) ( 1 + s / ω n Q + s / ω 2 )
G PWM ≈
ω p ≈
ω Z =
F Z . R 1
(5) Then, the parameters of the compensation network R
G CA ? R S
1 conduction loss P C , the switching loss P SW , and bootstrap
circuit P loss P BST, P can + P be SW estimated P as follows:
TOTAL =
+ P BST + Q
ApplicationsInformation(Cont.)
=
20% of the crossover frequency, F C .
(4) Use the compensator pole, F P , to cancel the ESR zero,
, ,
R C O
can be calculated by
Thermal Considerations
For the power transistor inside the SC4525A, the
,
ESR C O C
10 20
P SW =
? t S ? V IN ? I O ? F SW
P BST = D ? V BST ?
R 7 =
C 5 =
C 8 =
A C
g m
1
2 π F Z 1 R 7
1
2 π F P 1 R 7
P C = D ? V CESAT ? I O
1
2
I O
40
P Q = V IN ? 2 mA
( 0)
where g m =0.28mA/V is the EA gain of the SC4525A.
Example : Determine the voltage compensator for an
V ( 1 ? D ) ? D ? I O D
where P BST = is the BST V supply voltage and t S is the equivalent
switching time of the NPN transistor (see Table 4).
Input Voltage
800kHz, 2V to 3.3V/3A converter with 47uF ceramic
output capacitor.
P 1 ~ 1 . 3 ? I 2O ? R DC IND = 1
Table ( 4. . Typical ) switching time
Load Current
1A 2A
3A
Choose a loop gain crossover frequency of 80kHz, and
place voltage compensator zero 1 and pole ? at F Z = 6kHz
?
V FB
(20% of F = C ), ? ? ? 20 1 ? log P ? ? 1 =600kHz. 2 π From Equation (9), the
1 28V 25.3ns 28ns 31ns
and F G R V FB ? ? ?
A C
?
required compensator F C gain V at ? ? F C is
A C = ? 20 ? log ? ? ? CA ? S F C C O V O ?
P TOTAL = P C + P SW + P BST In P addition, the quiescent current loss is
A C = ? A 20 C ? = log ? ? 20 ? log ? ? 3 ?
? 1 ? 1 1 1 . 0 ? 1 1 . 0 ?
? 28 ? 4 . 1 ? 10 28 2 ? π 4 ? . 1 ? ? 10 3 ? 3 ? 47 2 10 ? ? 6 80 3 . ? 3 10 3 ? 47 ? 10 ? 6
? π
?
3 . 3 ?
P C = D ? V CESAT ? I O
10
The total power loss of the SC4525A is therefore
R 7 =
= 31 . 19 8 k
0 . 28 ? 10 ? 3 10 20
P SW =
? t S ? V IN ? I O ? F SW
R 7 = 1 = 31 . 8 k 2
P TOTAL = P C + P SW + P BST + P Q
C 5 = 0 . 28 ? 10 ? 3 = 0 . 31 nF
C 5 =
= P 0 BST . 31 = nF ? V BST ?
1 I O
1 D
2 π ? 600 2 10 3 ? 16 . ? 4 10 3 ? 31 . 4 ? 10
? π ? 31 ? 10
40
The temperature rise ? of the SC4525A P is Q the V product of the
= IN ? 2 mA
P C = D ? V CESAT I O
total power dissipation (Equation ( 2)) and q JA (36 o C/W),
C 8 = G
= 8 . 5 pF
1
2 π ? 600 ? 10 2 ? 31 . 4 ? 10 3 P D = ( 1 ? D ) ? V D ? I O
1
which is the thermal impedance from junction to ambient
P SW =
? t S ? V IN ? I O ?
for the SOIC-8 2 EDP package. F SW
V o PWM ( 1 + s R ESR C O ) 3
=
( 1 + s / ω p ) ( 1 + s / ω n Q + s / ω n )
V c
I
G PWM ≈ ( 1 1 + , s R ESR C O ω ) Z P = IND 1 = ( 1 , . 1 ~ 1 . 3 ) ? I O ? R DC It is not BST recommended O to operate the SC4525A above
G PWM ≈ V o R , ω p P = D ? V BST ?
V c CA ( S 1 + s / ω p ) ( 1 + O s / ω n Q + s / ω ESR n 2 )
upon request for detailed calculation of the compensator
frequency = may ? D need D to I O be reduced to meet the thermal
10
) ? V ?
P D
( 1
R 7 =
parameters.
1 requirement.
R
1
G CA ? R S
G PWM ≈ , ω p ≈ , ω Z = ,
P IND = ( 1 . 1 ~ 1 . 3 ) ? I 2O ? R DC
C 5 = R C O R ESR C O
12V 12.5ns 15.3ns 18ns
24V 22ns 25ns 28ns
? ?
? G CA R S 2 π C O O
? ? ? = 19 dB ? ? = 19 dB
80 10 ?
P Q = V IN ? 2mA ( )
19
Then the compensator parameters are
20
1
2 π ? 16 ? 10 3 ? 31 . 4 ? 10 3 ( 2)
C 8 = 3 = 8 . 5 pF 3
2
Select R 7 =3 .4k, C 5 =0.33nF, and C 8 = 0pF for the design.
2
? G = R 2 O 40 R R C
A C
Compensator parameters C for various typical applications 25 o C junction temperature. In the applications with high
are listed in Table 5. A MathCAD program is also available input voltage and high output current, the switching
20
g m
2 π F Z 1 R 7
2 R π F P 1 = R 7 10
g m
C 8 =
1 A C
7
20
C 5 =
1
4
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| SC4525C | 制造商:SEMTECH 制造商全称:Semtech Corporation 功能描述:28V 3A Step-Down Switching Regulator Thermal Shutdown |
| SC4525CSETRT | 功能描述:IC REG BUCK ADJ 3A 8SOIC RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:250 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V 输入电压:2.05 V ~ 6 V PWM 型:电压模式 频率 - 开关:2MHz 电流 - 输出:500mA 同步整流器:是 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:6-UFDFN 包装:带卷 (TR) 供应商设备封装:6-SON（1.45x1） 产品目录页面:1032 (CN2011-ZH PDF) 其它名称:296-25628-2 |
| SC4525D | 制造商:SEMTECH 制造商全称:Semtech Corporation 功能描述:18V, 3A, 350kHz Step-Down Switching Regulator |
| SC4525DEVB | 制造商:SEMTECH 制造商全称:Semtech Corporation 功能描述:18V, 3A, 350kHz Step-Down Switching Regulator |
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