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| 型号： | LTC1929CG#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 22/28页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 28-SSOP |
| 标准包装： | 47 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 360kHz |
| 占空比： | 99.5% |
| 电源电压： | 4 V ~ 36 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | 0°C ~ 85°C |
| 封装/外壳： | 28-SSOP（0.209"，5.30mm 宽） |
| 包装： | 管件 |
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LTC1929/LTC1929-PG
APPLICATIO S I FOR ATIO
Design Example
As a design example, assume V IN = 5V (nominal), V IN = 5.5V
(max), V OUT = 1.8V, I MAX = 20A, T A = 70 ° C and f = 300kHz.
The inductance value is chosen first based on a 30% ripple
The worst-case power disipated by the synchronous
MOSFET under normal operating conditions at elevated
ambient temperature and estimated 50 ° C junction tem-
perature rise is:
P SYNC =
( ) ( ) ( ) ?
current assumption. The highest value of ripple current
occurs at the maximum input voltage. Tie the FREQSET pin
to the INTV CC pin for 300kHz operation. The minimum
inductance for 30% ripple current is:
5. 5 V ? 1. 8 V
5 . 5 V
= 1 . 29 W
2
10 A 1 . 48 0 . 013
A short-circuit to ground will result in a folded back current
V OUT ? V OUT ?
? 1 ?
( )
?
? 1 ?
(
)( )( )
?
( ) ? ? = 6 . 6 A
?
+ ?
I SC =
?
?
L ≥
f ? I ? V IN ?
1 . 8 V ? 1 . 8 V ?
≥
300 kHz 30 % 10 A ? 5 . 5 V ?
≥ 1 . 35 μ H
A 1.5 μ H inductor will produce 27% ripple current. The
peak inductor current will be the maximum DC value plus
of about:
25 mV 1 200 ns 5 . 5 V
0 . 004 ? 2 ? 1 . 5 μ H ?
The worst-case power disipated by the synchronous
MOSFET under short-circuit conditions at elevated ambi-
ent temperature and estimated 50 ° C junction temperature
rise is:
( ) ( ) ( ) ?
one half the ripple current, or 11.4A. The minimum on-
time occurs at maximum V IN :
P SYNC =
5. 5 V ? 1. 8 V
5 . 5 V
6 . 6 A 1 . 48 0 . 013
2
t ON ( MIN ) =
V OUT
V IN f
=
1 . 8 V
( 5 . 5 V )( 300 kHz )
= 1 . 1 μ s
= 564 mW
which is less than half of the normal, full-load dissipation.
R SENSE = ≈ 0 . 004 ?
DF =
= = 0 . 36
TheR SENSE resistorsvaluecanbecalculatedbyusingthe
maximum current sense voltage specification with some
accomodation for tolerances:
50mV
11 . 4 A
The power dissipation on the topside MOSFET can be
easily estimated. Using a Siliconix Si4420DY for example;
R DS(ON) = 0.013 ? , C RSS = 300pF. At maximum input
voltage with T J (estimated) = 110 ° C at an elevated ambient
temperature:
Incidentally, since the load no longer dissipates power in
the shorted condition, total system power dissipation is
decreased by over 99%.
The duty factor for this application is:
V O 1 . 8 V
V IN 5 V
Using Figure 4, the RMS ripple current will be:
I INRMS = (20A)(0.23) = 4.6A RMS
An input capacitor(s) with a 4.6A RMS ripple current rating
( ) [ 1 + ( ) ( ) C ° ]
0 . 005 110 ° C ? 25
0 . 013 ? + 1 . 7 ( ) ( )( )
P MAIN =
22
1. 8 V 2
10
5 . 5 V
5 . 5 V 10 A 300 pF
( 300 kHz ) = 0 . 65 W
2
is required.
The output capacitor ripple current is calculated by using
the inductor ripple already calculated for each inductor
and multiplying by the factor obtained from Figure 3
along with the calculated duty factor. The output ripple in
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相关代理商/技术参数 |
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|---|---|
| LTC1929CG-PG | 功能描述:IC REG CTRLR BUCK PWM CM 28-SSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LTC1929CG-PG#25123 | 制造商:Linear Technology 功能描述: |
| LTC1929CG-PG#25123#TR | 制造商:Linear Technology 功能描述: |
| LTC1929CG-PG#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 28-SSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LTC1929CG-PG#TR | 功能描述:IC REG CTRLR BUCK PWM CM 28-SSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
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