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参数资料
| 型号： | MAX17024ETD+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 17/25页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR DIVIDER PWM 14TDFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| 系列： | Quick-PWM™ |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 600kHz |
| 电源电压： | 2 V ~ 26 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 是 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | 0°C ~ 85°C |
| 封装/外壳： | 14-WFDFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
Single Quick-PWM Step-Down
Controller with Dynamic REFIN
?
Inductor operating point: This choice provides
trade-offs between size vs. efficiency and transient
The amount of overshoot due to stored inductor energy
when the load is removed can be calculated as:
response vs. output noise. Low inductor values pro-
vide better transient response and smaller physical
size, but also result in lower efficiency and higher
output noise due to increased ripple current. The
V SOAR
≈
( ? I LOAD(MAX ) ) 2 L
2 C OUT V OUT
minimum practical inductor value is one that causes
the circuit to operate at the edge of critical conduc-
tion (where the inductor current just touches zero
with every cycle at maximum load). Inductor values
lower than this grant no further size-reduction bene-
fit. The optimum operating point is usually found
Setting the Valley Current Limit
The minimum current-limit threshold must be high
enough to support the maximum load current when the
current limit is at the minimum tolerance value. The val-
ley of the inductor current occurs at I LOAD(MAX) minus
half the inductor ripple current ( ? I L ), therefore:
between 20% and 50% ripple current.
Inductor Selection
The switching frequency and operating point (% ripple
I LIMIT ( LOW ) > I LOAD ( MAX ) ?
? I L
2
L = ? ? ? ?
I PEAK LOAD ( MAX ) +
? I L
( R ESR + R PCB ) ≤ ? I
L ( ? I LOAD(MAX) ) ? ? OUT SW ? + t OFF ( MIN ) ?
?
?
? ? ( V IN OUT ) T SW ?
V SAG =
? ? ?
? ?
2 C OUT V OUT ? ? ? ? t OFF ( MIN ) ?
? ?
R ESR ≤ ?
? V RIPPLE
? ? ( V IN OUT ) V OUT ? ?
current or LIR) determine the inductor value as follows:
? V IN ? V OUT ? ? V OUT ?
? f SW I LOAD ( MAX ) LIR ? ? V IN ?
Find a low-loss inductor having the lowest possible DC
resistance that fits in the allotted dimensions. Ferrite
cores are often the best choice, although powdered
iron is inexpensive and can work well at 200kHz. The
core must be large enough not to saturate at the peak
inductor current (I PEAK ):
= I
2
Transient Response
The inductor ripple current impacts transient-response
performance, especially at low V IN - V OUT differentials.
Low inductor values allow the inductor current to slew
faster, replenishing charge removed from the output fil-
ter capacitors by a sudden load step. The amount of
output sag is also a function of the maximum duty factor,
which can be calculated from the on-time and minimum
off-time. The worst-case output sag voltage can be
determined by:
2 ? ? V T ? ?
? V IN ?
? V ?
V IN ?
where t OFF(MIN) is the minimum off-time (see the Electrical
Characteristics table).
where I LIMIT(LOW) equals the minimum current-sense
threshold voltage (see the Electrical Characteristics
table) divided by the low-side MOSFET sense resis-
tance R CS .
Output Capacitor Selection
The output filter capacitor must have low-enough effec-
tive series resistance (ESR) to meet output ripple and
load-transient requirements. Additionally, the ESR
impacts stability requirements. Capacitors with a high
ESR value (polymers/tantalums) do not need additional
external compensation components.
In core and chipset converters and other applications
where the output is subject to large-load transients, the
output capacitor’s size typically depends on how much
ESR is needed to prevent the output from dipping too
low under a load transient. Ignoring the sag due to
finite capacitance:
V STEP
LOAD ( MAX )
In low-voltage applications, the output capacitor’s size
often depends on how much ESR is needed to maintain
an acceptable level of output ripple voltage. The output
ripple voltage of a step-down controller equals the total
inductor ripple current multiplied by the output capaci-
tor’s ESR. The maximum ESR to meet ripple require-
ments is:
V IN f SW L
? V
where f SW is the switching frequency.
______________________________________________________________________________________
17
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| MAX17028GTJ+T | 功能描述:电压模式 PWM 控制器 Intel GMCH Single Phase PWM Controller RoHS:否 制造商:Texas Instruments 输出端数量:1 拓扑结构:Buck 输出电压:34 V 输出电流: 开关频率: 工作电源电压:4.5 V to 5.5 V 电源电流:600 uA 最大工作温度:+ 125 C 最小工作温度:- 40 C 封装 / 箱体:WSON-8 封装:Reel |
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