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参数资料
| 型号： | MAX1710EEG |
| 厂商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分类： | 稳压器 |
| 英文描述： | High-Speed, Digitally Adjusted Step-Down Controllers for Notebook CPUs |
| 中文描述： | SWITCHING CONTROLLER, 550 kHz SWITCHING FREQ-MAX, PDSO24 |
| 封装： | 0.150 INCH, 0.025 INCH PITCH, QSOP-24 |
| 文件页数： | 17/28页 |
| 文件大小： | 299K |
| 代理商： | MAX1710EEG |
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17
High-S peed, Digitally Adjusted
S tep-Down Controllers for Notebook CPUs
ry design trade-off lies in choosing a good switching fre-
quency and inductor operating point, and the following
four factors dictate the rest of the design:
1)
Input voltage range
. The maximum value
(V
BATT(MAX)
) must accommodate the worst-case high
AC adapter voltage. The minimum value (V
BATT(MIN)
)
must account for the lowest battery voltage after
drops due to connectors, fuses, and battery selector
switches. If there is a choice at all, lower input volt-
ages result in better efficiency.
2)
Maximum load current
. There are two values to con-
sider. The peak load current(I
LOAD(MAX)
) determines
the instantaneous component stresses and filtering
requirements, and thus drives output capacitor
selection, inductor saturation rating, and the design
of the current-limit circuit. The continuous load cur-
rent (I
LOAD
) determines the thermal stresses and
thus drives the selection of input capacitors,
MOSFETs, and other critical heat-contributing com-
ponents. Modern notebook CPUs generally exhibit
I
LOAD
= I
LOAD(MAX)
·
80%.
3)
Switching frequency
. This choice determines the
basic trade-off between size and efficiency. The opti-
mal frequency is largely a function of maximum input
voltage, due to MOSFET switching losses that are
proportional to frequency and VBATT
2
. The optimum
frequency is also a moving target, due to rapid
improvements in MOSFET technology that are making
higher frequencies more practical (Table 4).
4)
Inductor operating point
. This choice provides
trade-offs between size vs. efficiency. Low inductor
values cause large ripple currents, resulting in the
smallest size, but poor efficiency and high output
noise. The minimum practical inductor value is one
that causes the circuit to operate at the edge of criti-
cal conduction (where the inductor current just touch-
es zero with every cycle at maximum load). Inductor
values lower than this grant no further size-reduction
benefit.
The MAX1710/MAX1711’s pulse-skipping algorithm
initiates skip mode at the critical-conduction point. So,
the inductor operating point also determines the load-
current value at which PFM/PWM switchover occurs.
The optimum point is usually found between 20% and
50% ripple current.
The inductor ripple current also impacts transient-
response performance, especially at low V
BATT
- V
OUT
differentials. Low inductor values allow the inductor cur-
rent to slew faster, replenishing charge removed from the
output filter 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:
I
C
DUTY V
F
BATT MIN
(
2
Inductor Selection
The switching frequency (on-time) and operating point
(% ripple or LIR) determine the inductor value as follows:
V
f LIR I
LOAD MAX
Example: I
LOAD(MAX)
= 7A, V
OUT
= 2V, f = 300kHz, 50%
ripple current or LIR = 0.5.
V
kHz
300
0 5 7
.
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
L
A
=
=
μ
μ
2
1 9
2
(
)
H
H
L
OUT
=
(
)
V
L
V
SAG
LOAD MAX
OUT
=
(
)
)
(
)
(
)
2
BST
+5V
V
BATT
5
DH
LX
MAX1710
MAX1711
Figure 5. Reducing the Switching-Node Rise Time
APPROXIMATELY
-0.65V
1.5mA
V
FORCE
SKIP
GND
MAX1710
MAX1711
Figure 6. Disabling Over/Undervoltage Protection (Test Mode)
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PDF描述 |
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1710EEG.TG068 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX1710EEG.TG074 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX1710EEG+ | 制造商:Maxim Integrated Products 功能描述:LDO CNTRLR STDN 1.25V TO 2V 24QSOP - Rail/Tube |
| MAX1710EEG+T | 制造商:Maxim Integrated Products 功能描述:LDO CNTRLR STDN 1.25V TO 2V 24QSOP - Tape and Reel |
| MAX1710EEG-T | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
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