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參數(shù)資料
| 型號： | MAX1813 |
| 廠商： | Maxim Integrated Products, Inc. |
| 元件分類： | 數(shù)字信號處理 |
| 英文描述： | Replaced by TMS320VC5506 : Digital Signal Processors 144-LQFP |
| 中文描述： | 動態(tài)可調(diào)、同步降壓型控制器，集成電壓定位電路 |
| 文件頁數(shù)： | 24/38頁 |
| 文件大小： | 738K |
| 代理商： | MAX1813 |
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M
Dynamically-Adjustable, Synchronous Step-Down
Controller with Integrated Voltage Positioning
24
______________________________________________________________________________________
Output Overvoltage Protection
The overvoltage protection circuit is designed to pro-
tect the CPU against a shorted high-side MOSFET by
drawing high current and activating the battery
’
s pro-
tection circuit. The output voltage is continuously moni-
tored for overvoltage. If the output exceeds the
overvoltage threshold, the fault protection is triggered
and the circuit shuts down. The DL low-side gate-driver
output latches high, which turns on the synchronous-
rectifier MOSFET with 100% duty and, in turn, rapidly
discharges the output filter capacitor, forcing the output
to ground. If the condition that caused the overvoltage
(such as a shorted high-side MOSFET) persists, the
battery
’
s protection circuit will engage. The MAX1813 is
latched off and won
’
t restart until SKP/
SDN
is toggled
or V
CC
power is cycled.
Overvoltage protection can be defeated using the no-
fault test mode (see
No-Fault Test Mode
).
Output Undervoltage Protection
The output undervoltage protection (UVP) function is
similar to foldback current limiting but employs a timer
rather than a variable current limit. If the MAX1813 out-
put voltage is under 70% of the nominal value, the
PWM is latched off and won
’
t restart until SKP/
SDN
is
toggled or V
CC
power is cycled. To allow startup, UVP
is ignored during the undervoltage fault-blanking time
(the first 256 cycles of the slew rate after startup).
UVP can be defeated using the no-fault test mode (see
No-Fault Test Mode
).
Thermal Fault Protection
The MAX1813 features a thermal fault protection circuit.
When the temperature rises above +160
°
C, the DL low-
side gate-driver output latches high until SKP/
SDN
is
toggled or V
CC
power is cycled. The threshold has
+15
°
C of thermal hysteresis, which prevents the regula-
tor from restarting until the die cools off.
Thermal shutdown can be defeated using the no-fault
test mode (see
No-Fault Test Mode
).
No-Fault Test Mode
The over/undervoltage protection features can compli-
cate the process of debugging prototype breadboards
since there are at most a few milliseconds in which to
determine what went wrong. Therefore, a test mode is
provided to disable the overvoltage protection, under-
voltage protection, and thermal shutdown features, and
clear the fault latch if it has been set. In
“
no-fault
”
test
mode, the regulator operates as if SKP/
SDN
were high
(SKIP mode). Forcing 12V to 15V on SKP/
SDN
activates
no-fault test mode.
Design Procedure
Firmly establish the input voltage range and maximum
load current before choosing a switching frequency
and inductor operating point (ripple-current ratio). The
primary design trade-off lies in choosing a good switch-
ing frequency and inductor operating point, and the fol-
lowing four factors dictate the rest of the design:
Input voltage range:
The maximum value (V
IN(MAX)
)
must accommodate the worst-case high AC-adapter
voltage. The minimum value (V
IN(MIN)
) must account for
the lowest input voltage after drops due to connectors,
fuses, and battery selector switches. If there is a choice
at all, lower input voltages result in better efficiency.
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 selec-
tion, inductor saturation rating, and the design
of the current-limit circuit. The continuous load current
(I
LOAD
) determines the thermal stresses and thus
drives the selection of input capacitors, MOSFETs, and
other critical heat-contributing components. Modern
notebook CPUs generally exhibit I
LOAD
= I
LOAD(MAX)
x
80%.
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 pro-
portional to frequency and V
IN2
. The optimum frequen-
cy is also a moving target, due to rapid improvements
in MOSFET technology that are making higher frequen-
cies more practical.
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 min-
imum practical inductor value is one that causes the
circuit to operate at the edge of critical conduction
(where the inductor current just touches zero with every
cycle at maximum load). Inductor values lower than this
grant no further size-reduction benefit.
The MAX1813
’
s pulse-skipping algorithm initiates skip
mode at the critical-conduction point. Thus, the induc-
tor operating point also determines the load-current
value at which PFM/PWM switchover occurs. The opti-
mum operating point is usually found between 20% and
50% ripple current.
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-
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| MAX182ACPI | Replaced by TMS320BC52 : Digital Signal Processors 100-LQFP -40 to 85 |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX1813EEI | 功能描述:DC/DC 開關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
| MAX1813EEI+ | 功能描述:DC/DC 開關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
| MAX1813EEI+T | 功能描述:DC/DC 開關(guān)控制器 Dynamically Adjustable Synchronous Step-Down Controller w/Integrated Voltage Positioning RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
| MAX1813EEI-T | 功能描述:DC/DC 開關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
| MAX1813EVKIT | 功能描述:DC/DC 開關(guān)控制器 Evaluation Kit for the MAX1813 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
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