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參數資料
| 型號： | MAX1813 |
| 廠商： | Maxim Integrated Products, Inc. |
| 元件分類： | 數字信號處理 |
| 英文描述： | Replaced by TMS320VC5506 : Digital Signal Processors 144-LQFP |
| 中文描述： | 動態(tài)可調、同步降壓型控制器，集成電壓定位電路 |
| 文件頁數： | 17/38頁 |
| 文件大?。?/td> | 738K |
| 代理商： | MAX1813 |
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M
Dynamically-Adjustable, Synchronous Step-Down
Controller with Integrated Voltage Positioning
______________________________________________________________________________________
17
easy design methodology and predictable output volt-
age ripple.
where K is set by the TON pin-strap connection, and
75mV is an approximation to accommodate for the
expected drop across the low-side MOSFET switch and
current-sense resistor (Table 3).
The on-time one-shot has good accuracy at the operat-
ing points specified in the
Electrical Characteristics
table. On-times at operating points far removed from
the conditions specified can vary over a wide range.
For example, the 1000kHz setting will typically run
about 10% slower with inputs much greater than +5V,
due to the very short on-times required.
Although the on-time is set by TON, the input voltage,
and the output voltage, other factors also contribute to
the overall switching frequency. The on-time guaran-
teed in the
Electrical Characteristics
table is influenced
by switching delays in the external high-side MOSFET.
Resistive losses
—
including the inductor, both
MOSFETs, output capacitor ESR, and PC board copper
losses in the output and ground
—
tend to raise the
switching frequency at higher output currents. Switch
dead-time can increase the effective on-time, reducing
the switching frequency. This effect occurs only in
PWM mode (SKP/
SDN
= float) when the inductor cur-
rent reverses at light or negative load currents. With
reversed inductor current, the inductor
’
s EMF causes
LX to go high earlier than normal, extending the on-time
by a period equal to the DH-rising dead-time (26ns
typ).
When the controller operates in continuous
mode, the dead-time is no longer a factor, and the
actual switching frequency is:
where V
DROP1
is the sum of the parasitic voltage drops
in the inductor discharge path, including synchronous
rectifier, inductor, and PC board resistances; V
DROP2
is
the sum of the resistances in the charging path, includ-
ing high-side switch, inductor, and PC board resis-
tances; and t
ON
is the on-time calculated by the
MAX1813.
Automatic Pulse-Skipping Switchover
In skip mode (SKP/
SDN
= high, Table 4), an inherent
automatic switchover to PFM takes place at light
loads (Figure 3). This switchover is controlled by a
comparator that truncates the low-side switch on-time
at the inductor current
’
s zero crossing. This mechanism
causes the threshold between pulse-skipping PFM and
nonskipping PWM operation to coincide with the
boundary between continuous and discontinuous
inductor-current operation. For a 7V to 24V input volt-
age range, this threshold is relatively constant, with
=
+
+
SW
OUT
(V
(V
DROP1
V
ON
IN
DROP1
V
DROP2
V
)
t
)
t
K(V
75mV)
V
ON
OUT
IN
=
+
TON SETTING
(kHz)
K-FACTOR
(
μ
s)
APPROXIMATE
K-FACTOR ERROR
(%)
MINIMUM RECOMMENDED V
BATT
AT V
OUT
= 1.4V (V)
200
300
600
1000
4.9
3.3
1.8
1.05
±
9
±
10
±
13
±
13
1.8
2.0
2.9
3.5
Table 3. Approximate K-Factor Errors
I
I
LOAD
= I
PEAK
/2
ON-TIME
0
TIME
I
PEAK
L
V
BATT
- V
OUT
i
t
=
Figure 3. Pulse-Skipping/Discontinuous Crossover Point
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| MAX182ACPI | Replaced by TMS320BC52 : Digital Signal Processors 100-LQFP -40 to 85 |
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相關代理商/技術參數 |
參數描述 |
|---|---|
| MAX1813EEI | 功能描述:DC/DC 開關控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數量:1 最大工作溫度:+ 125 C 安裝風格: 封裝 / 箱體:CPAK |
| MAX1813EEI+ | 功能描述:DC/DC 開關控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數量:1 最大工作溫度:+ 125 C 安裝風格: 封裝 / 箱體:CPAK |
| MAX1813EEI+T | 功能描述:DC/DC 開關控制器 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 開關頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數量:1 最大工作溫度:+ 125 C 安裝風格: 封裝 / 箱體:CPAK |
| MAX1813EEI-T | 功能描述:DC/DC 開關控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數量:1 最大工作溫度:+ 125 C 安裝風格: 封裝 / 箱體:CPAK |
| MAX1813EVKIT | 功能描述:DC/DC 開關控制器 Evaluation Kit for the MAX1813 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數量:1 最大工作溫度:+ 125 C 安裝風格: 封裝 / 箱體:CPAK |
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