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參數(shù)資料
| 型號： | MAX758ACWE |
| 廠商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 10-Line To 4-Line And 8-Line To 3-Line Priority Encoders 20-LCCC -55 to 125 |
| 中文描述： | 2 A SWITCHING REGULATOR, 190 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封裝： | PLASTIC, SOP-16 |
| 文件頁數(shù)： | 9/16頁 |
| 文件大?。?/td> | 206K |
| 代理商： | MAX758ACWE |
tors’ leakage currents rises sharply. The actual design
limit for standby current is much less than the 100μA
specified in the Electrical Characteristics (see the
Standby Current vs. Temperature graph in the Typical
Operating Characteristics). However, testing to tighter
limits is prohibitive because the current takes several
seconds to settle to a final value. For normal operation,
connect
SHDN
to V+. Coming out of shutdown mode
initiates a soft-start cycle.
Continuous-/Disc ontinuous-
Conduc tion Modes
The input voltage, output voltage, load current, and
inductor value determine whether the IC operates in
continuous or discontinuous mode. As the inductor
value or load current decreases, or the input voltage
increases, the MAX750A/MAX758A tend to operate in
discontinuous-conduction mode (DCM). In DCM, the
inductor-current slope is steep enough so it decays to
zero before the end of the transistor off-time. In contin-
uous-conduction mode (CCM), the inductor current
never decays to zero, which is typically more efficient
than DCM. CCM allows the MAX750A/MAX758A to
deliver maximum load current, and is also slightly less
noisy than DCM because the ripple current in the out-
put capacitor is smaller.
Internal Referenc e
The +1.23V bandgap reference supplies up to 100μA
at REF. Connect a 0.01μF bypass capacitor from REF
to GND.
Osc illator
The internal oscillator of the MAX750A typically oper-
ates at 170kHz (160kHz for the MAX758A). The Typical
Operating Characteristics indicate stability of the oscil-
lator frequency over temperature and supply voltage.
__________Applic ations Information
Figure 3 shows the MAX750A/MAX758A configured for a
standard 5V step-down application. Table 2 lists the com-
ponents for the desired operating temperature range.
These circuits are useful in systems that require high cur-
rent at high efficiency and are powered by an unregulated
supply, such as a battery or wall-plug AC-DC transformer.
They will operate over the entire line, load, and tempera-
ture ranges using the single set of component values
shown in Figure 3 and listed in Table 2.
Induc tor S elec tion
The MAX750A/MAX758A require no inductor design
because they are tested in-circuit, and are guaranteed
to deliver the power specified in the Electrical
Characteristics with high efficiency using a single
100μH (MAX75_AC) or 33μH (MAX75_AE/AM) inductor
The inductor’s incremental saturation-current rating
should be greater than 1A, and its DC resistance
should be less than 0.8
. Table 2 lists inductor types
and suppliers for various applications. The surface-
mount inductors and the larger-size through-hole
inductors have nearly equivalent efficiencies.
Adjusting the Output V oltage
The MAX750A/MAX758A have outputs adjustable from
1.25V to the input voltage. To set the output voltage,
connect a voltage divider to the feedback input pin
(CC) as shown in Figure 3. The output voltage is set by
R2 and R3 as follows:
Let R3 be any resistance in the 10k
to 20k
range
(typically 10k
), then
R2 = R3 [((V
OUT
/1.22V) - 1)]
Output tolerance over temperature is ±4.5% plus exter-
nal resistor tolerances.
Output Filter Capac itor S elec tion
The primary criterion for selecting the output filter
capacitor is low equivalent series resistance (ESR).
The product of the inductor-current variation and the
ESR of the output capacitor determines the amplitude
of the sawtooth ripple seen on the output voltage. In
addition, the ESR of the output filter capacitor should
be minimized to maintain AC stability. The ESR of the
capacitor should be less than 0.25
to keep the output
ripple less than 50mVp-p over the entire current range
(using a 100μH inductor). Capacitor ESR ususally rises
M
Adjustable, S tep-Down,
Current-Mode PWM Regulators
_______________________________________________________________________________________
9
SS
MAX750A
MAX758A
SS CLAMP
1M
±35%
1.23V
R1
510k
C1
FROM SHDN
Figure 2. Block Diagram of Soft-Start Circuitry
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX758ACWE+ | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 Adjustable PWM Step-Down Regulator RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開關(guān)頻率:1.5 MHz 輸出電壓:0.5 V to 0.86 V 輸出電流:4 A 輸出端數(shù)量: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5 |
| MAX758ACWE+T | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 Adjustable PWM Step-Down Regulator RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開關(guān)頻率:1.5 MHz 輸出電壓:0.5 V to 0.86 V 輸出電流:4 A 輸出端數(shù)量: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5 |
| MAX758ACWE-T | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開關(guān)頻率:1.5 MHz 輸出電壓:0.5 V to 0.86 V 輸出電流:4 A 輸出端數(shù)量: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5 |
| MAX758ACWE-TG068 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX758AEPA | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 Adjustable PWM Step-Down Regulator RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開關(guān)頻率:1.5 MHz 輸出電壓:0.5 V to 0.86 V 輸出電流:4 A 輸出端數(shù)量: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5 |
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