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參數(shù)資料
| 型號： | MAX1742EEE+T |
| 廠商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 1A/2.7A, 1MHz, Step-Down Regulators with Synchronous Rectification and Internal Switches |
| 中文描述： | 4.7 A SWITCHING REGULATOR, 1000 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封裝： | 0.150 INCH, 0.025 INCH PITCH, QSOP-16 |
| 文件頁數(shù)： | 4/16頁 |
| 文件大小： | 597K |
| 代理商： | MAX1742EEE+T |
MAX1742/MAX1842
1A/2.7A, 1MHz, Step-Down Regulators with
Synchronous Rectification and Internal Switches
12
______________________________________________________________________________________
2) Select the constant off-time as a function of input
voltage, output voltage, and switching frequency.
3) Select RTOFF as a function of off-time.
4) Select the inductor as a function of output voltage,
off-time, and peak-to-peak inductor current.
Setting the Output Voltage
The output of the MAX1742/MAX1842 is selectable
between one of three preset output voltages: 2.5V,
1.8V, and 1.5V. For a preset output voltage, connect FB
to the output voltage and connect FBSEL as indicated
in Table 3. For an adjustable output voltage, connect
FBSEL to GND and connect FB to a resistive divider
between the output voltage and ground (Figure 4).
Regulation is maintained for adjustable output voltages
when VFB = VREF. Use 50k
for R1. R2 is given by the
equation:
where VREF is typically 1.1V.
Programming the Switching Frequency
and Off-Time
The MAX1742/MAX1842 features a programmable
PWM mode switching frequency, which is set by the
input and output voltage and the value of RTOFF, con-
nected from TOFF to GND. RTOFF sets the PMOS
power switch off-time in PWM mode. Use the following
equation to select the off-time according to your
desired switching frequency in PWM mode:
where:
tOFF = the programmed off-time
VIN = the input voltage
VOUT = the output voltage
VPMOS = the voltage drop across the internal
PMOS power switch
VNMOS = the voltage drop across the internal
NMOS synchronous-rectifier switch
fPWM = switching frequency in PWM mode
Select RTOFF according to the formula:
RTOFF = (tOFF - 0.07s) (110k
/ 1.00s)
Recommended values for RTOFF range from 36k
to
430k
for off-times of 0.4s to 4s.
Inductor Selection
The key inductor parameters must be specified: inductor
value (L) and peak current (IPEAK). The following equa-
tion includes a constant, denoted as LIR, which is the
ratio of peak-to-peak inductor AC current (ripple current)
to maximum DC load current. A higher value of LIR allows
smaller inductance but results in higher losses and ripple.
A good compromise between size and losses is found at
approximately a 25% ripple-current to load-current ratio
(LIR = 0.25), which corresponds to a peak inductor cur-
rent 1.125 times the DC load current:
where: IOUT = maximum DC load current
LIR = ratio of peak-to-peak AC inductor current
to DC load current, typically 0.25
L
Vt
I
LIR
OUT
OFF
OUT
=
×
t
VV
V
fV
V
OFF
IN
OUT
PMOS
PWM
IN
PMOS
NMOS
–
=
()
+
()
R2
R1
V
1
OUT
REF
=
Figure 4. Adjustable Output Voltage
PIN
2.5
VCC
Output voltage
1.5
1.8
REF
Output voltage
Adjustable
GND
Resistive
divider
FB
OUTPUT
VOLTAGE
(V)
FBSEL
Unconnected
Output voltage
Table 3. Output Voltage Programming
LX
R2
R1
R1 = 50k
R2 = R1(VOUT / VREF - 1)
VREF = 1.1V
FB
VOUT
MAX1742
MAX1842
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| MAX17434GTL+ | 制造商:Maxim from Components Direct 功能描述:THE MAXIM MAX17434GTL+ IS A PWM REGULATOR. - Rail/Tube 制造商:Maxim 功能描述:The Maxim MAX17434GTL+ is a PWM Regulator. |
| MAX17435ETG+ | 功能描述:電池管理 High f SMBus Battery Charger RoHS:否 制造商:Texas Instruments 電池類型:Li-Ion 輸出電壓:5 V 輸出電流:4.5 A 工作電源電壓:3.9 V to 17 V 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:VQFN-24 封裝:Reel |
| MAX17435ETG+T | 功能描述:電池管理 High f SMBus Battery Charger RoHS:否 制造商:Texas Instruments 電池類型:Li-Ion 輸出電壓:5 V 輸出電流:4.5 A 工作電源電壓:3.9 V to 17 V 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:VQFN-24 封裝:Reel |
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