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| 型号： | MAX1631EAI |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 22/29页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 28-SSOP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 46 |
| PWM 型： | 电流模式，混合 |
| 输出数： | 2 |
| 频率 - 最大： | 330kHz |
| 占空比： | 99% |
| 电源电压： | 4.2 V ~ 30 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | 28-SSOP（0.209"，5.30mm 宽） |
| 包装： | 管件 |
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Multi-Output, Low-Noise Power-Supply
Controllers for Notebook Computers
Table 5. Low-Voltage Troubleshooting Chart
SYMPTOM
CONDITION
ROOT CAUSE
SOLUTION
Increase bulk output capacitance
Sag or droop in V OUT under
step-load change
Low V IN -V OUT
differential, <1.5V
Limited inductor-current
slew rate per cycle.
per formula (see Low-Voltage
Operation section). Reduce inductor
value.
Dropout voltage is too high
(V OUT follows V IN as V IN
decreases)
Unstable—jitters between
different duty factors and
frequencies
Secondary output won’t
support a load
Poor efficiency
Won’t start under load or
quits before battery is
completely dead
Low V IN -V OUT
differential, <1V
Low V IN -V OUT
differential, <0.5V
Low V IN -V OUT
differential,
V IN < 1.3 x V OUT (main)
Low input voltage, <5V
Low input voltage, <4.5V
Maximum duty-cycle limits
exceeded.
Normal function of internal
low-dropout circuitry.
Not enough duty cycle left
to initiate forward-mode
operation. Small AC current
in primary can’t store ener-
gy for flyback operation.
VL linear regulator is going
into dropout and isn’t provid-
ing good gate-drive levels.
VL output is so low that it
hits the VL UVLO threshold.
Reduce operation to 200kHz.
Reduce MOSFET on-resistance and
coil DCR.
Increase the minimum input voltage
or ignore.
Reduce operation to 200kHz.
Reduce secondary impedances;
use a Schottky diode, if possible.
Stack secondary winding on the
main output.
Use a small 20mA Schottky diode
for boost diode D2. Supply VL from
an external source.
Supply VL from an external source
other than V IN , such as the system
+5V supply.
PD(tran) = transition loss = V IN xI LOAD x f x x
[ (V IN RSS GATE ) + 20ns ]
P TOTAL = P(I R) + P(tran) + P(gate) +
P = (I R) = (I LOAD ) x (R DC DS(ON) SENSE )
+ R + R
________________Applications Information
Heavy-Load Efficiency Considerations
The major efficiency-loss mechanisms under loads are,
in the usual order of importance:
? P(I 2 R) = I 2 R losses
? P(tran) = transition losses
? P(gate) = gate-charge losses
? P(diode) = diode-conduction losses
? P(cap) = capacitor ESR losses
? P(IC) = losses due to the IC ’s operating supply
supply current
Inductor core losses are fairly low at heavy loads
because the inductor’s AC current component is small.
Therefore, they aren’t accounted for in this analysis.
Ferrite cores are preferred, especially at 300kHz, but
powdered cores, such as Kool-Mu, can work well.
Efficiency = P OUT / P IN x 100%
= P OUT / (P OUT + P TOTAL ) x 100%
2
P(diode) + P(cap) + P(IC)
2 2
where R DC is the DC resistance of the coil, R DS(ON) is
the MOSFET on-resistance, and R SENSE is the current-
sense resistor value. The R DS(ON) term assumes identi-
cal MOSFETs for the high-side and low-side switches,
because they time-share the inductor current. If the
MOSFETs aren’t identical, their losses can be estimat-
ed by averaging the losses according to duty factor.
3
2
xC /I
where C RSS is the reverse transfer capacitance of the
high-side MOSFET (a data-sheet parameter), I GATE is the
DH gate-driver peak output current (1.5A typical), and
20ns is the rise/fall time of the DH driver (20ns typical).
P(gate) = qG x f x VL
where VL is the internal-logic-supply voltage (+5V), and qG
is the sum of the gate-charge values for low-side and high-
side switches. For matched MOSFETs, qG is twice the
data-sheet value of an individual MOSFET. If V OUT is set to
less than 4.5V, replace VL in this equation with V BATT . In
this case, efficiency can be improved by connecting VL to
an efficient 5V source, such as the system +5V supply.
P(diode) = diode - conduction losses
= I LOAD x V FWD x t D x f
22
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| MAX1631EAI+ | 功能描述:DC/DC 开关控制器 Multi-Out Low-Noise Power-Supply Ctlr RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX1631EAI+T | 功能描述:DC/DC 开关控制器 Multi-Out Low-Noise Power-Supply Ctlr RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX1631EAI-T | 功能描述:DC/DC 开关控制器 RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX1631EAI-TG074 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX1631EVKIT-SO | 功能描述:DC/DC 开关控制器 Evaluation Kit for the MAX1630 MAX1631 MAX1632 RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
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