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| 型号： | MAX1653EEE-T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 23/28页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 16-QSOP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| PWM 型： | 电流模式，混合 |
| 输出数： | 1 |
| 频率 - 最大： | 350kHz |
| 占空比： | 98% |
| 电源电压： | 4.5 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： | 16-SSOP（0.154"，3.90mm 宽） |
| 包装： | 带卷 (TR) |
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High-Efficiency, PWM, Step-Down
DC-DC Controllers in 16-Pin QSOP
Boost-Supply Diode D2
A 10mA to 100mA Schottky diode or signal diode such
as a 1N4148 works well for D2 in most applications. If
the input voltage can go below 6V, use a Schottky
diode for slightly improved efficiency and dropout char-
acteristics. Don ’t use large power diodes such as
1N5817 or 1N4001, since high junction capacitance
can cause VL to be pumped up to excessive voltages.
Rectifier Diode D3
(Transformer Secondary Diode)
The secondary diode in coupled-inductor applications
must withstand high flyback voltages greater than 60V,
which usually rules out most Schottky rectifiers.
Common silicon rectifiers such as the 1N4001 are also
prohibited, as they are far too slow. This often makes
fast silicon rectifiers such as the MURS120 the only
choice. The flyback voltage across the rectifier is relat-
ed to the V IN -V OUT difference according to the trans-
former turns ratio:
V FLYBACK = V SEC + (V IN - V OUT ) x N
where: N is the transformer turns ratio SEC/PRI
V SEC is the maximum secondary DC output voltage
V OUT is the primary (main) output voltage
Subtract the main output voltage (V OUT ) from V FLYBACK
in this equation if the secondary winding is returned to
V OUT and not to ground. The diode reverse breakdown
rating must also accommodate any ringing due to leak-
age inductance. D3’s current rating should be at least
twice the DC load current on the secondary output.
Table 4. Low-Voltage Troubleshooting
_____________Low-Voltage Operation
Low input voltages and low input-output differential volt-
ages each require some extra care in the design. Low
absolute input voltages can cause the VL linear regula-
tor to enter dropout, and eventually shut itself off. Low
input voltages relative to the output (low V IN -V OUT differ-
ential) can cause bad load regulation in multi-output fly-
back applications. See Transformer Design section.
Finally, low V IN -V OUT differentials can also cause the
output voltage to sag when the load current changes
abruptly. The amplitude of the sag is a function of induc-
tor value and maximum duty factor (D MAX an Electrical
Characteristics parameter, 98% guaranteed over tem-
perature at f = 150kHz) as follows:
(I STEP ) 2 x L
V SAG = ———————————————
2 x C OUT x (V IN(MIN) x D MAX - V OUT )
The cure for low-voltage sag is to increase the value of
the output capacitor. For example, at V IN = 5.5V, V OUT
= 5V, L = 10μH, f = 150kHz, a total capacitance of
660μF will prevent excessive sag. Note that only the
capacitance requirement is increased and the ESR
requirements don ’t change. Therefore, the added
capacitance can be supplied by a low-cost bulk
capacitor in parallel with the normal low-ESR capacitor.
Table 4 summarizes low-voltage operational issues.
SYMPTOM
CONDITION
ROOT CAUSE
SOLUTION
Sag or droop in V OUT
Low V IN -V OUT differential, Limited inductor-current slew
Increase bulk output capacitance per
under step load change
<1V
rate per cycle.
formula above. Reduce inductor value.
Dropout voltage is too
high (V OUT follows V IN as
V IN decreases)
Unstable—jitters between
Low V IN -V OUT differential, Maximum duty-cycle limits
<0.5V exceeded.
Low V IN -V OUT differential, Normal function of internal low-
Reduce f to 150kHz. Reduce MOSFET
on-resistance and coil DCR.
Increase the minimum input voltage or
two distinct duty factors
<0.5V
dropout circuitry.
ignore.
Secondary output won’t
support a load
Not enough duty cycle left to
Low V IN -V OUT differential, initiate forward-mode operation.
V IN < 1.3 x V OUT (main) Small AC current in primary can’t
store energy for flyback operation.
Reduce f to 150kHz. Reduce secondary
impedances—use Schottky if possible.
Stack secondary winding on main output.
High supply current,
poor efficiency
Low input voltage, <5V
VL linear regulator is going into
dropout and isn’t providing
good gate-drive levels.
Use a small 20mA Schottky diode for
boost diode D2. Supply VL from an
external source.
Won’t start under load or
quits before battery is
completely dead
Low input voltage, <4.5V
VL output is so low that it hits the Supply VL from an external source other
VL UVLO threshold at 4.2V max. than V BATT , such as the system 5V supply.
______________________________________________________________________________________
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相关代理商/技术参数 |
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| MAX1653EEE-TG068 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX1653ESE | 功能描述:DC/DC 开关控制器 PWM Step-Down 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 |
| MAX1653ESE+ | 功能描述:DC/DC 开关控制器 PWM Step-Down 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 |
| MAX1653ESE+T | 功能描述:DC/DC 开关控制器 PWM Step-Down 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 |
| MAX1653ESE-T | 功能描述:DC/DC 开关控制器 PWM Step-Down 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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