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| 型号： | MAX1999EEI+T |
| 厂商： | Maxim Integrated |
| 文件页数： | 29/32页 |
| 文件大小： | 0K |
| 描述： | IC REG QD BCK/LINEAR SYNC 28QSOP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| 拓扑： | 降压（降压）同步（2），线性（LDO）（2） |
| 功能： | 任何功能 |
| 输出数： | 4 |
| 频率 - 开关： | 200kHz ~ 500kHz |
| 电压/电流 - 输出 1： | 控制器 |
| 电压/电流 - 输出 2： | 控制器 |
| 电压/电流 - 输出 3： | 3.3V，100mA |
| 带 LED 驱动器： | 无 |
| 带监控器： | 无 |
| 带序列发生器： | 是 |
| 电源电压： | 4.5 V ~ 24 V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 28-SSOP（0.154"，3.90mm 宽） |
| 供应商设备封装： | 28-QSOP |
| 包装： | 带卷 (TR) |
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High-Efficiency, Quad Output, Main Power-
Supply Controllers for Notebook Computers
Use of Coupled Inductors to Create
Auxiliary Outputs
A coupled inductor or transformer can be substituted for
the inductor in the 5V or 3.3V SMPS to create an auxiliary
output (Figure 12). The MAX1777/MAX1977/MAX1999 are
particularly well suited for such applications because they
can be configured in ultrasonic or forced-PWM mode to
ensure good load regulation when the main supplies are
lightly loaded. An additional postregulation circuit can be
used to improve load regulation and limit output current.
The power requirements of the auxiliary supply must be
considered in the design of the main output. The trans-
former must be designed to deliver the required current
in both the primary and the secondary outputs with the
proper turns ratio and inductance. The power ratings of
the synchronous rectifier MOSFETs and the current limit
in the MAX1777/MAX1977/MAX1999 must also be
adjusted accordingly. Extremes of low input-output dif-
ferentials, widely different output loading levels, and high
turns ratios can further complicate the design due to par-
asitic transformer parameters such as interwinding
capacitance, secondary resistance, and leakage induc-
tance. Power from the main and secondary outputs is
combined to get an equivalent current referred to the
main output. Use this total current to determine the cur-
rent limit (see the Determining the Current Limit section):
I TOTAL = P TOTAL / V OUT
where I TOTAL is the equivalent output current referred
to the main output, and P TOTAL is the sum of the output
power from both the main output and the secondary
output:
usually rules out most Schottky rectifiers. Common sili-
con rectifiers, such as the 1N4001, are also prohibited
because they are too slow. This often makes fast silicon
rectifiers such as the MURS120 the only choice. The fly-
back voltage across the rectifier is related to the V IN -
V OUT difference, according to the transformer turns ratio:
V FLYBACK = V SEC + (V IN - V OUT ) ? N
where N is the transformer turns ratio (secondary wind-
ings/primary windings), V SEC is the maximum secondary
DC output voltage, and V OUT is the primary (main) out-
put voltage. If the secondary winding is returned to V OUT
instead of ground, subtract V OUT from V FLYBACK in the
equation above. The diode’s reverse breakdown voltage
rating must also accommodate any ringing due to leak-
age inductance. The diode’s current rating should be at
least twice the DC load current on the secondary output.
The optional linear postregulator must be selected to
deliver the required load current from the transformer’s
rectified DC output. The linear regulator should be con-
figured to run close to dropout to minimize power dissi-
pation and should have good output accuracy under
those conditions. Input and output capacitors are cho-
sen to meet line regulation, stability, and transient
requirements. There are a wide variety of linear regula-
tors appropriate for this application; consult the specific
linear-regulator data sheet for details.
Widely different output loads effect load regulation. In
particular, when the secondary output is left unloaded
while the main output is fully loaded, the secondary out-
put capacitor may become overcharged by the leakage
inductance, reaching voltages much higher than intend-
ed. In this case, a minimum load or overvoltage protec-
L PRIMARY =
V OUT ( V IN ( MAX ) ? V OUT
V IN ( MAX ) × ? × I TOTAL × LIR
tion may be required on the secondary output to protect
any device connected to this output.
PC Board Layout Guidelines
V SEC + V FWD
N =
V OUT ( MIN ) + V RECT
where L PRIMARY is the primary inductance, N is the
transformer turns ratio, V SEC is the minimum required
rectified secondary voltage, V FWD is the forward drop
across the secondary rectifier, V OUT(MIN) is the minimum
value of the main output voltage, and V RECT is the on-
state voltage drop across the synchronous rectifier
MOSFET. The transformer secondary return is often con-
nected to the main output voltage instead of ground in
order to reduce the necessary turns ratio. In this case,
subtract V OUT from the secondary voltage (V SEC –
V OUT ) in the transformer turns ratio equation above.
The secondary diode in coupled-inductor applications
must withstand flyback voltages greater than 60V, which
Careful PC board layout is critical to achieve minimal
switching losses and clean, stable operation. This is
especially true when multiple converters are on the
same PC board where one circuit can affect the other.
The switching power stages require particular attention
(Figure 13). Refer to the MAX1999 EV kit data sheet for
a specific layout example.
Mount all of the power components on the top side of
the board with their ground terminals flush against one
another, if possible. Follow these guidelines for good
PC board layout:
? Isolate the power components on the top side from
the sensitive analog components on the bottom side
with a ground shield. Use a separate PGND plane
under the OUT3 and OUT5 sides (called PGND3 and
______________________________________________________________________________________
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1999EVKIT | 功能描述:DC/DC 开关控制器 Evaluation Kit for the MAX1777 MAX1977 MAX1999 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 |
| MAX199ACAI | 功能描述:模数转换器 - ADC RoHS:否 制造商:Texas Instruments 通道数量:2 结构:Sigma-Delta 转换速率:125 SPs to 8 KSPs 分辨率:24 bit 输入类型:Differential 信噪比:107 dB 接口类型:SPI 工作电源电压:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-32 |
| MAX199ACAI+ | 功能描述:模数转换器 - ADC 12Bit 8Ch 100ksps 4.18V Precision ADC RoHS:否 制造商:Texas Instruments 通道数量:2 结构:Sigma-Delta 转换速率:125 SPs to 8 KSPs 分辨率:24 bit 输入类型:Differential 信噪比:107 dB 接口类型:SPI 工作电源电压:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-32 |
| MAX199ACAI+T | 功能描述:模数转换器 - ADC 12Bit 8Ch 100ksps 4.18V Precision ADC RoHS:否 制造商:Texas Instruments 通道数量:2 结构:Sigma-Delta 转换速率:125 SPs to 8 KSPs 分辨率:24 bit 输入类型:Differential 信噪比:107 dB 接口类型:SPI 工作电源电压:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-32 |
| MAX199ACAI-T | 功能描述:模数转换器 - ADC RoHS:否 制造商:Texas Instruments 通道数量:2 结构:Sigma-Delta 转换速率:125 SPs to 8 KSPs 分辨率:24 bit 输入类型:Differential 信噪比:107 dB 接口类型:SPI 工作电源电压:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-32 |
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