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| 型号： | MAX1714BEEE+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 12/24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 |
| 输出数： | 1 |
| 频率 - 最大： | 600kHz |
| 占空比： | 100% |
| 电源电压： | 4.5 V ~ 5.5 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) |
High-Speed Step-Down Controller
for Notebook Computers
where K is set by the TON pin-strap connection and
0.075V is an approximation to accommodate for the
duty-cycle applications, this threshold is relatively con-
stant, with only a minor dependence on battery voltage.
expected drop across the low-side MOSFET switch.
One-shot timing error increases for the shorter on-time
settings due to fixed propagation delays; it is approxi-
I LOAD(SKIP) ≈
KV OUT
2L
?
V IN - V OUT
V IN
f =
mately ±12.5% at 600kHz and 450kHz, and ±10% at the
two slower settings. This translates to reduced switching-
frequency accuracy at higher frequencies (Table 5).
Switching frequency increases as a function of load cur-
rent due to the increasing drop across the low-side
MOSFET, which causes a faster inductor-current dis-
charge ramp. The on-times guaranteed in the Electrical
Characteristics are influenced by switching delays in the
external high-side power MOSFET.
Two external factors that influence switching-frequency
accuracy are resistive drops in the two conduction loops
(including inductor and PC board resistance) and the
dead-time effect. These effects are the largest contribu-
tors to the change of frequency with changing load cur-
rent. The dead-time effect increases the effective
on-time, reducing the switching frequency as one or
both dead times are added to the effective on-time. It
occurs only in PWM mode ( SKIP = high) when the induc-
tor current reverses at light or negative load currents.
With reversed inductor current, the inductor’s EMF caus-
es LX to go high earlier than normal, extending the on-
time by a period equal to the low-to-high dead time.
For loads above the critical conduction point, the actual
switching frequency is:
V OUT + V DROP1
t ON (V IN + V DROP2 )
where V DROP1 is the sum of the parasitic voltage drops
in the inductor discharge path, including synchronous
rectifier, inductor, and PC board resistances; V DROP2 is
the sum of the resistances in the charging path, and t ON
is the on-time calculated by the MAX1714.
Automatic Pulse-Skipping Switchover
In skip mode ( SKIP low), an inherent automatic
switchover to PFM takes place at light loads. This
switchover is effected by a comparator that truncates the
low-side switch on-time at the inductor current’s zero
crossing. This mechanism causes the threshold between
pulse-skipping PFM and nonskipping PWM operation to
coincide with the boundary between continuous and dis-
continuous inductor-current operation (also known as the
“critical conduction ” point; see the Continuous to
Discontinuous Inductor Current Point vs. Input Voltage
graph in the Typical Operating Characteristics ). In low-
where K is the on-time scale factor (Table 5). The load-
current level at which PFM/PWM crossover occurs,
I LOAD( SKIP ) , is equal to 1/2 the peak-to-peak ripple cur-
rent, which is a function of the inductor value (Figure 3).
For example, in the standard application circuit with
K = 3.3μs (Table 5), V OUT = 2.5V, V IN = 15V, and L =
6.8μH, switchover to pulse-skipping operation occurs at
I LOAD = 0.51A or about 1/8 full load. The crossover point
occurs at an even lower value if a swinging (soft-satura-
tion) inductor is used.
The switching waveforms may appear noisy and asyn-
chronous when light loading causes pulse-skipping
operation, but this is a normal operating condition that
results in high light-load efficiency. Trade-offs in PFM
noise vs. light-load efficiency are made by varying the
inductor value. Generally, low inductor values produce a
broader efficiency vs. load curve, while higher values
result in higher full-load efficiency (assuming that the coil
resistance remains fixed) and less output voltage ripple.
Penalties for using higher inductor values include larger
physical size and degraded load-transient response
(especially at low input voltage levels).
DC output accuracy specifications refer to the error-com-
parator threshold of the error comparator. When the
inductor is in continuous conduction, the output voltage
will have a DC regulation level higher than the trip level
by 50% of the ripple. In discontinuous conduction ( SKIP
= AGND, light-loaded), the output voltage will have a DC
regulation level higher than the error-comparator thresh-
old by approximately 1.5% due to slope compensation.
Forced-PWM Mode ( SKIP = High)
The low-noise forced-PWM mode ( SKIP = high) disables
the zero-crossing comparator, which controls the low-
side switch on-time. This causes the low-side gate-drive
waveform to become the complement of the high-side
gate-drive waveform. This in turn causes the inductor
current to reverse at light loads while DH maintains a
duty factor of V OUT /V IN . The benefit of forced-PWM
mode is to keep the switching frequency fairly constant,
but it comes at a cost: the no-load battery current can be
10mA to 40mA, depending on the external MOSFETs.
Forced-PWM mode is most useful for reducing audio-
frequency noise, improving load-transient response, pro-
viding sink-current capability for dynamic output voltage
adjustment, and improving the cross-regulation of
12
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1714BEEE-TG074 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX1714BEVKIT | 功能描述:电流型 PWM 控制器 Evaluation Kit for the MAX1714B RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MAX1715EEI | 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 |
| MAX1715EEI+ | 功能描述:DC/DC 开关控制器 Dual Step-Down Controller 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 |
| MAX1715EEI+T | 功能描述:DC/DC 开关控制器 Dual Step-Down Controller 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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