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| 型号： | MAX8764EEP+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 12/23页 |
| 文件大小： | 0K |
| 描述： | IC CNTRL STP DWN HS 20-QSOP |
| 标准包装： | 2,500 |
| 应用： | 控制器，笔记本电脑电源系统 |
| 输入电压： | 2 V ~ 28 V |
| 输出数： | 1 |
| 输出电压： | 1.8V，2.5V，1 V ~ 5.5 V |
| 工作温度： | 0°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 20-SSOP（0.154"，3.90mm 宽） |
| 供应商设备封装： | 20-QSOP |
| 包装： | 带卷 (TR) |
High-Speed, Step-Down Controller with
Accurate Current Limit for Notebook Computers
Table 3. Operating Mode Truth Table
SHDN
0
SKIP
X
DL
Low
MODE
Shutdown, output UVP fault,
thermal shutdown, UVLO
COMMENTS
Low-power shutdown state. DL is forced to GND. I CC < 1μA typ.
Low-noise operation with no automatic switchover. Fixed-frequency
1
V CC
Switching
Run (PWM), low noise
PWM action is forced regardless of load. Inductor current reverses at
light-load levels. Low noise. High I Q .
1
1
GND
X
Switching
High
Run (PFM/PWM)
Fault
Normal operation with automatic PWM/PFM switchover for pulse
skipping at light loads. Best light-load efficiency.
Fault latch has been set by overvoltage protection. Device remains in
FAULT mode until V CC power is cycled.
Table 4. Frequency Selection Guidelines
FREQUENCY TYPICAL
COMMENTS
(kHz) APPLICATION
easy design methodology and predictable output volt-
age ripple. The on-time is given by:
On-Time = K (V OUT + 0.075V) / V IN
200
TON = V CC
300
TON = Floating
450
TON = REF
600
TON = GND
4-cell Li+ notebook
4-cell Li+ notebook
3-cell Li+ notebook
+5V input
Use for absolute best
efficiency.
Considered mainstream
by current standards.
Useful in 3-cell systems
for lighter loads than the
CPU core or where size is
key.
Good operating point for
compound buck designs
or desktop circuits.
where K (switching period) is set by the TON pin-strap
connection (Table 4), and 0.075V is an approximation to
accommodate for the 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 approximately ±12.5% at 600kHz and 450kHz, and
±10% at the two slower settings. This translates to
reduced switching-frequency accuracy at higher frequen-
cies (Table 5). Switching frequency increases as a func-
tion of load current due to the increasing drop across the
low-side MOSFET, which causes a faster inductor-current
discharge ramp. The on-times guaranteed in the
f =
width is inversely proportional to input voltage and directly
proportional to output voltage. Another one-shot sets a
minimum off-time (400ns typ). The on-time, one-shot is
triggered if the error comparator is low, the low-side switch
current is below the current-limit threshold, and the mini-
mum off-time, one-shot has timed out.
On-Time One-Shot (TON)
The heart of the PWM core is the one-shot that sets the
high-side switch on-time. This fast, low-jitter, adjustable
one-shot includes circuitry that varies the on-time in
response to battery and output voltage. The high-side
switch on-time is inversely proportional to the battery
voltage as measured by the V+ input, and proportional
to the output voltage. This algorithm results in a nearly
constant switching frequency despite the lack of a fixed-
frequency clock generator. The benefits of a constant
switching frequency are twofold: first, the frequency can
be selected to avoid noise-sensitive regions such as the
455kHz IF band; second, the inductor ripple-current
operating point remains relatively constant, resulting in
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 )
12
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX8764ETP | 功能描述:电流型 PWM 控制器 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 |
| MAX8764ETP+ | 功能描述:电流型 PWM 控制器 High-Speed Step Down Controller 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 |
| MAX8764ETP+T | 功能描述:电流型 PWM 控制器 High-Speed Step Down Controller 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 |
| MAX8764ETP-T | 功能描述:电流型 PWM 控制器 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 |
| MAX8765AETI+ | 功能描述:电池管理 Multichemistry Battery Charger RoHS:否 制造商:Texas Instruments 电池类型:Li-Ion 输出电压:5 V 输出电流:4.5 A 工作电源电压:3.9 V to 17 V 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:VQFN-24 封装:Reel |
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