- 您现在的位置：买卖IC网 > PDF目录16703 > MAX8734AEEI+T (Maxim Integrated Products)IC PWR SUPPLY CONTROLLER 28QSOP PDF资料下载
参数资料
| 型号： | MAX8734AEEI+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 19/33页 |
| 文件大小： | 0K |
| 描述： | IC PWR SUPPLY CONTROLLER 28QSOP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| 应用： | 电源控制器 |
| 输入电压： | 4.5 V ~ 24 V |
| 电流 - 电源： | 25µA |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 28-QSOP |
| 供应商设备封装： | 28-QSOP |
| 包装： | 带卷 (TR) |
第1页第2页第3页第4页第5页第6页第7页第8页第9页第10页第11页第12页第13页第14页第15页第16页第17页第18页当前第19页第20页第21页第22页第23页第24页第25页第26页第27页第28页第29页第30页第31页第32页第33页
High-Efficiency, Quad-Output, Main Power-
Supply Controllers for Notebook Computers
tinuous and discontinuous inductor-current operation
(also known as the critical conduction point):
low-side switch on-time. Disabling the zero-crossing
detector causes the low-side, gate-drive waveform to
2 × L
V +
?
?
I LOAD ( SKIP ) =
K × V OUT _ ? V + ? V OUT _ ?
? ?
become the complement of the high-side, gate-drive
waveform. The inductor current reverses at light loads
as the PWM loop strives to maintain a duty ratio of
V OUT /V+. The benefit of forced-PWM mode is to keep
where K is the on-time scale factor (see the On-Time
One-Shot (t ON ) section). The load-current level at which
PFM/PWM crossover occurs, I LOAD(SKIP) , is equal to 1/2
the peak-to-peak ripple current, which is a function of the
inductor value (Figure 5). For example, in the MAX8732A
Typical Application Circuit with V OUT2 = 5V, V+ = 12V,
L = 7.6μH, and K = 5μs, switchover to pulse-skipping
operation occurs at I LOAD = 0.96A or about 1/5 full load.
The crossover point occurs at an even lower value if a
swinging (soft-saturation) 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-tran-
sient response (especially at low input-voltage levels).
DC output accuracy specifications refer to the trip level of
the error comparator. When the inductor is in continuous
conduction, the output voltage has a DC regulation higher
than the trip level by 50% of the ripple. In discontinuous
conduction ( SKIP = GND, light load), the output voltage
has a DC regulation higher than the trip level by approxi-
mately 1.5% due to slope compensation.
Forced-PWM Mode
The low-noise, forced-PWM ( SKIP = V CC ) mode dis-
ables the zero-crossing comparator, which controls the
the switching frequency fairly constant, but it comes at
a cost: the no-load battery current can be 10mA to
50mA, depending on switching frequency and the
external MOSFETs.
Forced-PWM mode is most useful for reducing audio-
frequency noise, improving load-transient response,
providing sink-current capability for dynamic output
voltage adjustment, and improving the cross-regulation
of multiple-output applications that use a flyback trans-
former or coupled inductor.
Enhanced Ultrasonic Mode
(25kHz (min) Pulse Skipping)
Leaving SKIP unconnected or connecting SKIP to REF
activates a unique pulse-skipping mode with a mini-
mum switching frequency of 25kHz. This ultrasonic
pulse-skipping mode eliminates audio-frequency mod-
ulation that would otherwise be present when a lightly
loaded controller automatically skips pulses. In ultra-
sonic mode, the controller automatically transitions to
fixed-frequency PWM operation when the load reaches
the same critical conduction point (I LOAD(SKIP) ) that
occurs when normally pulse skipping.
An ultrasonic pulse occurs when the controller detects
that no switching has occurred within the last 28μs.
Once triggered, the ultrasonic controller pulls DL high,
turning on the low-side MOSFET to induce a negative
inductor current. After the inductor current reaches the
negative ultrasonic current threshold, the controller
turns off the low-side MOSFET (DL pulled low) and trig-
gers a constant on-time (DH driven high). When the on-
time has expired, the controller reenables the low-side
MOSFET until the controller detects that the inductor
current dropped below the zero-crossing threshold.
Starting with a DL pulse greatly reduces the peak out-
? i
? t
=
V+ - V OUT
L
-I PEAK
put voltage when compared to starting with a DH pulse.
The output voltage at the beginning of the ultrasonic
pulse determines the negative ultrasonic current thresh-
old, resulting in the following equation:
I LOAD = I PEAK / 2
V ISONIC = I L R ON = ( V REF ? V FB ) × 0 . 58
where V FB > V REF and R ON is the on-resistance of the
synchronous rectifier (MAX8734A) or the current-sense
0 ON-TIME
TIME
resistor value (MAX8732A/MAX8733A).
Figure 5. Pulse-Skipping/Discontinuous Crossover Point
______________________________________________________________________________________
19
相关PDF资料 |
PDF描述 |
|---|---|
| 301A048-25/86-0 | BOOT MOLDED |
| V375C36T75B3 | CONVERTER MOD DC/DC 36V 75W |
| EBC40DCMD-S288 | CONN EDGECARD 80POS .100 EXTEND |
| H8MMH-1618M | DIP CABLE - HDM16H/AE16M/HDM16H |
| ELC-09D150DF | COIL CHOKE 15UH RADIAL |
相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX8736BGTL+ | 制造商:Maxim Integrated Products 功能描述:IMPVP 6 CORE SUPPLIES - Rail/Tube |
| MAX8736ETL | 制造商:Maxim Integrated Products 功能描述:IMPVP 6 CORE SUPPLIES - Rail/Tube |
| MAX8736ETL+ | 制造商:Maxim Integrated Products 功能描述:IMPVP 6 CORE SUPPLIES - Rail/Tube |
| MAX8736ETL+T | 制造商:Maxim Integrated Products 功能描述:IMPVP 6 CORE SUPPLIES - Tape and Reel |
| MAX8736ETL-T | 制造商:Maxim Integrated Products 功能描述:IMPVP 6 CORE SUPPLIES - Tape and Reel |
发布紧急采购，3分钟左右您将得到回复。