- 您现在的位置：买卖IC网 > PDF目录15138 > MAX767EAP+T (Maxim Integrated Products)IC REG CTRLR BUCK PWM CM 20-SSOP PDF资料下载
参数资料
| 型号： | MAX767EAP+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 15/19页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 20-SSOP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,000 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 340kHz |
| 占空比： | 95% |
| 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： | 0°C ~ 70°C |
| 封装/外壳： | 20-SSOP（0.209"，5.30mm 宽） |
| 包装： | 带卷 (TR) |
5V-to-3.3V, Synchronous, Step-Down
Power-Supply Controller
Capacitor ESR Losses
PD CAP = capacitor ESR loss = I RMS 2 x ESR
where I RMS = RMS AC input current, approximately
I LOAD / 2.
Note that losses in the output filter capacitors are small
when the circuit is heavily loaded, because the current
into the capacitor is not chopped. The output capacitor
sees only the small AC sawtooth ripple current. Ensure
that the input bypass capacitor has a ripple current rat-
ing that exceeds the value of I RMS .
IC Supply-Current Losses
PD IC is the quiescent power dissipation of the IC and is
5V times the quiescent supply current (a data sheet
parameter), or about 5mW.
Light-Load Efficiency
Under light loads, the PWM will operate in discontinu-
ous-conduction mode, where the inductor current dis-
charges to zero at some point during each switching
cycle. New loss mechanisms, insignificant at heavy
loads, begin to become important. The basic difference
is that in discontinuous mode, the AC component of the
inductor current is large compared to the load current.
This increases losses in the core and in the output filter
capacitors. Ferrite cores are recommended over pow-
dered-material types for best light-load efficiency.
At light loads, the inductor delivers triangular current
pulses rather than the nearly square waves found in
continuous-conduction mode. These pulses ramp up to
a point set by the idle-mode current comparator, which
is internally fixed at approximately 25% of the full-scale
current-limit level. This 25% threshold provides an opti-
mum balance between low-current efficiency and out-
put voltage noise (the efficiency curve would actually
look better with this threshold set at about 45%, but the
output noise would be too high).
____Additional Application Circuits
High-Accuracy Power Supplies
The standard application circuit’s accuracy is dominat-
ed by reference voltage error (±1.8%) and load regula-
tion error (-2.5%). Both of these parameters can be
improved as shown in Figures 5 and 6. Both circuits
rely on an external integrator amplifier to increase the
DC loop gain in order to reduce the load regulation
error to 0.1%. Reference error is improved in the first
circuit by employing a version of the MAX767 ( “T ”
grade) which has a ±1.2% reference voltage tolerance.
Reference error of the second circuit is further
improved by substituting a highly accurate external ref-
erence chip (MAX872), which contributes ±0.38% total
error over temperature.
These two circuits were designed with the latest gener-
ation of dynamic-clock μPs in mind, which place great
demands on the transient-response performance of the
power supply. As the μP clock starts and stops, the
load current can change by several amps in less than
100ns. This tremendous ? i/ ? t can cause output voltage
overshoot or sag that results in the CPU VCC going out
of tolerance unless the power supply is carefully
designed and located close to the CPU. These circuits
have excellent dynamic response and low ripple, with
transient excursions of less than 40mV under zero to
full-load step change. In particular, these two circuits
support the “VR” (voltage regulator) version of the Intel
P54C Pentium? CPU, which requires that its supply
voltage, including noise and transient errors, be within
the 3.30V to 3.45V range.
To configure these circuits for a given load current
requirement, substitute standard components from
Table 1 for the power switching elements (N1, N2, L1,
C1, C2) or use the Design Procedure . R1 can also be
taken from Table 1, but must be adjusted approximate-
ly 10% higher in order to maintain the correct current-
limit threshold. This increased value is due to the 0.9
gain factor introduced by the H-bridge resistor divider
(R3–R6).
If the remote sense line must sense the output voltage
on the far side of a connector or jumper that has the
possibility of becoming disconnected while the power
supply is operating, an additional 10k ? resistor should
connect the sense line to the output voltage in the con-
nector’s power-supply side in order to prevent acciden-
tal overvoltage at the CPU.
For applications that are powered from a fixed +12V or
battery input rather than from +5V, use a MAX797 IC
instead of the MAX767. The MAX797 is capable of
accepting inputs up to 30V. See the MAX796–MAX799
data sheet for a high-accuracy circuit schematic.
______________________________________________________________________________________
15
相关PDF资料 |
PDF描述 |
|---|---|
| VI-25Z-EX-F3 | CONVERTER MOD DC/DC 2V 30W |
| GBC65DRTH | CONN EDGECARD 130PS DIP .100 SLD |
| VI-25Z-EX-F2 | CONVERTER MOD DC/DC 2V 30W |
| SLP223M016C4P3 | CAP ALUM 22000UF 16V 20% SNAP |
| VI-25Z-EX-F1 | CONVERTER MOD DC/DC 2V 30W |
相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX767EVKIT-SO | 功能描述:DC/DC 开关控制器 Evaluation Kit for the MAX767 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 |
| MAX767RCAP | 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 |
| MAX767RCAP-T | 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 |
| MAX767REAP | 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 |
| MAX767REAP+ | 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 |
发布紧急采购，3分钟左右您将得到回复。