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参数资料
| 型号： | PTH08T261WAD |
| 厂商： | TEXAS INSTRUMENTS INC |
| 元件分类： | 电源模块 |
| 英文描述： | 1-OUTPUT DC-DC REG PWR SUPPLY MODULE |
| 封装： | ROHS COMPLIAT PACKAGE-10 |
| 文件页数： | 20/38页 |
| 文件大小： | 1206K |
| 代理商： | PTH08T261WAD |
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SLTS272F
– DECEMBER 2006 – REVISED APRIL 2011
Smart Sync Considerations
Operating the PTH08T260W with a low duty cycle may increase the output voltage ripple due to pulse skipping
of the PWM controller. When operating at the nominal switching frequency, input voltages greater than (VO × 11)
may cause the output voltage ripple to increase (typically 2
×).
Synchronizing to a higher frequency and operating with a low duty cycle may impact output voltage ripple. When
operating at 300 kHz, Figure 23 shows the operating region where the output voltage ripple meets the electrical
specifications and the operating region where the output voltage ripple may increase. Figure 24 shows the
operating regions for several switching frequencies. For example, a module operating at 400 kHz and an output
voltage of 1.2 V, the maximum input voltage that meets the output voltage ripple specification is 10 V. Exceeding
10 V may cause in an increase in output voltage ripple. As shown in Figure 24, operating below 6 V allows
operation down to the minimum output voltage over the entire synchronization frequency range without affecting
the output voltage ripple. See the Electrical Characteristics table for the synchronization frequency range limits.
Figure 23. VO Ripple Regions at 300 kHz
(1) (2)
Figure 24. VO Ripple Regions
(1) (2)
(1)
Operation above a given curve may cause the output voltage ripple to increase (typically 2
×).
(2)
When operating at the nominal switching frequency refer to the 300 kHz plot.
Auto-Track
Function
The Auto-Track function is unique to the PTH/PTV family, and is available with all POLA products. Auto-Track
was designed to simplify the amount of circuitry required to make the output voltage from each module power up
and power down in sequence. The sequencing of two or more supply voltages during power up is a common
requirement for complex mixed-signal applications that use dual-voltage VLSI ICs such as the TMS320
DSP
family, microprocessors, and ASICs.
How Auto-Track
Works
Auto-Track works by forcing the module output voltage to follow a voltage presented at the Track control pin (1).
This control range is limited to between 0 V and the module set-point voltage. Once the track-pin voltage is
raised above the set-point voltage, the module output remains at its set-point (2). As an example, if the Track pin
of a 2.5-V regulator is at 1 V, the regulated output is 1 V. If the voltage at the Track pin rises to 3 V, the regulated
output does not go higher than 2.5 V.
When under Auto-Track control, the regulated output from the module follows the voltage at its Track pin on a
volt-for-volt basis. By connecting the Track pin of a number of these modules together, the output voltages follow
a common signal during power up and power down. The control signal can be an externally generated master
ramp waveform, or the output voltage from another power supply circuit (3). For convenience, the Track input
incorporates an internal RC-charge circuit. This operates off the module input voltage to produce a suitable rising
waveform at power up.
Typical Auto-Track
Application
The basic implementation of Auto-Track allows for simultaneous voltage sequencing of a number of Auto-Track
compliant modules. Connecting the Track inputs of two or more modules forces their track input to follow the
same collective RC-ramp waveform, and allows their power-up sequence to be coordinated from a common
Track control signal. This can be an open-collector (or open-drain) device, such as a power-up reset voltage
supervisor IC. See U3 in Figure 25.
To coordinate a power-up sequence, the Track control must first be pulled to ground potential. This should be
done at or before input power is applied to the modules. The ground signal should be maintained for at least
20 ms after input power has been applied. This brief period gives the modules time to complete their internal
soft-start initialization (4), enabling them to produce an output voltage. A low-cost supply voltage supervisor IC,
that includes a built-in time delay, is an ideal component for automatically controlling the Track inputs at power
up.
Figure 25 shows how the TL7712A supply voltage supervisor IC (U3) can be used to coordinate the sequenced
power up of PTH08T260/261W modules. The output of the TL7712A supervisor becomes active above an input
voltage of 3.6 V, enabling it to assert a ground signal to the common track control well before the input voltage
has reached the module's undervoltage lockout threshold. The ground signal is maintained until approximately 28
ms after the input voltage has risen above U3's voltage threshold, which is 10.95 V. The 28-ms time period is
Copyright
2006–2011, Texas Instruments Incorporated
27
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| PTH08T261WAZ | 功能描述:DC/DC转换器 3-A 4.5V-14V Input Cer Cap Vers Non-Iso RoHS:否 制造商:Murata 产品: 输出功率: 输入电压范围:3.6 V to 5.5 V 输入电压（标称）: 输出端数量:1 输出电压（通道 1）:3.3 V 输出电流（通道 1）:600 mA 输出电压（通道 2）: 输出电流（通道 2）: 安装风格:SMD/SMT 封装 / 箱体尺寸: |
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