参数资料
型号: TPS81256SIPT
厂商: Texas Instruments
文件页数: 12/26页
文件大小: 0K
描述: IC REG BOOST SYNC 5V 0.6A 9USIP
标准包装: 250
类型: 升压(升压)
输出类型: 固定
输出数: 1
输出电压: 5V
输入电压: 2.5 V ~ 5.5 V
PWM 型: 电流模式
频率 - 开关: 4MHz
电流 - 输出: 600mA
同步整流器:
工作温度: -40°C ~ 85°C
安装类型: *
封装/外壳: *
包装: *
供应商设备封装: *
其它名称: 296-34854-2

SLVSAZ9A – JUNE 2012 – REVISED AUGUST 2013
DETAILED DESCRIPTION
OPERATION
The TPS8125x is a stand-alone, synchronous, step-up converter. The converter operates at a quasi-constant 4-
MHz frequency pulse width modulation (PWM) at moderate to heavy load currents. At light load currents, the
TPS8125x converter operates in power-save mode with pulse frequency modulation (PFM).
During PWM operation, the converter uses a novel quasi-constant on-time valley current mode control scheme to
achieve excellent line/load regulation and allows the use of a small ceramic inductor and capacitors. Based on
the V IN /V OUT ratio, a simple circuit predicts the required on-time.
At the beginning of the switching cycle, the low-side N-MOS switch is turned-on and the inductor current ramps
up to a peak current that is defined by the on-time and the inductance. In the second phase, once the on-timer
has expired, the rectifier is turned-on and the inductor current decays to a preset valley current threshold. Finally,
the switching cycle repeats by setting the on timer again and activating the low-side N-MOS switch.
In general, a dc/dc step-up converter can only operate in "true" boost mode, i.e. the output “boosted” by a certain
amount above the input voltage. The TPS8125x device operates differently as it can smoothly transition in and
out of zero duty cycle operation. Therefore the output can be kept as close as possible to its regulation limits
even though the converter is subject to an input voltage that tends to be excessive. In this operation mode, the
output current capability of the regulator is limited to ca. 150mA. Refer to the typical characteristics section (DC
Output Voltage vs. Input Voltage) for further details.
The current mode architecture with adaptive slope compensation provides excellent transient load response
while requiring only one external tiny capacitor for output filtering and loop stability purposes. Internal soft-start
and loop compensation simplifies the application design process.
POWER-SAVE MODE
The TPS8125X integrates a power-save mode to improve efficiency at light load. In power save mode the
converter only operates when the output voltage trips below a set threshold voltage.
It ramps up the output voltage with several pulses and goes into power save mode once the output voltage
exceeds the set threshold voltage.
The PFM mode is left and PWM mode entered in case the output current can not longer be supported in PFM
mode.
12
Product Folder Links: TPS81256
Copyright ? 2012–2013, Texas Instruments Incorporated
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