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| 型号： | TPS650241RHBRG4 |
| 厂商： | TEXAS INSTRUMENTS INC |
| 元件分类： | 电源管理 |
| 英文描述： | 2-CHANNEL POWER SUPPLY SUPPORT CKT, PQCC32 |
| 封装： | 5 X 5 MM, GREEN, PLASTIC, QFN-32 |
| 文件页数： | 10/35页 |
| 文件大小： | 955K |
| 代理商： | TPS650241RHBRG4 |
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POWER SAVE MODE OPERATION
I
PFMDCDC1enter +
VINDCDC 1
24 W
I
PFMDCDC2enter +
VINDCDC 2
26 W
I
PFMDCDC3leave +
VINDCDC 3
39 W
(1)
I
PFMDCDC1leave +
VINDCDC 1
18 W
I
PFMDCDC2leave +
VINDCDC 2
20 W
I
PFMDCDC3enter +
VINDCDC 3
29 W
(2)
SLVS774B – JUNE 2007 – REVISED JULY 2009 .............................................................................................................................................................. www.ti.com
During PWM operation the converters use a unique fast response voltage mode controller scheme with input
voltage feed-forward to achieve good line and load regulation allowing the use of small ceramic input and output
capacitors. At the beginning of each clock cycle initiated by the clock signal, the P-channel MOSFET switch is
turned on and the inductor current ramps up until the comparator trips and the control logic turns off the switch.
The current limit comparator also turns off the switch in case the current limit of the P-channel switch is
exceeded. After the adaptive dead time used to prevent shoot through current, the N-channel MOSFET rectifier
is turned on and the inductor current ramps down. The next cycle is initiated by the clock signal again turning off
the N-channel rectifier and turning on the P-channel switch.
The three DC/DC converters operate synchronized to each other, with the VDCDC1 converter as the master. A
180° phase shift between the VDCDC1 switch turn on and the VDCDC2 and a further 90° shift to the VDCDC3
switch turn on decreases the input RMS current and smaller input capacitors can be used. This is optimized for a
typical application where the VDCDC1 converter regulates a Li-Ion battery voltage of 3.7V to 3.3V, the VDCDC2
converter from 3.7V to 2.5V and the VDCDC3 converter from 3.7V to 1.5V.
As the load current decreases, the converters enter Power Save Mode operation. During Power Save Mode the
converters operate in a burst mode (PFM mode) with a frequency between 1.125MHz and 2.25MHz for one burst
cycle. However, the frequency between different burst cycles depends on the actual load current and is typically
far less than the switching frequency, with a minimum quiescent current to maintain high efficiency.
In order to optimize the converter efficiency at light load the average current is monitored and if in PWM mode
the inductor current remains below a certain threshold, then Power Save Mode is entered. The typical threshold
to enter Power Save Mode can be calculated as follows:
During Power Save Mode the output voltage is monitored with a comparator and by maximum skip burst width.
As the output voltage falls below the threshold, set to the nominal VO, the P-channel switch turns on and the
converter effectively delivers a constant current as defined below.
If the load is below the delivered current then the output voltage rises until the same threshold is crossed in the
other direction. All switching activity ceases, reducing the quiescent current to a minimum until the output voltage
has again dropped below the threshold. The power save mode is exited, and the converter returns to PWM mode
if either of the following conditions are met:
1. The output voltage drops 2% below the nominal VO due to increased load current
2. The PFM burst time exceeds 16 × 1/fs (7.1
s typical)
These control methods reduce the quiescent current to typically 14
A per converter and the switching activity to
a minimum thus achieving the highest converter efficiency. Setting the comparator thresholds at the nominal
output voltage at light load current results in a very low output voltage ripple. The ripple depends on the
comparator delay and the size of the output capacitor; increasing capacitor values makes the output ripple tend
to zero. Power Save Mode can be disabled by pulling the MODE pin high. This forces all DC/DC converters into
fixed frequency PWM mode.
18
Copyright 2007–2009, Texas Instruments Incorporated
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| TPS650241RHBT | 功能描述:电池管理 Pwr Mgmt ICs for Li-Ion Powered Sys 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 |
| TPS650241RHBTG4 | 功能描述:电池管理 Pwr Mgmt ICs for Li-Ion Pwred Sys 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 |
| TPS650242RHBR | 功能描述:电池管理 Pwr Mgmt ICs for Li-Ion Powered Sys 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 |
| TPS650242RHBRG4 | 功能描述:电池管理 Pwr Mgmt ICs 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 |
| TPS650242RHBT | 功能描述:电池管理 Pwr Mgmt ICs for Li-Ion Powered Sys 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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