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參數資料
| 型號： | TPS51315RGFR |
| 廠商： | TEXAS INSTRUMENTS INC |
| 元件分類： | 穩壓器 |
| 英文描述： | SWITCHING REGULATOR, 1000 kHz SWITCHING FREQ-MAX, PQCC40 |
| 封裝： | GREEN, PLASTIC, QFN-40 |
| 文件頁數： | 32/32頁 |
| 文件大小： | 1028K |
| 代理商： | TPS51315RGFR |
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UPPER
OUT
LOWER
R
V
1
0.75 V
R
=
+
÷
è
(
)
f
IN
OUT
OUT(LL)
IN
V
1
I
2 L
V
-
=
SLUS881A
– MAY 2009 – REVISED MAY 2011
DETAILED DESCRIPTION
Dual PWM Operations
The primary control loop of the switched-mode power supply (SMPS) functions as an adaptive on-time pulse
width modulation (PWM) controller. It supports a proprietary D-CAP
mode. D-CAP mode uses an internal
compensation circuit and is suitable for a low external component count configuration with an appropriate amount
of equivalent series resistance (ESR) at the output capacitor(s). The output voltage is monitored at a feedback
point voltage.
At the beginning of each cycle, the upper synchronous MOSFET is turned on, or enters the ON state. This
MOSFET is turned off, or enters the OFF state, after an internal one-shot timer expires. This one shot is
determined by the input voltage (VVIN) and the output volage (VOUT) to maintain a relatively constant frequency
over the input voltage range. This is called adaptive on-time control (see PWM Frequency and Adaptive On-Time
Control section). The MOSFET is turned on again when feedback indicates an insufficient output voltage and the
inductor current falls below the overcurrent limit. By repeating the operation in this manner, the controller
regulates the output voltage. The synchronous lower (rectifying) MOSFET is turned on at each OFF state in
order to minimize the conduction losses.
The TPS51315 supports both PWM-Only and Auto-Skip operating modes. When the EN_PSV pin is grounded,
the switcher is disabled. When the EN_PSV pin is connected to a 3.3-V supply or a 5-V supply, Auto-Skip mode
is enabled. The rectifying MOSFET is turned off when the inductor current is zero. This feature enables a
seamless transition to the reduced-frequency operation at light load conditions so that high efficiency is
maintained over a broad range of load currents. When the EN_PSV pin is floated, it is internally pulled up to 1.9
V, and PWM-Only mode is enabled. In this mode, the rectifying MOSFET is not turned off when the inductor
current reaches zero, and so the switching frequency does not change at light load; however the efficiency is
lower in PWM-Only mode than it is in Auto-Skip mode.
The dc output voltage can be set by the external resistor divider as shown in Equation 1.
(1)
Light Load Conditions
When Auto-Skip mode is enabled, the TPS51315 automatically reduces the switching frequency under light load
conditions to maintain high efficiency.
As the output current decreases from a heavy load condition, the inductor current is also reduced and eventually
its valley falls to zero current, which is the boundary between continuous conduction and discontinuous
conduction modes. The rectifying MOSFET is turned off when zero inductor current is detected. As the load
current continues to decrease, the converter runs in discontinuous conduction mode, taking longer to discharge
the output capacitor toward the reference voltage. The on-time maintains the same as when under a heavy load
condition. Alternatively, when the output current increase from light load to heavy load, switching frequency
increases to the preset value as the inductor current reaches the continuous conduction threshold. The transition
load point to the light load operation IOUT(LL) (that is, the threshold between continuous and discontinuous
conduction mode) can be calculated using Equation 2.
where
f is the PWM switching frequency
(2)
Switching frequency versus output current under light load conditions is a function of L,
, VIN and VOUT, but it
decreases almost proportionally to the output current from IOUT(LL) as calculated in Equation 2. For example, it is
approximately 60 kHz at IOUT(LL)/5 when the PWM frequency is 300 kHz.
Copyright
2009–2011, Texas Instruments Incorporated
9
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| TPS51362RVER | 制造商:Texas Instruments 功能描述:22V INPUT, 10A INTEGRATED FET 制造商:Texas Instruments 功能描述:IC REG BUCK SYNC ADJ 10A 28VQFN |
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