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參數(shù)資料
| 型號(hào)： | LT1339CSW |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Octal Buffers/Drivers With 3-State Outputs 20-SOIC 0 to 70 |
| 中文描述： | SWITCHING CONTROLLER, 150 kHz SWITCHING FREQ-MAX, PDSO20 |
| 封裝： | 0.300 INCH, PLASTIC, SO-20 |
| 文件頁(yè)數(shù)： | 16/20頁(yè) |
| 文件大?。?/td> | 415K |
| 代理商： | LT1339CSW |
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16
LT1339
APPLICATIO
S I
FOR
ATIO
U
switch gates load the driver outputs such that rise/fall
times exceed about 100ns, buffers can sometimes result
in efficiency gains. Buffers also reduce the effect of back
injection into the bottom side driver output due to coupling
of switch node transitions through the switch FET C
MILLER
.
W
U
U
Paying the Physicists
In high power synchronous buck configurations, certain
physical characteristics of the external MOSFET switches
can impact conversion efficiency. As the input voltage
approaches about 30V, the bottom MOSFETs will begin to
exhibit “phantom turn-on.” This phenomenon is caused
by coupling of the instantaneous voltage step on the
bottom side switch drain through C
MILLER
to the device
gate, yielding internal localized gate-source voltages above
the turn-on threshold of the FET. This generates a shoot-
through blip that ultimately eats away at efficiency num-
bers. In Figure 8 a negative prebias circuit is added to the
bottom side gate. The addition of this
～
3V of negative
offset to the bottom gate drive provides additional off-
state voltage range to prevent phantom turn-on.
This type of prebias circuit is used in the 48V to 5V, 50A
converter pictured in the Typical Applications section.
As currents increase beyond the 10A to 15A range, the
bottom side FET body diode experiences hard turn-on
during switch dead time due to local current loop induc-
tance preventing the timely transfer of charge to the
Schottky catch diode. The charge current required to
commutate this body diode creates a high dV/dt Schottky
avalanche when the diode charge is finally exhausted (due
to an effective inductor current discontinuity at the
moment the body diode no longer requires charge). This
generates an increased turn-on power burst in the topside
switch, causing additional conversion efficiency loss. This
effect of this parasitic inductance can be reduced by using
FETKEY
diodes internal to their packages. FETKEYMOSFETs are
TM
MOSFETs, which have parallel catch Schottky
FETKEYis a trademark of International Rectifier Corporation.
TS
12V
IN
BG
PGND
LT1339
ZTX649
ZTX749
D1N914
1339 F08
10k
1
μ
F
3.3V
Figure 8. Bottom Side Driver Negative Prebias Circuit
not available for high voltages, so as input voltage contin-
ues to increase, they can no longer be used. Because this
necessitates the use of discrete FETs and Schottkys,
interdigitation of a number of smaller devices is required
to minimize parasitic inductances. This technique is also
used in the 48V to 5V, 50A converter shown in the Typical
Applications section.
Optimizing Transient Response—Compensation
Component Values
The dominant compensation point for an LT1339 con-
verter is the V
C
pin (Pin 7), or error amplifier output. This
pin is connected to a series RC network, R
VC
and C
VC
. The
infinite permutations of input/output filtering, capacitor
ESR, input voltage, load current, etc. make for an empirical
method of optimizing loop response for a specific set of
conditions.
Loop response can be observed by injecting a step change
in load current. This can be achieved by using a switchable
load. With the load switching, the transient response of the
output voltage can be observed with an oscilloscope.
Iterating through RC combinations will yield optimized
response. Refer to LTC Application Note 19 in 1990 Linear
Applications Handbook, Volume 1for more information.
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LT1339I | Octal Buffers/Drivers With 3-State Outputs 20-SOIC 0 to 70 |
| LT1339IN | Octal Buffers/Drivers With 3-State Outputs 20-PDIP 0 to 70 |
| LT1339ISW | High Power Synchronous DC/DC Controller |
| LT1341 | 5V RS232 Transceiver with One Receiver Active in Shutdown |
| LT1341C | Octal Buffers/Drivers With 3-State Outputs 20-PDIP 0 to 70 |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LT1339CSW#PBF | 功能描述:IC REG CTRLR BST PWM CM 20-SOIC RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,000 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:1MHz 占空比:50% 電源電壓:9 V ~ 10 V 降壓:無(wú) 升壓:是 回掃:是 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 85°C 封裝/外殼:8-TSSOP（0.173"，4.40mm 寬） 包裝:帶卷 (TR) |
| LT1339CSW#TR | 功能描述:IC REG CTRLR BST PWM CM 20-SOIC RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤(pán) 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
| LT1339CSW#TRPBF | 功能描述:IC REG CTRLR BST PWM CM 20-SOIC RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤(pán) 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
| LT1339CSWPBF | 制造商:Linear Technology 功能描述:DC-DC Controller High Power Synch. SO20W |
| LT1339CSWTRPBF | 制造商:Linear Technology 功能描述: |
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