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參數(shù)資料
| 型號(hào)： | LM5035AMH-1 |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SWITCHING CONTROLLER, 2000 kHz SWITCHING FREQ-MAX, PDSO28 |
| 封裝： | TSSOP-28 |
| 文件頁數(shù)： | 14/30頁 |
| 文件大?。?/td> | 585K |
| 代理商： | LM5035AMH-1 |
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T2 = .0007 x R
DLY + 10.01 ns
T1 and T2 can be set to minimum by not connecting a resistor
to DLY, connecting a resistor greater than 300k
from DLY
to ground, or connecting DLY to the REF pin. This may cause
lower than optimal system efficiency if the delays through the
SR signal transformer network, the secondary gate drivers
and the SR MOSFETs are greater than the delay to turn on
the HO or LO MOSFETs. Should an SR MOSFET remain on
while the opposing primary MOSFET is supplying power
through the power transformer, the secondary winding will
experience a momentary short circuit, causing a significant
power loss to occur.
When choosing the R
DLY value, worst case propagation de-
lays and component tolerances should be considered to as-
sure that there is never a time where both SR MOSFETs are
enabled AND one of the primary side MOSFETs is enabled.
The time period T1 should be set so that the SR MOSFET has
turned off before the primary MOSFET is enabled. Converse-
ly, T1 and T2 should be kept as low as tolerances allow to
optimize efficiency. The SR body diode conducts during the
time between the SR MOSFET turns off and the power trans-
former begins supplying energy. Power losses increase when
this happens since the body diode voltage drop is many times
higher than the MOSFET channel voltage drop. The interval
of body diode conduction can be observed with an oscillo-
scope as a negative 0.7V to 1.5V pulse at the SR MOSFET
drain.
UVLO AND OVP VOLTAGE DIVIDER SELECTION FOR R1,
R2, AND R3
Two dedicated comparators connected to the UVLO and OVP
pins are used to detect under-voltage and over-voltage con-
ditions. The threshold value of these comparators, V
UVLO and
V
OVP, is 1.25V (typical). The two functions can be pro-
grammed independently with two voltage dividers from VIN to
AGND as shown in Figure 10 and Figure 11, or with a three-
resistor divider as shown in Figure 12. Independent UVLO
and OVP pins provide greater flexibility for the user to select
the operational voltage range of the system. Hysteresis is ac-
complished by 23 A current sources (I
UVLO and IOVP), which
are switched on or off into the sense pin resistor dividers as
the comparators change state.
When the UVLO pin voltage is below 0.4V, the controller is in
a low current shutdown mode. For a UVLO pin voltage greater
than 0.4V but less than 1.25V the controller is in standby
mode. Once the UVLO pin voltage is greater than 1.25V, the
controller is fully enabled. Two external resistors can be used
to program the minimum operational voltage for the power
converter as shown in Figure 10. When the UVLO pin voltage
falls below the 1.25V threshold, an internal 23 A current sink
is enabled to lower the voltage at the UVLO pin, thus providing
threshold hysteresis. Resistance values for R1 and R2 can
be determined from the following equations.
where V
PWR is the desired turn-on voltage and VHYS is the
desired UVLO hysteresis at V
PWR.
For example, if the LM5035A is to be enabled when V
PWR
reaches 34V, and disabled when VPWR is decreased to 32V,
R1 should be 87 k
, and R2 should be 3.54k. The voltage
at the UVLO pin should not exceed 7V at any time. Be sure
to check both the power and voltage rating (0603 resistors
can be rated as low as 50V) for the selected R1 resistor.
30034129
FIGURE 10. Basic UVLO Configuration
21
www.national.com
LM5035A/LM5035A-1
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參數(shù)描述 |
|---|---|
| LM5035AMH-1/NOPB | 功能描述:電壓模式 PWM 控制器 100V Hb Pwm W/Driver RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
| LM5035AMHX | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:PWM Controller with Integrated Half-Bridge and SyncFET PWM Controller with Integrated Half-Bridge and SyncFET |
| LM5035AMHX/NOPB | 功能描述:電壓模式 PWM 控制器 RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
| LM5035AMHX-1 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:PWM Controller with Integrated Half-Bridge and SyncFET PWM Controller with Integrated Half-Bridge and SyncFET |
| LM5035AMHX-1/NOPB | 功能描述:板上安裝溫度傳感器 RoHS:否 制造商:Omron Electronics 輸出類型:Digital 配置: 準(zhǔn)確性:+/- 1.5 C, +/- 3 C 溫度閾值: 數(shù)字輸出 - 總線接口:2-Wire, I2C, SMBus 電源電壓-最大:5.5 V 電源電壓-最小:4.5 V 最大工作溫度:+ 50 C 最小工作溫度:0 C 關(guān)閉: 安裝風(fēng)格: 封裝 / 箱體: 設(shè)備功能:Temperature and Humidity Sensor |
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