- 您现在的位置：买卖IC网 > PDF目录97995 > L5994A (STMICROELECTRONICS) 1 A DUAL SWITCHING CONTROLLER, 345 kHz SWITCHING FREQ-MAX, PQFP32 PDF资料下载
参数资料
| 型号： | L5994A |
| 厂商： | STMICROELECTRONICS |
| 元件分类： | 稳压器 |
| 英文描述： | 1 A DUAL SWITCHING CONTROLLER, 345 kHz SWITCHING FREQ-MAX, PQFP32 |
| 封装： | TQFP-32 |
| 文件页数： | 8/26页 |
| 文件大小： | 322K |
| 代理商： | L5994A |
Obsolete
Product(s)
- Obsolete
Product(s)
L5994 - L5994A
16/26
Power MOSFET's and Schottky Diodes
Since the gate drivers of the device are powered by a 5V bus , the use of logic-level MOSFET's is highly rec-
ommended, especially for high current applications. Their breakdown voltage V(BR)DSS must be greater than
VINMAX with a certain margin, so the selection will address 20V or 30V devices.
The RDS(ON) can be selected once the allowable power dissipation has been established. By selecting identical
power MOSFET's as the main switch and the synchronous rectifier, the total power they dissipate does not de-
pend on the duty cycle. Thus, if PON is this power loss (few percent of the rated output power), the required
RDS(ON) (@ 25 °C) can be derived from:
where Iout is either ITOT5 or IOUT3, according to the section under consideration, a is the temperature coefficient
of RDS(ON) (typically, a = 5 10
-3 °C-1 for these low-voltage classes) and
T the admitted temperature rise. It is
worth noticing, however, that generally the lower RDS(ON), the higher is the gate charge Qg, which leads to a
higher gate drive consumption. In fact, each switching cycle, a charge Qg moves from the input source to
ground, resulting in an equivalent drive current:
Ig = Qg fSW
which affects efficiency at low load currents. Besides, this current is drawn from the PREG5 line whose source
capability, ISRC (25mA min), must not be exceeded, thus a further constraint concernes the MOSFET total gate
charge (@VGS = 5V):
assuming four identical MOSFET's.
The Schottky diode to be placed in parallel to the synchronous rectifier must have a reverse voltage VRRM great-
er than VINMAX. Since it conducts for less than 5% of the switching period, the current rating can be much lower
than Iout. The selection criterion should be:
Vt(Schottky) < Vt(body-diode)@I = ILPK
Sense Resistors
The sense resistor of each section is selected according to their respective maximum output current. The cur-
rent sense comparator limits the inductor peak current and therefore the maximum DC output current is the peak
value less half of the peak-to-peak ripple. The intervention threshold is set at 50mV for both sections, thus the
resistor values should be:
Since the comparator threshold that triggers pulse-skipping mode is 11mV, the output current at which the sys-
tem enters this kind of operation is approximately one fourth of the maximum output current. The sense resistors
values are in the low milliohms thus it is important to take correctly the current sense signals. Make sure that
the Kelvin connections between the current sense pins of the IC and the sense resistor do not carry the output
current.
R
DS ON
()
P
ON
I
OUT
2
1
α
T
+
()
-----------------------------------------------
=
Q
g
I
SRC
4f
SW
-----------------
≤
R
SENSE5
50
I
L5 PK
-------------- m
[]
R
SENSE 5
50
I
L5 PK
-------------- m
[]
–
=
相关PDF资料 |
PDF描述 |
|---|---|
| L5994 | 1 A DUAL SWITCHING CONTROLLER, 345 kHz SWITCHING FREQ-MAX, PQFP32 |
| L6206PD013TR | STEPPER MOTOR CONTROLLER, 5.6 A, PDSO36 |
| L6207PD013TR | STEPPER MOTOR CONTROLLER, 5.6 A, PDSO36 |
| L6219DSA | STEPPER MOTOR CONTROLLER, 1 A, PDSO24 |
| L6228PDTR | STEPPER MOTOR CONTROLLER, 2.8 A, PDSO36 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| L5995 | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Current-Mode SMPS Controller |
| L5996 | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:5 BIT DYNAMIC DAC CONTROLLER FOR MOBILE CPU |
| L-59BL/1EGW | 制造商:Kingbright Corporation 功能描述: 制造商:Kingbright Corporation 功能描述:LED 5MM RED/GREEN 40MCD/60MCD 制造商:Kingbright Corporation 功能描述:LED, 5MM, RED/GREEN, 40MCD/60MCD 制造商:Kingbright Corporation 功能描述:LED, 5MM, RED/GREEN, 40MCD/60MCD, LED Colour:Red, Green, Height:7.24mm, Width:7. 制造商:Kingbright Corporation 功能描述:Red/grn r/a cbi,5mm,L-59BL/1EGW |
| L-59BL/1EYW | 制造商:Kingbright Corporation 功能描述: 制造商:Kingbright Corporation 功能描述:LED 5MM RED/YELLOW 40MCD/40MCD 制造商:Kingbright Corporation 功能描述:LED, 5MM, RED/YELLOW, 40MCD/40MCD 制造商:Kingbright Corporation 功能描述:LED, 5MM, RED/YELLOW, 40MCD/40MCD, LED Colour:Red, Yellow, Height:7.24mm, Width: |
| L-59BL/1GEW | 制造商:Kingbright Corporation 功能描述: |
发布紧急采购，3分钟左右您将得到回复。