參數(shù)資料
型號(hào)： DS232AS
廠(chǎng)商： DALLAS SEMICONDUCTOR
元件分類(lèi)： Line Driver or Receiver
英文描述： LINE TRANSCEIVER, PDSO16
封裝： 0.300 INCH, SOIC-16
文件頁(yè)數(shù)： 10/28頁(yè)
文件大小： 581K
代理商： DS232AS
MAX15023
Wide 4.5V to 28V Input, Dual-Output
Synchronous Buck Controller
18
Maxim Integrated
Setting the Cycle-by-Cycle, Low-Side,
Source Peak Current Limit
The minimum current-limit threshold must be high
enough to support the maximum expected load current
with the worst-case low-side MOSFET on-resistance
value since the low-side MOSFET’s on-resistance is
used as the current-sense element. The inductor’s
cycle-by-cycle, low-side, source peak current occurs at
ILOAD(MAX) minus half the ripple current. The ripple cur-
rent is maximum when the inductor value is at the lower
limit of its specified tolerance. The minimum value of
the current-limit threshold voltage (VITH) should be
greater than the voltage on the low-side MOSFET dur-
ing the ripple-current valley:
where RDS(ON) is the on-resistance of the low-side
MOSFET in ohms. Use the maximum value for RDS(ON)
from the low-side MOSFET’s data sheet.
To adjust the current-limit threshold, connect a resistor
(RLIM_) from LIM_ to SGND. The relationship between
the current-limit threshold (VITH_) and RLIM_ is:
where RLIM_ is in k and VITH_ is in mV.
An RLIM_ resistance range of 6k to 60k corresponds
to a current-limit threshold of 30mV to 300mV. When
adjusting the current limit, use 1% tolerance resistors to
minimize errors in the current-limit threshold setting.
Input Capacitor
The input filter capacitor reduces peak currents drawn
from the power source and reduces noise and voltage
ripple on the input caused by the circuit’s switching.
The two converters of the MAX15023 run 180° out-of-
phase, thereby, effectively doubling the switching fre-
quency at the input and lowering the input RMS current.
The input ripple waveform would be unsymmetrical due
to the difference in load current and duty cycle between
converter 1 and converter 2. In fact, the worst-case input
RMS current occurs when only one controller is operat-
ing. The converter delivering the highest output power
(VOUT x IOUT) must be used in the formulas below:
The input capacitor RMS current requirement (IRMS) is
defined by the following equation:
IRMS has a maximum value when the input voltage
equals twice the output voltage (VIN = 2VOUT), so
IRMS(MAX) = ILOAD(MAX)/2.
Choose an input capacitor that exhibits less than +10°C
temperature rise at the RMS input current for optimal
long-term reliability.
The input voltage ripple is composed of
VQ (caused
by the capacitor discharge) and
VESR (caused by the
ESR of the capacitor). Use low-ESR ceramic capacitors
with high ripple current capability at the input. Assume
the contribution from the ESR and capacitor discharge
are equal to 50%. Calculate the input capacitance and
ESR required for a specified input voltage ripple using
the following equations:
where:
and:
where:
All equations listed above are valid under the assump-
tion that the input ports of both converters can be
merged in the physical layout, so that only one input
capacitor truly serves both converters. If this is not the
case, additional low-ESR, low-ESL ceramic capacitors
should be locally placed on each converter’s input port,
connected between the drain of the high-side MOSFET
and the source of the low-side MOSFET.
Output Capacitor
The key selection parameters for the output capacitor
are capacitance value, ESR, and voltage rating. These
parameters affect the overall stability, output ripple volt-
age, and transient response. The output ripple has two
components: variations in the charge stored in the out-
put capacitor, and the voltage drop across the capaci-
tor’s ESR caused by the current flowing into and out of
the capacitor:
VV
V
RIPPLE
ESR
Q
+
D
V
OUT
IN
=
C
ID
D
Vf
IN
OUT
QSW
=
×
()
1
I
VV
V
Vf
L
IN
OUT
IN
SW
=
×
××
()
ESR
V
I
IN
ESR
OUT
L
=
+
2
II
VV
V
RMS
LOAD MAX
OUT
IN
OUT
IN
=
()
R
V
A
LIM
ITH
_
=
×
10
50
VR
I
LIR
ITH
DS ON MAX
LOAD MAX
>×
×
(,
)
(
)
1
2
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
DS232AS/T&R 制造商:Maxim Integrated Products 功能描述:IC TXRX DUAL RS-232 5V 16-SOIC
DS232AS/T&R 功能描述:RS-232接口集成電路 RoHS:否 制造商:Exar 數(shù)據(jù)速率:52 Mbps 工作電源電壓:5 V 電源電流:300 mA 工作溫度范圍:- 40 C to + 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:LQFP-100 封裝:
DS232AS+ 功能描述:RS-232接口集成電路 Dual RS-232 Transmitter/Receiver RoHS:否 制造商:Exar 數(shù)據(jù)速率:52 Mbps 工作電源電壓:5 V 電源電流:300 mA 工作溫度范圍:- 40 C to + 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:LQFP-100 封裝:
DS232AS+T&R 制造商:Maxim Integrated Products 功能描述:IC TXRX DUAL RS-232 5V 16-SOIC
DS232AS+T&R 功能描述:RS-232接口集成電路 RoHS:否 制造商:Exar 數(shù)據(jù)速率:52 Mbps 工作電源電壓:5 V 電源電流:300 mA 工作溫度范圍:- 40 C to + 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:LQFP-100 封裝:
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