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参数资料
| 型号： | MAX1954AEUB+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 13/18页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 10-UMAX |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 360kHz |
| 占空比： | 93% |
| 电源电压： | 3 V ~ 13.2 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | 10-TFSOP，10-MSOP（0.118"，3.00mm 宽） |
| 包装： | 带卷 (TR) |
Low-Cost, Current-Mode PWM Buck
Controller with Foldback Current Limit
( )
V VALLEY = R DS ( ON ) × ( I LOAD ( MAX ) ? ? ? × I LOAD MAX
P N 1 CC = ? OUT ? × I 2 LOAD × R DS ( ON )
choose the high-side MOSFET (N1) that has conduction
losses equal to switching loss at nominal input voltage
and output current. The selected MOSFETs must have an
R DS(ON) that satisfies the current-limit setting condition
above. For N2, ensure that it does not spuriously turn on
due to dV/dt caused by N1 turning on, as this would
result in shoot-through current degrading the efficiency.
MOSFETs with a lower Q gd /Q gs ratio have higher immuni-
ty to dV/dt.
For proper thermal-management design, the power dis-
sipation must be calculated at the desired maximum
operating junction temperature, T J(MAX) . N1 and N2
have different loss components due to the circuit oper-
ation. N2 operates as a zero-voltage switch; therefore,
major losses are the channel-conduction loss (P N2CC )
and the body-diode conduction loss (P N2DC ).
? LIR ?
? 2 ?
Use R DS ( ON ) at T J ( MAX ) .
P N 2 DC = 2 × I LOAD × V F × t dt × f S
where V F is the body-diode forward-voltage drop, t dt is
the dead time between N1 and N2 switching transitions,
f S is the switching frequency, and t dt is 20ns (typ).
N1 operates as a duty-cycle control switch and has the
following major losses: the channel-conduction loss
(P N1CC ), the VL overlapping switching loss (P N1SW ),
and the drive loss (P N1DR ). N1 does not have body-
diode conduction loss, because the diode never con-
ducts current.
? V ?
? V IN ?
In addition to the losses above, allow approximately
20% for additional losses due to MOSFET output capac-
itances and N2 body-diode reverse-recovery charge
dissipated in N1 that exists, but is not well defined, in
the MOSFET data sheet. Refer to the MOSFET data
sheet for thermal-resistance specification to calculate
the PC board area needed to maintain the desired maxi-
mum operating junction temperature with the above cal-
culated power dissipations.
To reduce electromagnetic interference (EMI) caused
by switching noise, add a 0.1μF ceramic capacitor from
the high-side switch drain to the low-side switch source
or add resistors in series with DH and DL to slow down
the switching transitions. However, adding series resis-
tors increases the power dissipation of the MOSFET, so
be sure this does not overheat the MOSFET.
The minimum load current must exceed the high-side
MOSFET’s maximum leakage-current overtemperature
if fault conditions are expected.
MOSFET Snubber Circuit
Fast-switching transitions cause ringing because of
resonating circuit parasitic inductance and capaci-
tance at the switching nodes. This high-frequency ring-
ing occurs at LX’s rising and falling transitions and can
interfere with circuit performance and generate EMI. To
dampen this ringing, a series RC snubber circuit is
added across each switch. Below is the procedure for
selecting the value of the series RC circuit:
1) Connect a scope probe to measure the voltage
from LX to GND, and observe the ringing frequen-
cy, f R .
2) Find the capacitor value (connected from LX to
GND) that reduces the ringing frequency by half.
P N 1 SW = V IN × I LOAD × ?
?
? × f S
?
Use R DS ( ON ) at T J ( MAX ) .
? Q gs + Q gd
? I GATE
?
?
The circuit parasitic capacitance (C PAR ) at LX is then
equal to 1/3rd of the value of the added capacitance
above. The circuit parasitic inductance (L PAR ) is calculat-
ed by:
I GATE ? 0 . 5 ×
L PAR =
( 2 π f R )
× C PAR
where I GATE is the average DH-driver output current
capability determined by:
V IN
R DS ( ON )( N 2 ) + R GATE
where R DS(ON)(N2) is the high-side MOSFET driver’s
on-resistance (1.5 ? typ) and R GATE is the internal gate
resistance of the MOSFET (~2 ? ).
1
2
The resistor for critical dampening (R SNUB ) is equal to
2 π x f R x L PAR . Adjust the resistor value up or down to
tailor the desired damping and the peak voltage excur-
sion. The capacitor (C SNUB ) should be at least two to
four times the value of the C PAR to be effective. The
P RSNUB SNUB × ( V IN ) × f S
= C
P N 1 DR = Q g × V GS × f S ×
where V GS ~V IN.
R GATE
R GATE + R DS ( ON )( N 2 )
power loss of the snubber circuit (P RSNUB ) is dissipat-
ed in the resistor R SNUB and can be calculated as:
2
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1954AEUB-TG05 | 功能描述:电流型 PWM 控制器 RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MAX1954AEUB-TG077 | 功能描述:电流型 PWM 控制器 RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MAX1954AEVKIT | 功能描述:电流型 PWM 控制器 Evaluation Kit for the MAX1954A RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MAX1954BEUB | 功能描述:电流型 PWM 控制器 RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MAX1954BEUB+ | 功能描述:电流型 PWM 控制器 Current-Mode PWM Buck Controller RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
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