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參數(shù)資料
| 型號： | MAX1964 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | Tracking/Sequencing Triple/Quintuple Power-Supply Controllers |
| 中文描述： | 三/五路電源控制器，提供跟蹤/排序功能 |
| 文件頁數(shù)： | 16/30頁 |
| 文件大小： | 475K |
| 代理商： | MAX1964 |
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M
during startup. The soft-start period is 1024 clock
cycles (1024/f
OSC
), and the internal soft-start DAC
ramps up the voltage in 64 steps. The output reaches
regulation when soft-start is completed, regardless of
output capacitance and load.
Output Voltage Sequencing (MAX1964)
After the reference powers up, the controller begins a
startup sequence. First, the main DC-DC step-down
converter powers up with soft-start enabled. Once the
step-down converter reaches 92% of its nominal value
(V
FB
> 1.145V) and soft-start is completed, the con-
troller powers up the first positive linear regulator. Once
the first linear regulator reaches 92% of its nominal
value (V
FB2
> 1.145V), the second linear regulator pow-
ers up. Once all three output voltages exceed 92% of
their nominal values, the active-high ready signal (POK)
goes high (see
Power-Good Output
section).
Output Voltage Tracking (MAX1965)
After the reference powers up, the controller simultane-
ously powers up all five output voltages. The main DC-
DC step-down converter powers up with soft-start
enabled while the linear regulators are fully activated.
However, the linear regulators
’
inputs are typically con-
nected to or derived from the step-down converter out-
put voltage. Since the linear regulators are fully active,
the pass transistors immediately saturate, allowing
these output voltages to track the step-down convert-
er
’
s slow rising output voltage (see
Typical Operating
Characteristics
). Once all five output voltages exceed
92% of their nominal values, the active-high ready sig-
nal (POK) goes high (see
Power-Good Output
section).
Power-Good Output (POK)
POK is an open-drain output. The MOSFET turns on
and pulls POK low when any output falls below 90% of
its nominal regulation voltage. Once all of the outputs
exceed 92% of their nominal regulation voltages and
soft-start is completed, POK goes high impedance. To
obtain a logic voltage output, connect a pullup resistor
from POK to VL. A 100k
resistor works well for most
applications. If unused, leave POK grounded or uncon-
nected.
Thermal overload Protection
Thermal overload protection limits total power dissipa-
tion in the MAX1964/MAX1965. When the junction tem-
perature exceeds T
J
= +160
°
C, a thermal sensor shuts
down the device, forcing DL and DH low, allowing the
IC to cool. The thermal sensor turns the part on again
after the junction temperature cools by 15
°
C, resulting
in a pulsed output during continuous thermal overload
conditions. If the VL output is short-circuited, thermal
overload protection is disabled.
During a thermal event, the main step-down converter
and the linear regulators are turned off, POK goes low,
and soft-start is reset.
Design Procedure
DC-DC Step-Down Converter
Output Voltage Selection
The step-down controller
’
s feedback input features dual
mode operation. Connect the output to OUT and con-
nect FB to GND for the preset 3.3V output voltage.
Alternatively, the MAX1964/MAX1965 output voltage
may be adjusted by connecting a voltage-divider from
the output to FB to GND (Figure 4). Select R2 in the
5k
to 50k
range. Calculate R1 with the following
equation:
where V
SET
= 1.236V and V
OUT
may range from 1.236V
to approximately 0.75
V
IN
(up to 20V). If V
OUT
> 5.5V,
connect OUT to GND (MAX1964) or to one of the posi-
tive linear regulators (MAX1965) with an output voltage
between 2V and 5V.
Inductor Value
Three key inductor parameters must be specified:
inductance value (L), peak current (I
PEAK
), and DC
resistance (R
DC
). The following equation includes a
constant LIR, which is the ratio of inductor peak-to-peak
AC current to DC load current. A higher LIR value
allows smaller inductance, but results in higher losses
and higher output ripple. A good compromise between
size and losses is a 30% ripple-current to load-current
ratio (LIR = 0.3). The switching frequency, input volt-
age, output voltage, selected LIR determine the induc-
tor value as follows:
where f
SW
is 200kHz. The exact inductor value is not
critical and can be adjusted in order to make trade-offs
among size, cost, and efficiency. Lower inductor values
minimize size and cost, but they also increase the out-
put ripple and reduce the efficiency due to higher peak
currents. On the other hand, higher inductor values
increase efficiency, but at some point resistive losses
due to extra turns of wire will exceed the benefit gained
from lower AC current levels.
L
V
V
V
V
LIR
)
OUT
IN
OUT
IN SW LOAD MAX
=
(
)
-
(
R
R
V
V
OUT
SET
1
2
1
=
-
Tracking/Sequencing Triple/Quintuple
Power-Supply Controllers
16
______________________________________________________________________________________
相關PDF資料 |
PDF描述 |
|---|---|
| MAX1965 | Tracking/Sequencing Triple/Quintuple Power-Supply Controllers |
| MAX1964TEEE | Tracking/Sequencing Triple/Quintuple Power-Supply Controllers |
| MAX1965TEEP | Tracking/Sequencing Triple/Quintuple Power-Supply Controllers |
| MAX1966 | Low-Cost Voltage-Mode PWM Step-Down Controllers |
| MAX1967EUB | Low-Cost Voltage-Mode PWM Step-Down Controllers |
相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| MAX1964TEEE | 功能描述:電流和電力監(jiān)控器、調(diào)節(jié)器 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Current Regulators 電源電壓-最大:48 V 電源電壓-最小:5.5 V 工作溫度范圍:- 40 C to + 150 C 安裝風格:SMD/SMT 封裝 / 箱體:HPSO-8 封裝:Reel |
| MAX1964TEEE+ | 功能描述:電流和電力監(jiān)控器、調(diào)節(jié)器 Track/Seq Trpl/Wuint Power-Supply Ctlr RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Current Regulators 電源電壓-最大:48 V 電源電壓-最小:5.5 V 工作溫度范圍:- 40 C to + 150 C 安裝風格:SMD/SMT 封裝 / 箱體:HPSO-8 封裝:Reel |
| MAX1964TEEE+T | 功能描述:電流和電力監(jiān)控器、調(diào)節(jié)器 Track/Seq Trpl/Wuint Power-Supply Ctlr RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Current Regulators 電源電壓-最大:48 V 電源電壓-最小:5.5 V 工作溫度范圍:- 40 C to + 150 C 安裝風格:SMD/SMT 封裝 / 箱體:HPSO-8 封裝:Reel |
| MAX1964TEEE-T | 功能描述:電流和電力監(jiān)控器、調(diào)節(jié)器 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Current Regulators 電源電壓-最大:48 V 電源電壓-最小:5.5 V 工作溫度范圍:- 40 C to + 150 C 安裝風格:SMD/SMT 封裝 / 箱體:HPSO-8 封裝:Reel |
| MAX1965TEEP | 功能描述:電流和電力監(jiān)控器、調(diào)節(jié)器 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Current Regulators 電源電壓-最大:48 V 電源電壓-最小:5.5 V 工作溫度范圍:- 40 C to + 150 C 安裝風格:SMD/SMT 封裝 / 箱體:HPSO-8 封裝:Reel |
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