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参数资料
| 型号： | MAX1517ETJ |
| 厂商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分类： | 稳压器 |
| 英文描述： | TFT-LCD DC-DC Converters with Operational Amplifiers |
| 中文描述： | 1.6 A SWITCHING REGULATOR, 1380 kHz SWITCHING FREQ-MAX, PQCC32 |
| 封装： | 5 X 5 MM, 0.80 MM HEIGHT, MO-220-WHHD2, TQFN-32 |
| 文件页数： | 17/26页 |
| 文件大小： | 919K |
| 代理商： | MAX1517ETJ |
M
TFT-LCD DC-DC Converters with
Operational Amplifiers
______________________________________________________________________________________
17
Undervoltage Lockout (UVLO)
The undervoltage-lockout (UVLO) circuit compares the
input voltage at IN with the UVLO threshold (2.5V rising,
2.35V falling, typ) to ensure the input voltage is high
enough for reliable operation. The 150mV (typ) hysteresis
prevents supply transients from causing a restart. Once
the input voltage exceeds the UVLO rising threshold,
startup begins. When the input voltage falls below the
UVLO falling threshold, the controller turns off the main
step-up regulator, turns off the linear-regulator outputs,
and disables the switch control block; the operational-
amplifier outputs are high impedance.
Reference Voltage (REF)
The reference output is nominally 1.25V and can
source at least 50μA (see the
Typical Operating
Characteristics
). Bypass REF with a 0.22μF ceramic
capacitor connected between REF and AGND.
Power-Up Sequence and Soft-Start
Once the voltage on IN exceeds approximately 1.7V,
the reference turns on. With a 0.22μF REF bypass
capacitor, the reference reaches its regulation voltage
of 1.25V in approximately 1ms. When the reference
voltage exceeds 1.0V, the ICs enable the main step-up
regulator, the gate-on linear-regulator controller, and
the gate-off linear-regulator controller simultaneously.
The IC employs soft-start for each regulator to minimize
inrush current and voltage overshoot and to ensure a
well-defined startup behavior. During the soft-start, the
main step-up regulator directly limits the peak inductor
current. The current-limit level is increased through the
soft-start period from 0 up to the full current-limit value
in eight equal current steps (ILIM / 8). The maximum
load current is available after the output voltage reach-
es regulation (which terminates soft-start), or after the
soft-start timer expires. Both linear-regulator controllers
use a 7-bit soft-start DAC. For the gate-on linear regula-
tor, the DAC output is stepped in 128 steps from zero
up to the reference voltage. For the gate-off linear regu-
lator, the DAC output steps from the reference down to
250mV in 128 steps. The soft-start duration is 14ms
(typ) for all three regulators.
A capacitor (C
DEL
) from DEL to AGND determines the
switch-control-block startup delay. After the input volt-
age exceeds the UVLO threshold (2.5V typ) and the
soft-start routine for each regulator is complete and
there is no fault detected, a 5μA current source starts
charging C
DEL
. Once the capacitor voltage exceeds
1.25V (typ), the switch-control block is enabled as
shown in Figure 6. After the switch-control block is
enabled, COM can be connected to SRC or DRN
through the internal p-channel switches, depending
upon the state of CTL. Before startup and when IN is
less than V
UVLO
, DEL is internally connected to AGND
to discharge C
DEL
. Select C
DEL
to set the delay time
using the following equation:
Switch-Control Block
The switch-control input (CTL) is not activated until all
four of the following conditions are satisfied: the input
voltage exceeds V
UVLO
, the soft-start routine of all the
regulators is complete, there is no fault condition
detected, and V
DEL
exceeds its turn-on threshold. As
shown in Figure 7, COM is pulled down to PGND
through a 1k
resistor when the switch control is not
activated. Once activated and if CTL is high, the 5
internal p-channel switch (Q1) between COM and SRC
turns on and the 30
p-channel switch (Q2) between
DRN and COM turns off. If CTL is low, Q1 turns off and
Q2 turns on.
C
DELAY TIME
A
V
DEL
=
×
μ
_
.
5
1 25
12ms
2.5V
1.05V
1.25V
V
IN
V
REF
V
MAIN
V
GON
V
GOFF
V
DEL
SWITCH
CONTROL
ENABLED
SOFT-
START
ENDS
SOFT-
START
BEGINS
INPUT
VOLTAGE
OK
Figure 6. Power-Up Sequence
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1517ETJ+ | 功能描述:LCD 驱动器 TFT-LCD DC-DC Conv w/Op Amps RoHS:否 制造商:Maxim Integrated 数位数量:4.5 片段数量:30 最大时钟频率:19 KHz 工作电源电压:3 V to 3.6 V 最大工作温度:+ 85 C 最小工作温度:- 20 C 封装 / 箱体:PDIP-40 封装:Tube |
| MAX1517ETJ+G104 | 功能描述:LCD 驱动器 TFT-LCD DC-DC Converters with Operational Amplifiers RoHS:否 制造商:Maxim Integrated 数位数量:4.5 片段数量:30 最大时钟频率:19 KHz 工作电源电压:3 V to 3.6 V 最大工作温度:+ 85 C 最小工作温度:- 20 C 封装 / 箱体:PDIP-40 封装:Tube |
| MAX1517ETJ+T | 功能描述:LCD 驱动器 TFT-LCD DC-DC Conv w/Op Amps RoHS:否 制造商:Maxim Integrated 数位数量:4.5 片段数量:30 最大时钟频率:19 KHz 工作电源电压:3 V to 3.6 V 最大工作温度:+ 85 C 最小工作温度:- 20 C 封装 / 箱体:PDIP-40 封装:Tube |
| MAX1517ETJ+TG104 | 功能描述:LCD 驱动器 TFT-LCD DC-DC Converters with Operational Amplifiers RoHS:否 制造商:Maxim Integrated 数位数量:4.5 片段数量:30 最大时钟频率:19 KHz 工作电源电压:3 V to 3.6 V 最大工作温度:+ 85 C 最小工作温度:- 20 C 封装 / 箱体:PDIP-40 封装:Tube |
| MAX1517ETJ-T | 功能描述:LCD 驱动器 RoHS:否 制造商:Maxim Integrated 数位数量:4.5 片段数量:30 最大时钟频率:19 KHz 工作电源电压:3 V to 3.6 V 最大工作温度:+ 85 C 最小工作温度:- 20 C 封装 / 箱体:PDIP-40 封装:Tube |
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