参数资料
| 型号： | MIC22602YML TR |
| 厂商： | Micrel Inc |
| 文件页数： | 13/24页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC ADJ 6A 24MLF |
| 标准包装： | 1 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 可调至 0.7V |
| 输入电压： | 2.6 V ~ 5.5 V |
| PWM 型： | 电压模式 |
| 频率 - 开关： | 1MHz |
| 电流 - 输出： | 6A |
| 同步整流器： | 是 |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 24-VFQFN 裸露焊盘，24-MLF? |
| 包装： | 标准包装 |
| 供应商设备封装： | 24-MLF?（4x4） |
| 其它名称： | 576-3645-6 |
R 2 =
? ?
? 1 ? ?
delays are matched at T POR =
Micrel, Inc.
Feedback
The MIC22602 provides a feedback pin to adjust the
output voltage to the desired level. This pin connects
internally to an error amplifier. The error amplifier then
compares the voltage at the feedback to the internal
0.7V reference voltage and adjusts the output voltage to
maintain regulation. The resistor divider network for a
desired V OUT is given by:
R 1
? V OUT ?
? V REF ?
where V REF is 0.7V and V OUT is the desired output
voltage. A 10k ? or lower resistor value from the output
to the feedback is recommended since large feedback
resistor values increase the impedance at the feedback
pin, making the feedback node more susceptible to
noise pick-up. A small capacitor (50pF – 100pF) across
the lower resistor can reduce noise pick-up by providing
a low impedance path to ground.
PWM Operation
The MIC22602 is a voltage mode, pulse width
modulation (PWM) controller. By controlling the duty
cycle, a regulated DC output voltage is achieved. As
load or supply voltage changes, so does the duty cycle
to maintain a constant output voltage. In cases where
the input supply runs into a dropout condition, the
MIC22602 will run at 100% duty cycle.
The MIC22602 provides constant switching at 1MHz with
synchronous internal MOSFETs. The internal MOSFETs
include a high-side P-Channel MOSFET from the input
supply to the switch pin and an N-Channel MOSFET
from the switch pin-to-ground. Since the low-side N-
Channel MOSFET provides the current during the off
cycle, very low power is dissipated during the off period.
PWM control provides fixed frequency operation. By
maintaining a constant switching frequency, predictable
fundamental and harmonic frequencies are achieved.
Sequencing and tracking
The MIC22602 provides additional pins to provide
up/down sequencing and tracking capability for
connecting multiple voltage regulators together.
MIC22602
EN/DLY pin
The EN pin contains a trimmed, 1μA current source
which can be used with a capacitor to implement a fixed
desired delay in some sequenced power systems. The
threshold level for power on is 1.24V with a hysteresis of
20mV.
DELAY Pin
The DELAY pin also has a 1μA trimmed current source
and a 1μA current sink which acts with an external
capacitor to delay the operation of the Power On Reset
(POR) output. This can be used also in sequencing
outputs in a sequenced system, but with the addition of a
conditional delay between supplies; allowing a first up,
last down power sequence.
After EN is driven high, V OUT will start to rise (rate
determined by RC capacitor). As the FB voltage goes
above 90% of its nominal set voltage, DELAY begins to
rise as the 1μA source charges the external capacitor.
When the threshold of 1.24V is crossed, POR is
asserted high and DELAY continues to charge to a
voltage SVIN. When FB falls below 90% of nominal,
POR is asserted low immediately. However, if EN is
driven low, POR will fall immediately to the low state and
DELAY will begin to fall as the external capacitor is
discharged by the 1μA current sink. When the threshold
of (V TP +1.24V)-1.24V is crossed (V TP is the internal
voltage clamp V TP ≈ 0.9V ), V OUT will begin to fall at a
rate determined by the RC capacitor. As the voltage
change in both cases is 1.24V, both rising and falling
1 . 24 ? C DLY
1 × 10 ? 6
RC pin
The RC pin provides a trimmed 1μA current source/sink
similar to the DELAY Pin for accurate ramp up (soft
start) and ramp down control. This allows the MIC22602
to be used in systems requiring voltage tracking or ratio-
metric voltage tracking at startup.
There are two ways of using the RC pin:
1. Externally driven from a voltage source
2. Externally attached capacitor sets output ramp
up/down rate
In the first case, driving RC with a voltage from 0V to
V REF programs the output voltage between 0 and 100%
of the nominal set voltage.
In the second case, the external capacitor sets the ramp
up and ramp down time of the output voltage. The time
is given by T RAMP =
0 . 7 ? C RC
1 × 10 ? 6
where T RAMP is the time
from 0 to 100% nominal output voltage.
The RC pin cannot be left floating. Use a minimum
capacitor value of 470pF or larger.
October 2009
13
M9999-102809-A
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