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| 型号： | MAX15053AEWL+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 12/21页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC ADJ 2A 9WLP |
| 标准包装： | 2,500 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 0.6 V ~ 5.17 V |
| 输入电压： | 2.7 V ~ 5.5 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 1MHz |
| 电流 - 输出： | 2A |
| 同步整流器： | 是 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | * |
| 封装/外壳： | * |
| 包装： | * |
| 供应商设备封装： | * |
High-Efficiency, 2A, Current-Mode
Synchronous, Step-Down Switching Regulator
R1 = R2 × ? OUT ? 1 ?
× ? 1 ? OUT ?
L =
Error Amplifier
A high-gain error amplifier provides accuracy for the
voltage-feedback loop regulation. Connect the neces-
sary compensation network between COMP and GND
(see the Compensation Design Guidelines section). The
error-amplifier transconductance is 1.5mS (typ). COMP
clamp low is set to 0.94V (typ), just below the slope ramp
compensation valley, helping COMP to rapidly return to
the correct set point during load and line transients.
PWM Comparator
The PWM comparator compares COMP voltage to the
current-derived ramp waveform (LX current to COMP
voltage transconductance value is 18A/V typ). To avoid
instability due to subharmonic oscillations when the duty
cycle is around 50% or higher, a slope compensation
ramp is added to the current-derived ramp waveform.
The compensation ramp slope (0.3V x 1MHz = 0.3V/ F s)
is equivalent to half the inductor current downslope in the
worst case (load 2A, current ripple 30% and maximum
duty-cycle operation of 94%). The slope compensation
ramp valley is set to 1.15V (typ).
Overcurrent Protection and Hiccup
When the converter output is shorted or the device is
overloaded, each high-side MOSFET current-limit event
(4A typ) turns off the high-side MOSFET and turns on the
low-side MOSFET. On each current-limit event a 3-bit
counter is incremented. The counter is reset after three
consecutive high-side MOSFETs turn on without reach-
ing current limit. If the current-limit condition persists,
the counter fills up reaching eight events. The control
logic then discharges SS/REFIN, stops both high-side
and low-side MOSFETs, and waits for a hiccup period
(1024 clock cycles typ) before attempting a new soft-
start sequence. The hiccup mode is also enabled during
soft-start time.
Thermal-Shutdown Protection
The MAX15053 contains an internal thermal sensor that
limits the total power dissipation to protect the device in
the event of an extended thermal fault condition. When
the die temperature exceeds +150 N C (typ), the thermal
sensor shuts down the device, turning off the DC-DC
converter to allow the die to cool. After the die tempera-
ture falls by 20 N C (typ), the device restarts, following the
soft-start sequence.
Skip Mode Operation
The MAX15053 operates in skip mode when SKIP is con-
nected to EN. When in skip mode, LX output becomes
high impedance when the inductor current falls below
200mA (typ). The inductor current does not become
negative. If during a clock cycle the inductor current falls
below the 200mA threshold (during off-time), the low side
turns off. At the next clock cycle, if the output voltage is
above set point, the PWM logic keeps both high-side
and low-side MOSFETs off. If instead the output voltage
is below the set point, the PWM logic drives the high-
side on for a minimum fixed on-time (300ns typ). In this
way the system can skip cycles, reducing frequency of
operations, and switches only as needed to service load
at the cost of an increase in output voltage ripple (see
the Skip Mode Frequency and Output Ripple section). In
skip mode, power dissipation is reduced and efficiency
is improved at light loads because power MOSFETs do
not switch at every clock cycle.
Applications Information
Setting the Output Voltage
The MAX15053 output voltage is adjustable from 0.6V
up to 94% of V IN by connecting FB to the center tap of a
resistor-divider between the output and GND (Figure 1).
Choose R1 and R2 so that the DC errors due to the FB
input bias current ( Q 500nA) do not affect the output volt-
age accuracy. With lower value resistors, the DC error
is reduced, but the amount of power consumed in the
resistor-divider increases. A typical value for R2 is 10k I ,
but values between 5k I and 50k I are acceptable. Once
R2 is chosen, calculate R1 using:
? V ?
? V FB ?
where the feedback threshold voltage, V FB = 0.6V (typ).
When regulating for an output of 0.6V in skip mode, short
FB to OUT and keep R2 connected from FB to GND.
Inductor Selection
A high-valued inductor results in reduced inductor ripple
current, leading to a reduced output ripple voltage.
However, a high-valued inductor results in either a larger
physical size or a high series resistance (DCR) and a
lower saturation current rating. Typically, choose an
inductor value to produce a current ripple equal to 30%
of load current. Choose the inductor with the following
formula:
V OUT ? V ?
f SW × LIR × I LOAD ? V IN ?
where f SW is the internally fixed 1MHz switching frequen-
cy, and LIR is the desired inductor current ratio (typically
12
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