参数资料
型号: MAX1515ETG+
厂商: Maxim Integrated Products
文件页数: 17/24页
文件大小: 0K
描述: IC REG DDR LV 24-TQFN
产品培训模块: Lead (SnPb) Finish for COTS
Obsolescence Mitigation Program
标准包装: 75
应用: 转换器,DDR
输入电压: 1.3 V ~ 3.6 V
输出数: 2
输出电压: 0.5 V ~ 2.7 V
工作温度: -40°C ~ 85°C
安装类型: 表面贴装
封装/外壳: 24-WFQFN 裸露焊盘
供应商设备封装: 24-TQFN-EP(4x4)
包装: 管件
Low-Voltage, Internal Switch,
Step-Down/DDR Regulator
= V
+ R ?
V FB REF ?
resistive divider between REF and ground (Figure 5).
Regulation is maintained for adjustable output voltages
when V FB = V REFIN . Use 100k Ω for R B . R A is given by
the equation:
? R B ?
? R A B ?
where V REF = 1.1V.
LOAD
CURRENT
INDUCTOR
CURRENT
OUTPUT
0
-2A
0
-2A
V REFIN
The preset output voltages use an internally trimmed
resistor-divider network that sets the output voltage to
VOLTAGE
V IN
the correct level when REFIN is connected to REF.
Connecting REFIN to other voltage levels while using
the preset voltage modes results in a ratiometrically
scaled output voltage.
Output Voltage in DDR Mode
LX
VOLTAGE
t OFF
Figure 4. Sink-Mode Waveforms
V OUT
GND
In DDR mode (MODE = V CC ), the MAX1515 regulates
FB to the voltage set at REFIN. For DDR applications,
the termination supply must track to exactly half the
REF
LX
L
V OUT
memory supply voltage. Figure 1 shows the MAX1515
configured for DDR applications.
Reference Buffer (REFOUT)
A unity-gain amplifier provides a buffered output for the
reference input (V REFIN ) when MODE = V CC . This
R A
R B
REFIN
MAX1515
PGND
GND
FB
C OUT
transconductance amplifier must be compensated with
a 0.47μF or greater ceramic capacitor. Larger capaci-
tor values decrease the amplifier’s bandwidth, thereby
increasing the response time to dynamic input-voltage
changes. The buffer allows this dynamic reference to
remain within ±20mV of the input voltage (V REFIN ) even
when loaded with ±5mA. The input voltage range of the
amplifier is 0.5V to 1.5V. The reference buffer shuts
down when MODE = GND.
Power-Good Output (PGOOD)
PGOOD is the open-drain output for a window compara-
tor that continuously monitors the output. PGOOD is
actively held low in shutdown and during soft-start. After
soft-start terminates, PGOOD becomes high impedance
as long as the respective output voltage is within ±10%
of the nominal regulation voltage. When the output volt-
age drops 10% below or rises 10% above the nominal
regulation voltage, the MAX1515 pulls the power-good
output (PGOOD) low by turning on the MOSFET (Figure
2). For logic-level output voltages, connect an external
pullup resistor between PGOOD and V CC . A 100k Ω
resistor works well in most applications.
Thermal Shutdown
The MAX1515 features a thermal fault-protection circuit.
When the junction temperature rises above +165 ° C, a
thermal sensor shuts down the MAX1515 regardless of
MODE
FBSEL0
FBSEL1
Figure 5. Setting VOUT with a Resistive Voltage-Divider at REFIN
V SHDN . The MAX1515 is reactivated after the junction
temperature cools to +150 ° C.
Thermal Resistance
Junction-to-ambient thermal resistance, θ JA , is highly
dependent on the amount of copper area connected to
the exposed backside pad. Airflow over the board sig-
nificantly reduces θ JA . For heatsinking purposes, evenly
distribute the copper area connected at the IC among
the high-current pins. Refer to the Maxim website
(www.maxim-ic.com) for QFN thermal considerations.
Power Dissipation
Power dissipation in the MAX1515 is dominated by
conduction losses in the two internal power switches.
Power dissipation due to supply current in the control
section and average current used to charge and dis-
charge the gate capacitance of the internal switches
(i.e., switching losses—PSL) is approximately:
PSL = C x V IN 2 x f SW
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17
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