参数资料
型号: MAX8513EVKIT
厂商: Maxim Integrated Products
文件页数: 29/35页
文件大小: 0K
描述: EVAL KIT FOR MAX8513
产品培训模块: Lead (SnPb) Finish for COTS
Obsolescence Mitigation Program
标准包装: 1
主要目的: DC/DC,LDO 步降
输出及类型: 3,非隔离
输出电压: 3.3V,2.5V,12V
电流 - 输出: 2A,1.5A,100mA
输入电压: 9 ~ 16 V
稳压器拓扑结构: 降压
频率 - 开关: 1.4MHz
板类型: 完全填充
已供物品:
已用 IC / 零件: MAX8513
Wide-Input, High-Frequency, Triple-Output Supplies
with Voltage Monitor and Power-On Reset
the package’s power dissipation could limit the useable
maximum input-to-output voltage differential.
The maximum power-dissipation capability of the tran-
sistor’s package and mounting must allow the actual
power dissipation in the device without exceeding the
maximum junction temperature. The power dissipated
equals the maximum load current multiplied by the
maximum input-to-output voltage differential.
When the MAX8513/MAX8514 are disabled, R26 dis-
charges C7.
OUT3P Voltage Selection (PNP)
The MAX8513 positive linear-regulator output voltage,
V OUT3P , is set with a resistive-divider from OUT3P to
FB3P to GND. First, select R14 resistance value (below
1k ? ). Then, solve for R13 so:
transistor’s specifications, the base-emitter resistor,
and the output capacitor determine the loop stability.
The total DC loop gain (A V ) is the product of the gains
of the internal transconductance amplifier, the gain
from base to collector of the pass transistor (Q4 in the
Typical Applications Circuits ), and the gain of the feed-
back divider.
The transconductance amplifier regulates the output
voltage by controlling the pass transistor’s base cur-
rent. Its DC gain is approximately:
G C 3 _ × R IN || R 12
where G C3_ is typically 0.6S (OUT3P) and 0.36S
(OUT3N), R IN is the input resistance of Q4, and can be
calculated by:
R 13 = R 14 ? OUT 3 P -1 ?
R IN = ?
? V ?
? 0 . 8 V ?
? 26 mV
? I OUT 3 _
?
β ?
?
where V OUT3P can range from +0.8V to +27V.
OUT3N Voltage Selection (NPN)
The DC gain for the transistor (Q4), including the feed-
back divider, is approximately:
The MAX8514’s negative linear-regulator output volt-
age, V OUT3N , is a negative regulated voltage devel-
oped through the pass transistor Q4 (MAX8514 Typical
A Q 4 P =
V REF
VT
for OUT 3 P or
Applications Circuits ). A resistive-divider from OUT3N
to FB3N to V REF3N forces V FB3N to regulate to 0V.
Calculate V OUT3N by first selecting R14 the resistor
A Q 4 N =
V OUT 3 N × V REF 3 N
( V REF 3 N - V OUT 3 N ) × V T
from V REF3N to FB3N to be below 5k ? , where V REF3N
is any positive voltage (usually V OUT1 ). R13 is then cal-
culated by:
V T is the thermal voltage for the transistor (typically 26mV
at T A = +27 ° C). The total DC loop gain for OUT3_ is:
( )
R 13 =
-V OUT 3N
V REF 3 N
× R 14
A V = G C 3 _ × R IN || R 12 × A Q 4 _
SUP3N is the supply input for OUT3N’s transconduc-
tance amplifier. When OUT3N is used, SUP3N must be
A dominant pole (f POLE1 ) is created from the output
capacitance and load resistance:
connected to a voltage supply between 1.5V and 5.5V
that can source at least 25mA. Typically, V OUT1 can be
used as the supply input for SUP3N.
f POLE 1 =
1
2 π × C OUT 3 × R OUT 3
=
I OUT 3 _ MAX
2 π × C OUT 3 × V OUT 3 _
Stability Requirements
The MAX8513/MAX8514s’ DRV3P and DRV3N outputs
are designed to drive bipolar transistors (PNP types for
the MAX8513 with the DRV3P output, and NPN types
for the MAX8514 with the DRV3N output). These bipolar
transistors form linear regulators with positive outputs
(MAX8513 from 0.8V to 27V) and negative outputs
(MAX8514 from -18V to -1V). An internal transconduc-
tance amplifier is used to drive the external pass tran-
sistors. The transconductance amplifier, pass
Unity-gain crossover (f C_OUT3_ ) should occur at:
f C _ OUT 3 _ = A V × f POLE 1
A second pole is set by the input capacitance to the
base of Q4 (C Q4IN ), any external base-to-emitter
capacitance (C BE , see the Base-Drive Noise Reduction
section and Figure 7), the transistor’s input resistance
(R IN ), and the base-to-emitter pullup resistor (R12):
______________________________________________________________________________________
29
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