參數(shù)資料
型號: MAX1964TEEE
廠商: MAXIM INTEGRATED PRODUCTS INC
元件分類: 穩(wěn)壓器
英文描述: Tracking/Sequencing Triple/Quintuple Power-Supply Controllers
中文描述: 0.05 A SWITCHING CONTROLLER, 240 kHz SWITCHING FREQ-MAX, PDSO16
封裝: 0.150 INCH, 0.025 INCH PITCH, QSOP-16
文件頁數(shù): 24/30頁
文件大?。?/td> 475K
代理商: MAX1964TEEE
M
where C
IN(Q)
is the transistor
s input capacitance, and
f
POLE(CBE)
is the second pole required for stability.
Transformer Selection
In systems where the step-down controller
s output is
not the highest voltage, a transformer may be used to
provide additional post-regulated, high-voltage outputs.
The transformer generates unregulated, high-voltage
supplies which power the positive and negative linear
regulators. These unregulated supply voltages are
dependent on the transformer
s turns ratio
number of
secondary turns (N
S
) divided by the number of primary
turns (N
P
). So the transformer must be selected to pro-
vide supply voltages high enough to keep the pass
transistors from saturating. For positive output voltages,
connect the transformer as shown in Figure 6 where the
minimum turns ratio (N
POS
= N
S(POS)
/N
P
) is determined
by:
where V
SAT
is the pass transistor
s saturation voltage
under full load. For negative output voltages (MAX1965
only), connect the transformer as shown in Figure 6
where the minimum turns ratio (N
NEG
= N
S(NEG)
/N
P
) is
determined by:
Since power transfer occurs when the low-side MOS-
FET is on (DL = high), the transformer cannot support
heavy loads with high duty cycles.
Snubber Design
The MAX1964/MAX1965 use current-mode control
schemes that sense the current across the high-side
MOSFET (N
H
). Immediately after the high-side MOSFET
turns on, the MAX1964/MAX1965 use a 60ns current-
sense blanking period to minimize noise sensitivity.
However, when the MOSFET turns on, the transformer
s
secondary inductance and the diode
s parasitic capac-
itance form a resonant circuit that causes ringing.
Reflected back through the transformer to the primary
side, these oscillations appear across the high-side
MOSFET may last longer than the blanking period. As
N
V
V
V
V
NEG
LDO NEG
(
SAT
DIODE
OUT
+
+
)
N
V
V
V
V
POS
LDO POS
(
SAT
DIODE
OUT
+
+
)
-1
C
R
R
V h
C
BE
POLE CBE
BELOAD
BE T FE
I( )
+
1
2
π
(
)
-
Tracking/Sequencing Triple/Quintuple
Power-Supply Controllers
24
______________________________________________________________________________________
Figure 7. Base-Drive Noise Reduction
C
BYP
V
NEG
V
SUP
Q
PASS
C
LDO
R
BE
C
BE
R1
R2
B_
a) POSITIVE OUTPUT VOLTAGE
b) NEGATIVE OUTPUT VOLTAGE (MAX1965 ONLY)
FB_
MAX1964
MAX1965
V
POS
C
BYP
V
REF
V
SUP
Q
PASS
C
NEG
R
BE
C
BE
R4
R3
BF5
B5
MAX1965
相關PDF資料
PDF描述
MAX1965TEEP Tracking/Sequencing Triple/Quintuple Power-Supply Controllers
MAX1966 Low-Cost Voltage-Mode PWM Step-Down Controllers
MAX1967EUB Low-Cost Voltage-Mode PWM Step-Down Controllers
MAX1966-MAX1967 Low-Cost Voltage-Mode PWM Step-Down Controllers
MAX1966ESA Low-Cost Voltage-Mode PWM Step-Down Controllers
相關代理商/技術參數(shù)
參數(shù)描述
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