參數(shù)資料
型號(hào)： MAX783EBX
廠商： MAXIM INTEGRATED PRODUCTS INC
元件分類： 穩(wěn)壓器
英文描述： Hex Inverters 14-CDIP -55 to 125
中文描述： DUAL SWITCHING CONTROLLER, 330 kHz SWITCHING FREQ-MAX, PDSO36
封裝： PLASTIC, SSOP-36
文件頁(yè)數(shù)： 13/28頁(yè)
文件大小： 279K
代理商： MAX783EBX
M
Triple-Output Power-S upply Controller
for Notebook Computers
______________________________________________________________________________________
13
continuously receiving current from the inductor. This
minimizes output ripple and maximizes inductor use,
allowing very small physical and electrical sizes. Output
ripple is primarily a function of the filter capacitor effec-
tive series resistance (ESR) and is typically under 50mV
(see the Design Procedure section). Output ripple is
worst at light load and maximum input voltage.
Idle Mode
Under light loads (<25% of full load), efficiency is fur-
ther enhanced by turning the drive voltage on and off
for only a single clock period, skipping most of the
clock pulses entirely. Asynchronous switching, seen as
“ghosting” on an oscilloscope, is thus a normal operating
condition whenever the load current is less than
approximately 25% of full load.
At certain input voltage and load conditions, a transition
region exists where the controller can pass back and
forth from idle-mode to PWM mode. In this situation,
short bursts of pulses occur that make the current
waveform look erratic, but do not materially affect the
output ripple. Efficiency remains high.
Current Limiting
The voltage between CS3 (CS5) and FB3 (FB5) is contin-
uously monitored. An external, low-value shunt resistor
is connected between these pins, in series with the
inductor, allowing the inductor current to be continuously
measured throughout the switching cycle. Whenever
this voltage exceeds 100mV, the drive voltage to the
external high-side MOSFET is cut off. This protects the
MOSFET, the load, and the battery in case of short cir-
cuits or temporary load surges. The current-limiting
resistor R1 (R2) is typically 25m
(20m
) for a 3A load
current.
Oscillator Frequency; SYNC Input
The SYNC input controls the oscillator frequency.
Connecting SYNC to GND or to VL selects 200kHz opera-
tion; connecting to REF selects 300kHz operation. SYNC
can also be driven with an external 240kHz to 350kHz
CMOS/TTL source to synchronize the internal oscillator.
300kHz operation is used to minimize the inductor and
filter capacitor sizes, but 200kHz may be necessary for
low input voltages (see Low-Voltage Operation.
High-S ide S upply (V DD)
The 15V VDD supply is obtained from the rectified and
filtered secondary of transformer L2. VDD is enabled
whenever the +3.3V supply is on (ON3 = high). The
primary and secondary of L2 are connected so that,
during the flyback (discharge) portion of each cycle,
energy stored in the core is transferred into the +3.3V
load through the primary and into VDD through the sec-
ondary, as determined by the turns ratio. The sec-
ondary voltage is added to the +3.3V to make VDD.
See the Typical Operating Characteristics for the VDD
supply’s load capability.
Unlike other coupled-inductor flyback converters, the
VDD voltage is regulated regardless of the loading on
the +3.3V output. (Most coupled-inductor converters
can only support the auxiliary output when the main
output is loaded.) When the +3.3V supply is lightly
loaded, the circuit achieves good control of VDD by
pulsing the MOSFET normally used as the synchronous
rectifier. This draws energy from the +3.3V supply’s
output capacitor and uses the transformer in a forward-
converter mode (i.e., the +15V output takes energy out
of the secondary when current is flowing in the prima-
ry). These forward-converter pulses are interspersed
with normal synchronous-rectifier pulses, and they only
occur at light loads on the +3.3V rail.
The transformer secondary’s rectified and filtered out-
put is only roughly regulated, and may be between 13V
and 19V. It is brought back into VDD, which is also the
feedback input, and used as the source for the PCMCIA
VPP regulators. It can also be used as the VH power
supply for the comparators or any external MOSFET
drivers.
When the input voltage is above 12V, or when the
+3.3V supply is heavily loaded and VDD is lightly
loaded, L2’s interwinding capacitance and leakage
inductance can produce voltages above that calculat-
ed from the turns ratio. A 2.5mA shunt regulator limits
VDD to 19V. If the battery voltage can rise above 12V,
VDD must either be externally clamped with an 18V
zener diode, or there must be a 1mA minimum load on
VDD (or VPPA/VPPB).
Clock-frequency noise on the VDD rail of up to 3V
P-P
is
a facet of normal operation, and can be reduced by
adding more output capacitance.
PCMCIA-Compatible,
Programmable V PP S upplies
Two independent linear regulators furnish PCMCIA VPP
supplies. The VPPA and VPPB outputs can be pro-
grammed to deliver 0V, 3.3V, 5V, or 12V. The 0V out-
put mode has a 250
pull-down to discharge external
filter capacitors and ensure that flash EPROMs cannot
be accidentally programmed. These linear regulators
draw their power from the high-side supply (VDD), and
each can furnish up to 60mA. Bypass VPPA and VPPB
to GND with at least 1μF, with the bypass capacitors
less than 20mm from the VPP pins.
The outputs are programmed with DA0, DA1, DB0 and
DB1, as shown in Table 2.
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
MAX783EBX+ 功能描述:DC/DC 開關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK
MAX783EBX+T 功能描述:DC/DC 開關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK
MAX783EBX-T 功能描述:DC/DC 開關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK
MAX783EVKIT-SO 功能描述:DC/DC 開關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK
MAX783SCBX 功能描述:DC/DC 開關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK
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