参数资料
型号: LTC4009IUF#PBF
厂商: LINEAR TECHNOLOGY CORP
元件分类: 稳压器
英文描述: BATTERY CHARGE CONTROLLER, 633 kHz SWITCHING FREQ-MAX, PQCC20
封装: 4 X 4 MM, 0.75 MM HEIGHT, LEAD FREE, PLASTIC, MO-220WGGD-1, QFN-20
文件页数: 16/28页
文件大小: 351K
代理商: LTC4009IUF#PBF
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LTC4009
LTC4009-1/LTC4009-2
The LTC4009 uses an improved adaptive TGATE and
BGATE drive that is insensitive to MOSFET inertial delays,
td(ON/OFF), to avoid overlap conduction losses. Switching
characteristics from power MOSFET data sheets apply
only to a specific test fixture, so there is no substitute for
bench evaluation of external FETs in the target application.
In general, MOSFETs with lower inertial delays will yield
higher efficiency.
Diode Selection
A Schottky diode in parallel with the bottom FET and/or
top FET in an LTC4009 application clamps SW during the
non-overlap times between conduction of the top and
bottom FET switches. This prevents the body diode of the
MOSFETs from forward biasing and storing charge, which
couldreduceefficiencyasmuchas1%.Oneorbothdiodes
can be omitted if the efficiency loss can be tolerated. A 1A
Schottky is generally a good size for 3A chargers due to the
low duty cycle of the non-overlap times. Larger diodes can
actually result in additional efficiency (transition) losses
due to larger junction capacitance.
Loop Compensation and Soft-Start
The three separate PWM control loops of the LTC4009
can be compensated by a single set of components at-
tached between the ITH pin and GND. As shown in the
typical LTC4009 application, a 6.04k resistor in series
with a capacitor of at least 0.1F provides adequate loop
compensation for the majority of applications.
The LTC4009 can be soft-started with the compensation
capacitor on the ITH pin. At start-up, ITH will quickly rise
to about 0.25V, then ramp up at a rate set by the com-
pensation capacitor and the 40A ITH bias current. The
full programmed charge current will be reached when ITH
reaches approximately 2V. With a 0.1F capacitor, the time
to reach full charge current is usually greater than 1.5ms.
This capacitor can be increased if longer start-up times
are required, but loop bandwidth and dynamic response
will be reduced.
INTVDD Regulator Output
Bypass the INTVDD regulator output to GND with a low
ESR X5R or X7R ceramic capacitor with a value of 0.47F
or larger. The capacitor used to build the BOOST supply
(C2 in Figure 11) can serve as this bypass. Do not draw
more than 30mA from this regulator for the host system,
governed by IC power dissipation.
Calculating IC Power Dissipation
The user should ensure that the maximum rated junction
temperatureisnotexceededunderalloperatingconditions.
The thermal resistance of the LTC4009 package (
θJA) is
37°C/W, provided the Exposed Pad is in good thermal
contact with the PCB. The actual thermal resistance in
the application will depend on forced air cooling and other
heat sinking means, especially the amount of copper on
the PCB to which the LTC4009 is attached. The following
formula may be used to estimate the maximum average
power dissipation PD (in watts) of the LTC4009, which is
dependent upon the gate charge of the external MOSFETs.
This gate charge, which is a function of both gate and drain
voltageswings,isdeterminedfromspecificationsorgraphs
in the manufacturer’s data sheet. For the equation below,
find the gate charge for each transistor assuming 5V gate
swing and a drain voltage swing equal to the maximum
VCLPvoltage.MaximumLTC4009powerdissipationunder
normal operating conditions is then given by:
PD = DCIN(2.8mA + IDD + 665kHz(QTGATE + QBGATE))
– 5IDD
where:
IDD = Average external INTVDD load current, if any
QTGATE = Gate charge of external top FET in Coulombs
QBGATE = Gate charge of external bottom FET in
Coulombs
applicaTions inForMaTion
相关PDF资料
PDF描述
LTC4009CUF-1#TRPBF BATTERY CHARGE CONTROLLER, 633 kHz SWITCHING FREQ-MAX, PQCC20
LTC4009CUF-2#TRPBF BATTERY CHARGE CONTROLLER, 633 kHz SWITCHING FREQ-MAX, PQCC20
LTC4009IUF-1#PBF BATTERY CHARGE CONTROLLER, 633 kHz SWITCHING FREQ-MAX, PQCC20
LTC4009CUF-2#PBF BATTERY CHARGE CONTROLLER, 633 kHz SWITCHING FREQ-MAX, PQCC20
LTC4009CUF-1#PBF BATTERY CHARGE CONTROLLER, 633 kHz SWITCHING FREQ-MAX, PQCC20
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