Datasheet

10:
LM5015
VIN
PVIN
AGND
PGND
(a) Analog Input Powered from the Main Power
LM5015
VIN
PVIN
AGND
PGND
(b) Analog Input Powered from a Separate Bias Source
V
PWR
0.1
PF
V
PWR
as
V
Bi
0.1
PF
LM5015
SNVS538C –NOVEMBER 2007–REVISED APRIL 2013 www.ti.com
Figure 14. Analog and Power Input Ports
The PVIN and PGND pins are internally connected to the high and low side power MOSFETs, respectively.
When designing the PC board, the input filter capacitor should connect directly to these pins with short
connection traces.
The VIN operating range is 4.25V to 75V. The current drawn into the VIN pin depends primarily on the gate
charge of the internal power MOSFETs, the switching frequency, and any external load on the VCC pin. It is
recommended that a small filter shown in Figure 14 be used for the VIN input to suppress transients which may
occur at the input supply. This is particularly important when VIN is operated close to the maximum operating
rating of the LM5015.
High Voltage VCC Regulator
The LM5015 VCC Low Drop Out (LDO) regulator allows the LM5015 to operate at the lowest possible input
voltage. When power is applied to the VIN pin and the EN pin voltage is greater than 0.45V, the VCC regulator is
enabled, supplying current into the external capacitor connected to the VCC pin. When the VIN voltage is
between 4.25V and 6.9V, the VCC voltage is approximately equal to the VIN voltage. When the voltage on the
VIN pin exceeds 6.9V, the VCC pin voltage is regulated at 6.9V. The total input operating range of the VCC LDO
regulator is 4.25V to 75V.
The output of the VCC regulator is current limited to 20mA. During power-up, the VCC regulator supplies current
into the required decoupling capacitor (0.47 µF or greater ceramic capacitor) at the VCC pin. When the voltage at
the VCC pin exceeds the VCC UVLO threshold of 3.75V and the EN pin is greater than 1.26V the PWM
controller is enabled and switching begins. The controller remains enabled until VCC falls below 3.60V or the EN
pin falls below 1.16V.
An auxiliary supply voltage can be applied to the VCC pin to reduce the IC power dissipation. If the auxiliary
voltage is greater than 6.9V, the internal regulator will essentially shutoff, and internal power dissipation will be
decreased by the VIN-VCC voltage difference times the operating current. The externally applied VCC voltage
should not exceed 14V. The VCC regulator series pass MOSFET includes a body diode (see Figure 13) between
VCC and VIN that should not be forward biased in normal operation. Therefore, the auxiliary VCC voltage should
never exceed the VIN voltage.
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