lm5015mhx National Semiconductor Corporation, lm5015mhx Datasheet - Page 3

• Manufacturer Part Number: lm5015mhx
• Description: High Voltage Monolithic Two-switch Forward Dc-dc Regulator
• Manufacturer: National Semiconductor Corporation

Pin Descriptions
Pin
NA
10
11
12
13
14
1
2
3
4
5
6
7
8
9
COMP
AGND
PGND
Name
PVIN
VCC
CFB
BST
VIN
HO
RT
FB
LO
EN
SS
EP
Description
Analog ground
Oscillator frequency
programming and optional
synchronization input
Feedback input of the internal
error amplifier, for non-isolated
applications
Control input for the PWM
comparator
Current feedback pin
Power ground
Low side switch drain
Input supply pin for high side
switch
High side switch source
High side bootstrap bias
Bias regulator output, or input for
external bias supply
Analog input voltage pin
Enable / Under-Voltage Lock-
Out / Shutdown input
Soft-start
Exposed Pad
Application Information
Internal reference for the regulator control functions. The AGND pin and
the PGND pin should be connected directly to minimize switching noise and
prevent erratic operation.
The internal oscillator is set with a resistor between this pin and the AGND
pin. The recommended switching frequency range is 25KHz to 750 kHz.
The RT pin can accept synchronization pulses from an external clock. A
100 pF capacitor is recommended for coupling the synchronizing clock to
the RT pin.
This pin is connected to the inverting input of the internal error amplifier.
The 1.26V reference is internally connected to the non-inverting input of
the error amplifier. In isolated application using an external error amplifier,
this pin should be connected to the AGND pin.
Internally connected to the open drain output of the internal error amplifier.
COMP pull-up is provided by an internal 5 kΩ resistor which may be used
to bias an opto-coupler transistor in isolated applications.
Feedback in put for high bandwidth isolated applications. An NPN current
mirror couples the external opto-coupler current to the PWM comparator
while maintaining a relatively constant opto-coupler voltage.
Internally connected to the current sense resistor in the source of the low
side MOSFET switch.
The drain terminal of the internal low side power MOSFET.
Internally connected to the drain of the high side power MOSFET.
The source terminal of the high side power MOSFET.
An external capacitor is required between the BST and the HO pins. A
minimum capacitor value of 0.022 µF is recommended. The capacitor is
charged from VCC via an internal diode during the power MOSFET off-time.
VCC tracks VIN up to 6.9V. At higher VIN voltages, VCC is regulated to 6.9
Volts. A 0.47µF or greater ceramic decoupling capacitor is required on the
VCC pin. An external bias voltage between 7V and 14V applied to the VCC
pin will disable the internal VCC regulator, reduce internal power
dissipation, and improve the converter efficiency.
Power supply Input for the switching regulator control blocks.
An external voltage divider can be used to set the input under-voltage
lockout threshold. If the EN pin is left unconnected, a 6 µA pull-up current
source pulls the EN pin high to enable the regulator.
An internal 11 µA current source charges an external capacitor connected
to the SS pin to soft-start the switching regulator by gradually raising the
COMP pin voltage.
Exposed metal pad on the underside of the package. It is recommended to
connect this pad to the PGND and AGND pins, and also to the PC board
ground plane in order to improve heat dissipation.
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