Datasheet

V
OUT
V
IN
V
IN
2.7V to 5.6V*
GND
LM2750-ADJ
C
IN
2.2 PF
C
OUT
2.2 PF
8, 9 1, 2
5, 6, DAP
Capacitors: 1.0PF - TDK C1608X5R1A105K
2.2PF - TDK C2012X7R1A225K
V
OUT
= 1.23V × (1 + R1/R2)
V
OUT
Range: 3.8V to 5.2V
I
OUT
up to 120mA
CAP+
CAP-
C
FLY
1 PF
10
7
SD
4
FB
3
R1
R2
For V
OUT
< 4.9V:
max V
IN
= V
OUT
+ 0.7V
LM2750
SNVS180L –APRIL 2002–REVISED MAY 2013 www.ti.com
THERMAL SHUTDOWN
The LM2750 implements a thermal shutdown mechanism to protect the device from damage due to overheating.
When the junction temperature rises to 150ºC (typ.), the part switches into shutdown mode. The LM2750
releases thermal shutdown when the junction temperature of the part is reduced to 130ºC (typ.).
Thermal shutdown is most-often triggered by self-heating, which occurs when there is excessive power
dissipation in the device and/or insufficient thermal dissipation. LM2750 power dissipation increases with
increased output current and input voltage (see POWER EFFICIENCY AND POWER DISSIPATION section).
When self-heating brings on thermal shutdown, thermal cycling is the typical result. Thermal cycling is the
repeating process where the part self-heats, enters thermal shutdown (where internal power dissipation is
practically zero), cools, turns-on, and then heats up again to the thermal shutdown threshold. Thermal cycling is
recognized by a pulsing output voltage and can be stopped be reducing the internal power dissipation (reduce
input voltage and/or output current) or the ambient temperature. If thermal cycling occurs under desired operating
conditions, thermal dissipation performance must be improved to accommodate the power dissipation of the
LM2750. Fortunately, the WSON package has excellent thermal properties that, when soldered to a PCB
designed to aid thermal dissipation, allows the LM2750 to operate under very demanding power dissipation
conditions.
OUTPUT CURRENT LIMITING
The LM2750 contains current limit circuitry that protects the device in the event of excessive output current
and/or output shorts to ground. Current is limited to 300mA (typ.) when the output is shorted directly to ground.
When the LM2750 is current limiting, power dissipation in the device is likely to be quite high. In this event,
thermal cycling should be expected (see THERMAL SHUTDOWN section).
PROGRAMMING THE OUTPUT VOLTAGE OF THE LM2750-ADJ
As shown in the application circuit of Figure 14, the output voltage of the LM2750-ADJ can be programmed with
a simple resistor divider (see resistors R1 and R2). The values of the feedback resistors set the output voltage,
as determined by the following equation:
V
OUT
= 1.23V × (1 + R1/ R2)
In the equation above, the "1.23V" term is the nominal voltage of the feedback pin when the feedback loop is
correctly established and the part is operating normally. The sum of the resistance of the two feedback resistors
should be between 15kΩ and 20kΩ:
15kΩ < (R1 + R2) < 20kΩ
If larger feedback resistors are desired, a 10pF capacitor should be placed in parallel with resistor R1.
Figure 14. LM2750-ADJ Typical Application Circuit
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