Datasheet

FB
GND
SW
EN
VOUT
L1
D1
R1
R2
VINA/VIND
C1 C4
U1
C2
GND
EN
2
6
4, 5
1
3
R3
Chf
2.2 PF
VIN
C3
GND
22 PF
20k
10k
2.2 PF
22 PF
22 nF
(opt.)
1.0 PH
3.3 PH
(³;´YHUVLRQ)
1.8V
0
0
V
IN
V
D
T
ON
t
t
Inductor
Current
D = T
ON
/T
SW
V
SW
T
OFF
T
SW
I
L
I
PK
SW
Voltage
LMR10510
www.ti.com SNVS727B –OCTOBER 2011–REVISED APRIL 2013
Figure 21. Typical Waveforms
SOFT-START
This function forces V
OUT
to increase at a controlled rate during start up. During soft-start, the error amplifier’s
reference voltage ramps from 0V to its nominal value of 0.6V in approximately 600 µs. This forces the regulator
output to ramp up in a controlled fashion, which helps reduce inrush current.
OUTPUT OVERVOLTAGE PROTECTION
The over-voltage comparator compares the FB pin voltage to a voltage that is 15% higher than the internal
reference V
REF
. Once the FB pin voltage goes 15% above the internal reference, the internal PMOS control
switch is turned off, which allows the output voltage to decrease toward regulation.
UNDERVOLTAGE LOCKOUT
Under-voltage lockout (UVLO) prevents the LMR10510 from operating until the input voltage exceeds 2.73V
(typ). The UVLO threshold has approximately 430 mV of hysteresis, so the part will operate until V
IN
drops below
2.3V (typ). Hysteresis prevents the part from turning off during power up if V
IN
is non-monotonic.
CURRENT LIMIT
The LMR10510 uses cycle-by-cycle current limiting to protect the output switch. During each switching cycle, a
current limit comparator detects if the output switch current exceeds 1.75A (typ), and turns off the switch until the
next switching cycle begins.
THERMAL SHUTDOWN
Thermal shutdown limits total power dissipation by turning off the output switch when the IC junction temperature
exceeds 165°C. After thermal shutdown occurs, the output switch doesn’t turn on until the junction temperature
drops to approximately 150°C.
Figure 22. Typical Application Schematic
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