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Typical Performance Characteristics
LM2619MTC, Circuit of
Figure 3
, V
IN
= 3.6V, T
A
= 25C,
unless otherwise noted. (Continued)
Efficiency vs Output Current
(V
OUT
= 1.8V, PFM MODE)
Figure 1
)
Efficiency vs Output Current
(V
OUT
= 1.8V, PFM MODE, with Diode)
(Circuit in
Figure 1
)
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20065136
Device Information
The LM2619MTC is a simple, step-down DC-DC converter
optimized for powering circuits in mobile phones, portable
communicators, and similar battery powered RF devices. It
is based on a current-mode buck architecture, with synchro-
nous rectification in PWM mode for high efficiency. It is
designed for a maximum load capability of 500mA in PWM
mode. Maximum load range may vary from this depending
on input voltage, output voltage and the inductor chosen.
The device has all three of the pin-selectable operating
modes required for powering circuits in mobile phones and
other sophisticated portable devices with complex power
management needs. Fixed-frequency PWM operation offers
full output current capability at high efficiency while minimiz-
ing interference with sensitive IF and data acquisition cir-
cuits. During standby operation, hysteretic PFM mode re-
duces quiescent current to 160μA typ. to maximize battery
life. Shutdown mode turns the device off and reduces battery
consumption to 0.02μA (typ).
DC PWM mode feedback voltage precision is
±
2%. Effi-
ciency is typically 93% for a 200mA load with 3.6V output,
4.2V input. The efficiency can be increased for lower output
voltages like 1.5V,1.8V by using a schottky diode like
MBRM120L as shown in
Figure 4
. PWM mode quiescent
current is 600μA typ. The output voltage can be set from
1.5V to 3.6V by using external feedback resistors.
Additional features include soft-start, current overload pro-
tection, over voltage protection and thermal shutdown pro-
tection.
The LM2619MTC is constructed using a 14-pin TSSOP
package. Use of a high switching frequency (600kHz) re-
duces the size of external components.
CIRCUIT OPERATION
Referring to
Figure 4
,
Figure 5
,
Figure 6
and
Figure 7
,
the LM2619MTC operates as follows. During the first part of
each switching cycle, the control block in the LM2619MTC
turns on the internal PFET switch. This allows current to flow
from the input through the inductor to the output filter capaci-
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FIGURE 4. Typical Operating Circuit for 3.6V Output Voltage
L
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PrintDate=2003/08/20 PrintTime=18:54:05 801627bc ds200651_p Rev. No. 1.25
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