LMZ36002_16 Datasheet, PDF (14/36 Pages) Texas Instruments – SIMPLE SWITCHER 4.5V to 60V Input, 2-A Power Module

LMZ36002
SNVSA92A – SEPTEMBER 2015 – REVISED SEPTEMBER 2015
www.ti.com
7.3.2 Switching Frequency (RT)
The switching frequency range of the LMZ36002 is 200 kHz to 1 MHz. Not all PV_IN, V_OUT, and I_OUT conditions
can be set to all of the frequencies in this range. See Recommended Operating Range for the allowable
operating ranges. The switching frequency can easily be set one of three ways. First, leaving the RT pin (pin 9)
and RTSEL pin (pin 10) floating (OPEN) allows operation at the default switching frequency of 500 kHz. Also,
connecting the RTSEL pin to AGND while floating the RT pin, sets the switching frequency to 1 MHz. The option
is also available to set the switching frequency to any frequency in the range of 200 kHz to 1 MHz, by connecting
a resistor (R_RT) between the RT pin and AGND, while floating the RTSEL pin. See Table 3 below for standard
resistor values for setting the switching frequency or use Equation 2 to calculate R_RT for additional switching
frequencies.
Table 3. Switching Frequency R_RT Values
Switching Frequency
250 kHz
R_RT (kΩ)
158
500 kHz
78.7 or (RT pin OPEN, RTSEL pin OPEN)
750 kHz
53.6
1 MHz
38.3 or (RT pin OPEN, RTSEL pin to AGND)
40200
R_RT =
0.6 (k )
Fsw (kHz)
(2)
7.3.3 Recommended Operating Range
Table 4 and Table 5 below show the allowable switching frequencies for a given range of output voltages.
Reference Table 4 for applications where the maximum output current is 1.75 A or less. Reference Table 5 for
applications that the output current is greater than 1.75 A. Notice that applications requiring less than 1.75 A can
operate over a much wider range of switching frequencies. For the most efficient solution, always operate at the
lowest allowable frequency.
V_OUT RANGE (V)
2.5 - 3.5 V
>3.5 - 4.5 V
>4.5 - 5.5 V
>5.5 - 6.5 V
>6.5 - 7.5 V
Table 4. Switching Frequency vs Output Voltage
Output Current ≤ 1.75 A
PVIN = 12 V
MIN
MAX
200
1000
200
1000
200
1000
300
1000
300
900
SWITCHING FREQUENCY RANGE (kHz)
PVIN = 24 V
PVIN = 36 V
MIN
MAX
MIN
MAX
200
600
200
400
200
850
200
550
200
1000
200
750
200
1000
200
1000
300
1000
300
950
PVIN = 48 V
MIN
MAX
200
300
200
400
200
550
200
630
300
800
V_OUT RANGE (V)
2.5 - 3.5 V
>3.5 - 4.5 V
>4.5 - 5.5 V
>5.5 - 6.5 V
>6.5 - 7.5 V
Table 5. Switching Frequency vs Output Voltage
Output Current > 1.75 A
PVIN = 12 V
MIN
MAX
200
450
200
500
200
500
300
500
300
400
SWITCHING FREQUENCY RANGE (kHz)
PVIN = 24 V
PVIN = 36 V
MIN
MAX
MIN
MAX
200
500
200
400
200
600
200
550
200
650
200
700
250
700
250
800
300
750
300
800
PVIN = 48 V
MIN
MAX
200
300
200
400
200
550
250
650
300
800
14
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