Texas Instruments LM5161, User Manual, Page: 6 / 19

UV2
IN, UVLO(rising) UVLO(TH)
UV1
R
V V 1
R
§ ·
¨ ¸
© ¹
IN(HYS) UVLO(HYS) UV2
V I R
u
OUT FB2
FB1 REF
V R
1
R V
OUT
SW
10
ON
V
F Hz
1.008 x 10 x R
Test Setup and Operation
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6 SNVU504A – August 2016 – Revised August 2016
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LM5161 Buck EVM User’s Guide
Figure 1. Buck EVM Setup
3.2 Operation
In order to maintain proper operation of the LM5161PWPBKEVM, the input voltage applied across J1
should be gradually increased. The load at the output (J2) should not exceed 1 A. The inductor L2 used in
this board is optimized for small solution size. The saturation current rating (I
SAT
) of the inductor should be
higher than the LM5161 integrated high-side FET peak current-limit threshold of 1.9 A (max.).
The nominal switching frequency (in Hz) can be set using the R
ON
(R1 in the EVM) resistor, as shown in
Equation 1 :
(1)
The output voltage is set by using the feedback divider resistors R8 (R
FB1
) and R7 (R
FB2
) in the EVM by
using Equation 2 :
(2)
The EN/UVLO resistors R9 (R
UV1
) and R3 (R
UV2
) in the EVM sets the input undervoltage lockout threshold
and the EN/UVLO hysteresis according to Equation 3 :
(3)
and,
(4)
where I
UVLO(HYS)
= 20 µA and V
UVLO(TH)
= 1.24 V.
Table 2 summarizes the LM5161 Buck EVM Jumper (JP1) settings that determine the desired modes of
operation.
• Forced continuous conduction mode (CCM) or FPWM
• Discontinuous conduction mode (DCM)