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LM3150MH Datasheet, PDF (14/26 Pages) Texas Instruments – LM3150 SIMPLE SWITCHER CONTROLLER, 42V Synchronous Step-Down
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LM3150
SNVS561D – SEPTEMBER 2008 – REVISED MARCH 2011
www.ti.com
Inductor Designator
L26
L27
L28
L29
L30
L31
L32
L33
L34
L35
L36
L37
L38
L39
L40
L41
L42
L43
L44
L45
L46
L47
L48
Table 1. Inductor Selection Table (continued)
Inductance
(µH)
15
10
6.8
4.7
3.3
2.2
1.5
1
0.68
0.47
0.33
22
15
10
6.8
4.7
3.3
2.2
1.5
1
0.68
0.47
0.33
Current
(A)
12-15
12-15
12-15
12-15
12-15
12-15
12-15
12-15
12-15
12-15
12-15
15-
15-
15-
15-
15-
15-
15-
15-
15-
15-
15-
15-
Part Name
SER2814L-103KL
7447709006
7447709004
MLC1245-152
DO3316H-681
DR73-R33-R
SER2817H-153KL
SER2814H-103KL
SER2013-472ML
SER2013-362L
HA3778–AL
B82477-G4102-M
Vendor
COILCRAFT
WURTH
WURTH
COILCRAFT
COILCRAFT
COOPER
COILCRAFT
COILCRAFT
COILCRAFT
COILCRAFT
COILCRAFT
EPCOS
5. Determine Output Capacitance
Typical hysteretic COT converters similar to the LM3150 require a certain amount of ripple that is generated
across the ESR of the output capacitor and fed back to the error comparator. Emulated Ripple Mode control built
into the LM3150 will recreate a similar ripple signal and thus the requirement for output capacitor ESR will
decrease compared to a typical Hysteretic COT converter. The emulated ripple is generated by sensing the
voltage signal across the low-side FET and is then compared to the FB voltage at the error comparator input to
determine when to initiate the next on-time period.
COmin = 70 / (fs2 x L)
(17)
The maximum ESR allowed to prevent over-voltage protection during normal operation is:
ESRmax = (80 mV x L x Af) / ETmin
(18)
ETmin is calculated using VIN-MIN
Af = VOUT / 0.6 if there is no feed-forward capacitor used
Af = 1 if there is a feed-forward capacitor used
The minimum ESR must meet both of the following criteria:
ESRmin ≥ (15 mV x L x Af) / ETmax
ESRmin ≥ [ ETmax / (VIN - VOUT) ] x (Af / CO)
(19)
(20)
ETmax is calculated using VIN-MAX.
Any additional parallel capacitors should be chosen so that their effective impedance will not negatively attenuate
the output ripple voltage.
6. Determine The Use of Feed-Forward Capacitor
Certain applications may require a feed-forward capacitor for improved stability and easier selection of available
output capacitance. Use the following equation to calculate the value of Cff.
14
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