L6910 STMicroelectronics, L6910 Datasheet - Page 14

• Manufacturer Part Number: L6910
• Description: IC PWM BUCK BST VM 16SOIC
• Manufacturer: STMicroelectronics

Specifications of L6910

• Pwm Type: Voltage Mode
• Number Of Outputs: 1
• Frequency - Max: 230kHz
• Duty Cycle: 100%
• Voltage - Supply: 5 V ~ 12 V
• Buck: Yes
• Boost: Yes
• Flyback: No
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: No
• Operating Temperature: -40°C ~ 150°C
• Package / Case: 16-SOIC (3.9mm Width)
• Frequency-max: 230kHz
• Output Voltage: 4 V
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: 497-3656-5; 497-4220-5; 497-4220-5

L6910 - L6910A
Figure 16. Efficiency vs Output Current
6
6.1 Inductor Selection
To select the right inductor value, the application conditions must be fixed. For example we can consider:
Vin=12V Vout =3.3V Iout=15A
Considering a ripple of approximately 25% to 30% of Iout, the inductor value will be L=3 H.
An iron powder core (TO50-52B) with 7 windings has been chosen.
6.2 Output Capacitors
2 POSCAP capacitors, model 6TPB330M, have been chosen, with a maximum ERS equal to 40m
Therefore, the resultant ESR is of 20m . Considering a current ripple of 4A, the output voltage ripple is:
6.3 Input Capacitors
For I
to 7.5A.
Two OSCON electrolytic capacitors 6SP680M, with a maximum ESR equal to 13m , have been chosen to sus-
tain the ripple. Therefore, the resultant ESR is equal to 13m /2 = 6.5m . The losses, in worst case, are:
6.4 Over-Current Protection
The current limit can be set to approximately 20A. Substituting the demo board parameters in the relation-
ship reported in the relative section, (I
that R
14/29
OUT
COMPONENTS SELECTION
OCS
= 15A and D = 0.5 (worst case for input current ripple), the RMS current of the input capacitor is equal
= 510
100
95
90
85
80
75
70
65
60
55
50
1
3
Vin=Vcc=12V
Vin=Vcc=12V
Fsw.=200KHZ
Fsw.=200KHZ
OSCMIN
5
Vout = 4 · 0.02 = 80mV
P = ESR · I
=170 A; IP = 20A; R
7
Output Current (A)
Output Current (A)
2
rms = 366mW
9
11
DSONMAX
13
= 9m
15
Vo=3.3V
Vo=3.3V
Vo=1.5V
Vo=1.5V
Vo=1.8V
Vo=1.8V
Vo=2.5V
Vo=2.5V
Vo=1.2V
Vo=1.2V
Vo=5V
Vo=5V
Vo=0.9V
Vo=0.9V
/ 2=4.5m
17
it results
each.