Datasheet

L6226 Circuit description
Doc ID 9452 Rev 4 11/31
4 Circuit description
4.1 Power stages and charge pump
The L6226 integrates two independent Power MOS full bridges. Each Power MOS has an
R
DSon
= 0.73 Ω (typical value @ 25 °C), with intrinsic fast freewheeling diode. Cross
conduction protection is achieved using a dead time (td = 1μs typical) between the switch off
and switch on of two Power MOS in one leg of a bridge. Using N channel power MOS for the
upper transistors in the bridge requires a gate drive voltage above the power supply voltage.
The Bootstrapped (VBOOT) supply is obtained through an internal oscillator and few
external components to realize a charge pump circuit as shown in Figure 5. The oscillator
output (VCP) is a square wave at 600 kHz (typical) with 10 V amplitude. Recommended
values/part numbers for the charge pump circuit are shown in Table 6.
Figure 5. Charge pump circuit
4.2 Logic inputs
Pins IN1A, IN2A, IN1B, IN2B, ENA and ENB are TTL/ CMOS and microcontroller compatible
logic inputs. The internal structure is shown in Figure 4. Typical value for turn-on and turn-off
thresholds are respectively Vthon=1.8V and Vthoff = 1.3V. Pins EN
A and ENB are commonly
used to implement Overcurrent and Thermal protection by connecting them respectively to
the outputs OCD
A and OCDB, which are open-drain outputs. If that type of connection is
chosen, some care needs to be taken in driving these pins. Two configurations are shown in
Figure 7 and Figure 8. If driven by an open drain (collector) structure, a pull-up resistor R
EN
and a capacitor CEN are connected as shown in Figure 7. If the driver is a standard Push-
Pull structure the resistor R
EN and the capacitor CEN are connected as shown in Figure 8.
The resistor R
EN should be chosen in the range from 2.2 kΩ to 180 kΩ. Recommended
values for R
EN and CEN are respectively 100 kΩ and 5.6 nF. More information on selecting
the values is found in the overcurrent protection section.
Table 6. Charge pump external components values
C
BOOT
220 nF
C
P
10 nF
D1 1N4148
D2 1N4148
9
6
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96
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