L6228Q View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'L6228Q' PDF : 32 Pages View PDF
L6228Q
4
Circuit description
Circuit description
4.1
Power stages and charge pump
The L6228Q integrates two independent power MOSFET full-bridges. Each power MOSFET
has an RDS(on) = 0.73 Ω (typical value @ 25 °C), with intrinsic fast freewheeling diode.
Switching patterns are generated by the PWM current controller and the phase sequence
generator (see below). Cross conduction protection is achieved using a dead time (tDT = 1 μs
typical value) between the switch off and switch on of two power MOSFETs in one leg of a
bridge.
VSA and VSB pins must be connected together to the supply voltage VS. The device
operates with a supply voltage in the range from 8 V to 52 V. It has to be noticed that the
RDS(on) increases of some percents when the supply voltage is in the range from 8 V to 12
V.
Using N-channel power MOSFETs for the upper transistors in the bridge requires a gate
drive voltage above the power supply voltage. The bootstrapped supply voltage VBOOT is
obtained through an internal oscillator and few external components to realize a charge
pump circuit as shown in Figure 8. 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.
Table 6.
Charge pump external component values
Component
CBOOT
CP
D1
D2
Value
220 nF
10 nF
1N4148
1N4148
Figure 8. Charge pump circuit
VS
D1
D2
CBOOT
CP
VCP VBOOT
VSA VSB
D01IN1328
Doc ID 14321 Rev 5
11/32
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