EVAL6208N Datasheet, PDF (9/27 Pages) STMicroelectronics – DMOS DRIVER FOR BIPOLAR STEPPER MOTOR

Figure 5. Overcurrent Detection Timing Definition
I_OUT
I_SOVER
L6208
ON
BRIDGE
OFF
V_EN
90%
10%
t_OCD(ON)
t_OCD(OFF)
D02IN1399
CIRCUIT DESCRIPTION
POWER STAGES and CHARGE PUMP
The L6208 integrates two independent Power MOS Full Bridges. Each Power MOS has an R_DS(ON) = 0.3Ω (typ-
ical 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 (t_DT = 1µs typical value) between the switch off and switch on of two Power MOSFETSs in one leg of
a bridge.
Pins VS_A and VS_B MUST be connected together to the supply voltage V_S. The device operates with a supply
voltage in the range from 8V to 52V. It has to be noticed that the R_DS(ON) increases of some percents when the
supply voltage is in the range from 8V to 12V (see Fig. 34 and 35).
Using N-Channel Power MOS for the upper transistors in the bridge requires a gate drive voltage above the
power supply voltage. The bootstrapped supply voltage V_BOOT is obtained through an internal Oscillator and few
external components to realize a charge pump circuit as shown in Figure 6. The oscillator output (VCP) is a
square wave at 600KHz (typical) with 10V amplitude. Recommended values/part numbers for the charge pump
circuit are shown in Table 1.
Table 1. Charge Pump External Components Values
C_BOOT
220nF
C_P
10nF
R_P
100Ω
D1
1N4148
D2
1N4148
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