ST7MC2N6 View Datasheet(PDF) - STMicroelectronics

Part Name

Description

Manufacturer

ST7MC2N6

8-bit MCU with nested interrupts, Flash, 10-bit ADC, brushless motor control, five timers, SPI, LINSCI™

STMicroelectronics 

ST7MC1xx/ST7MC2xx

MOTOR CONTROLLER (Cont’d)

Figure 113. Dead Time waveform with delay greater than the positive PWM pulse

Input

Output A

Output B

5V

0V

5V

0V

5V

0V

Delay

Table 52. Dead time programming and example

DTG5 DTG4

Tdtg

Deadtime expression

Deadtime value

Tdtg

Dead time range

@16MHz Fmtc @ 16MHz Fmtc

0

X 2xTmtc (DTG[4..0]+1) x Tdtg From 1 to 32 Tdtg

125ns

0.125µs to 4µs

1

1

0

1

4xTmtc

8xTmtc

(DTG[3..0]+17) x Tdtg

From 17 to 32 Tdtg

250ns

500ns

4.25µs to 8µs

8.5µs to 16µs

The deadtime delay is the same for each of the

channels and is programmable with the DTG[5..0]

bits in the MDTG register.

The resolution is variable and depends on the

DTG5 and DTG4 bits. Table 52 summarizes the

set-up of the deadtime generator.

ITmtc is the period of the Dead Time Generator in-

put clock (Fmtc = 16 MHz in most cases, not affect-

ed by the XT16:XT8 prescaler bits in the MCONF

register).

For safety reasons and since the deadtime de-

pends only on external component characteristics

(level-shifter delay, power components switching

duration,...) the register used to set-up deadtime

duration can be written only once after the MCU

reset. This prevents a corrupted program counter

modifying this system critical set-up, which may

cause excessive power dissipation or destructive

shoot-through in the power stage half bridges.

When using the three independent U, V and W

PWM signals (PCN bit set) (see Figure 114) to

drive the MCOx outputs, deadtime is added as

shown in Figure 111.

The dead time generator is enabled/disabled us-

ing the DTE bit.

The effect of the DTE bit depends on the PCN bit

value.

If the PCN bit is set:

■ DTE is read only. To reset it, first reset the PCN

bit, then reset DTE and set PCN to 1 again.

■ If DTE=0, the high and low side outputs are

simply complemented (no deadtime insertion,

DTG[5:0] bits are not significant); this is to allow

the use of an external dead time generator.

Note: The reset value of the MDTG register is FFh

so when configuring the dead time, it is mandatory

to follow one the two following sequences:

■ To use dead t imes while the PCN bit is set; from

reset state write the MDTG value at once. The

DTE bit will be read back as 1 whatever the

programming value (read only if PCN=1)

■ To use dead times while the PCN bit is reset,

write first the dead time value in DTG[5:0], then

reset the PCN bit, or do both actions at the same

time.

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