MTS62C19A Datasheet, PDF (9/20 Pages) Microchip Technology – Dual Full-Bridge Motor Driver

MTS62C19A
3.2 PWM Current Control
The current level in each motor winding is controlled by
a PWM circuit with a fixed T_OFF time. The load current
flowing in the winding is sensed through an external
sensing resistor R_S, connected between the power
bridge's source pin SENSE (sources of transistors Na
and Nb) and GND.
V_REF
I0
I1
÷10
COMPIN
C_C
R_C
V_LOAD
Power
Bridge _Pa
Pb
One-Shot
Source
Disable
Na
Nb
RC
C_t
R_t
SENSE
R_S
OUTA
OUTB
FIGURE 3-2:
PWM Current Control Circuit Principle (Channel 1 Shown).
The voltage across R_S is compared to a fraction of the
reference voltage V_REF, chosen with the logic input bits
I0 and I1 (Table 3-3). The power bridge, and thus the
load current, can also be switched off completely when
both logic inputs are high. Note that any logic input left
unconnected will be treated as a high level (pull-up
resistor).
The maximum trip current for regulation, given for
I0 I1 = 00 is calculated in Equation 3-1.
EQUATION 3-1:
I_MAX = _1---V0----^R-_--^E---R^F----_S
TABLE 3-3:
I0
0
1
0
1
CURRENT LEVEL CONTROL TRUTH TABLE
I1
Comp. Trip Voltage
0
V_TRIP = 1/10 x V_REF
0
V_TRIP = 1/15 x V_REF
1
V_TRIP = 1/30 x V_REF
1
x
Output Current
I_MAX = V_REF/10R_S
2/3 x I_MAX = V_REF/15R_S
1/3 x I_MAX = V_REF/30R_S
0 (no current)
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DS22260C-page 9