MTS2916A
DS22259C-page 10 2010-2013 Microchip Technology Inc.
When the maximum allowed current is reached, the
bridge source is turned off during a fixed period T
OFF
(typically 50 µs) given by a non-retriggerable pulse
generator and the external timing components R
t
(20k-100 k range) and C
t
(100 pF-1000 pF range):
EQUATION 3-2:
During T
OFF,
the winding current decreases. When the
driver is re-enabled, the winding current increases
again until it reaches the threshold, and the cycle
repeats itself, maintaining the load current at the
desired level.
FIGURE 3-3: PWM Output Current
Waveform.
3.3 Circuit Protection
A thermal protection circuitry turns off all drivers when
the junction temperature exceeds a safe operating limit
of +170°C (typical). This protects the devices from
failure due to excessive heating. Despite this thermal
protection, output short circuits are not permitted. The
output drivers are re-enabled once junction
temperature has dropped below +145°C (typical).
FIGURE 3-4: Thermal Shutdown Output
vs. Temperature Showing Hysteresis.
An undervoltage lockout circuit protects the MTS2916A
from potential shoot-through currents when the load
supply voltage is applied prior to the logic supply volt-
age. The power bridge and all outputs are disabled if
V
LOGIC
is smaller than 4V.
With this protection feature, the circuit will withstand
any order of turn-on or turn-off of the supply voltages
V
LOGIC
and V
LOAD
. Normal dV/dt values are assumed.
F
i
g
u
r
e
5
.
2
:
T
OFF
1.1 R
t
C
t
=
PHASE
I
OUT
+
0
I
OUT
t
off
t
d
t
on
-
1
0
+170°C
+145°C
thshtd_en
