FMS7401 Datasheet, PDF (38/80 Pages) Fairchild Semiconductor – Digital Power Controller

FMS7401/7401L
PRODUCT SPECIFICATION
The PWM Timer 1 can be programmed to toggle one or both PWM output signals (T1HS1 and T1HS2) to support a variety of
output configurations (half bridge, full bridge,⁸ low side or high side driving). These outputs may be used to drive an external
half-bridge driver and are enabled by programming the T1C1 and T1C2 bits in the T1CNTRL register (see Table 16). The
T1HS1 (G0) and T1HS2 (G5) output signals may be configured with opposite phases and dead time controlled edges (see
Figure 12). The phases of the output signals are configured by the bits of the PORTGD I/O configuration register.⁹ Upon device
power-up, the T1HS1 and T1HS2 signals may be programmed to default as active high/low outputs by the default I/O configu-
ration register bits in the non-volatile Initialization Register 4.¹⁰ Both G0/T1HS1 and G5/T1HS2 pins will configure to their
programmed default state after TDIO2 from the system reset trigger (e.g. from a POR). The G0/T1HS1 and G5/T1HS2 pins may
both be configured as outputs with common or opposite phases. If configured as outputs, the PORTGD[0] and PORTGD[5] bits
configure the T1HS1 and T1HS2 signals as active high or low. If the PORTGD bit is 0, the output signal is active high, other-
wise it is active low. The PORTGD[1] bit also configures the G1/ADSTROBE pin as an active high/low signal once configured
as an output. The Initialization Register 4 bits only default the G0/T1HS1 and G5/T1HS2 pins not the G1/ADSTROBE pin.
From factory, the G0/T1HS1, G5/T1HS2 and G1/ADSTROBE device pins are defaulted as tri-stated inputs. The pins must be
configured by the Initialization Register 4 bits or by software directly through the PORTGC and PORTGD register as an output
port before enabling the TMR1 counter and its outputs.
The dead time counter of the Timer 1 circuit controls the dead time (TDT) delay between the T1HS1 and T1HS2 output edge
transitions through the DT[4:0] bits of the DTIME register. The dead time counter delay is first triggered after the TMR1
counter equals to the T1CMPA value and the T1HS1 signal transitions from its resting (off) to its active (on) state. Once the
programmed TDT completes, the T1HS2 signal then transitions from its resting (off) to its active (on) state. The dead time
counter delay is triggered for a second time after the TMR1 counter equals to the T1RA value and the T1HS2 signal transitions
from its active (on) to its resting (off) state. Once the programmed TDT completes, the T1HS1 signal then transitions from its
active (on) to its resting (off) state ending the PWM cycle. The PWM cycle is considered complete once the TMR1 counter
completes the T1RA count plus TDT even in the T1HS1 and T1HS2 outputs are disabled.
The T1HS1 and T1HS2 PWM output signals may be programmed to be automatically disabled by the output of the digital filter
(PWMOFF) in Programmable Comparator circuit. The output may be programmed to disable the Timer 1 circuit completely or
disable only the current PWM cycle. Refer to the Programmable Comparator Circuit section of the datasheet for details.
The Timer 1’s ADSTROBE output signal may be configured as the G1/ADSTROBE device output if the T1BOUT bit of the
T1CNTRL register is set. The ADSTROBE signal, however, is always generated by the Timer 1 circuit. Initially, the
ADSTROBE begins its PWM cycle at its resting (off) state and transitions to its active (on) state once the TMR1 counter com-
pletes its count equal to the T1CMPB value. The active (on) edge transition of the ADSTROBE output may be programmed to
automatically trigger an ADC conversion cycle if the ENDAS bit of the ADCNTRL2 register is set. Refer to the ADC Circuit
section of the datasheet for details.
The T1PND bit of the T1CNTRL register is set once the TMR1 counter completes the count equal to the T1RA value (over-
flows). Software may use the T1PND bit to monitor the PWM cycles and/or trigger microcontroller hardware interrupts
(TMRI1) if the T1EN bit of the T1CNTRL register is set. Software must clear the T1PND bit in order to detect a new overflow
condition and/or trigger a new interrupt.⁶
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REV. 1.0.2 6/23/04