LM8333

SNLS246K – SEPTEMBER 2006 – REVISED MAY 2013

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PWM Output with Programmable Duty Cycle

The PWM pin may be used either as a pulse-width modulated output driven by a 16-bit timer or as a general-

purpose output pin. In the PWM mode, the low time (TLO) and high time (THI) are programmable between 1 × tC

and 65K × tC cycles in which tC is the cycle time (nominally 1 microsecond), as shown in Figure 5. The period

TPD is the sum of THI and TLO. The PWM_LO command writes TLO, and the PWM_HI command writes THI.

Operational modes of the PWM pin are controlled by the PWM_CTL command. Before activating the PWM

output, the TLO and THI times must be initialized. Figure 6 shows the command formats.

Figure 5. Programmable PWM

Figure 6. PWM Control Commands for Arbitrary Duty Cycle

Table 3. Summary of PWM Control Bits

OUT_DIR Bit

PWM_DIR Bit

MOD BIT

Description

0

1

0

Drive output low

1

1

0

Drive output high

0

0

0

TRI-STATE® mode

X

X

1

PWM timer output

General-Purpose I/O (GPIO)

Figure 7 shows the commands to write, read and control the general-purpose I/O port pins, GEN_IO_0,

GEN_IO_1, GEN_IO_2, and GEN_IO_3.

All general-purpose I/O pins can be programmed as inputs or outputs as shown in Table 4. The GEN_IO_0 and

GEN_IO_1 pins provide an additional capability for programmable wake-up.

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