DRV104

10

SBVS036A

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FIGURE 9. Non-Latching Fault Monitoring Circuit.

FIGURE 10. Latching Fault Monitoring Circuit.

FIGURE 11. Using an LED to Indicate a Fault Condition.

FIGURE 8. Simplified Duty Cycle Adjust Input.

The Duty Cycle Adjust pin is internally driven by an oscillator

frequency dependent current source and connects to the

input of a comparator, as shown in Figure 8. The DRV104’s

PWM adjustment is inherently monotonic; that is, a de-

creased voltage (or resistor value) always produces an

decreased duty cycle.

STATUS OK FLAG

The Status OK Flag (pin 13) provides a fault indication for

over-current and thermal shutdown conditions. During a fault

condition, the Status OK Flag output is driven Low (pin

voltage typically drops to 0.45V). A pull-up resistor, as shown

in Figure 9, is required to interface with standard logic. Figure

9 also gives an example of a non-latching fault monitoring

circuit, while Figure 10 provides a latching version. The

Status OK Flag pin can sink up to 10mA, sufficient to drive

external logic circuitry, a reed relay, or an LED (as shown in

Figure 11) to indicate when a fault has occurred. In addition,

the Status OK Flag pin can be used to turn off other

DRV104s in a system for chain fault protection.

Over-Current Fault

An over-current fault occurs when the PWM peak output

current is greater than typically 2.0A. The Status OK flag is

not latched. Since current during PWM mode is switched on

and off, the Status OK flag output will be modulated with

PWM timing (see the Status OK flag waveforms in the

Typical Characteristics).

Avoid adding capacitance to pins 6, 7 (OUT) because this

can cause momentary current limiting.

Over-Temperature Fault

A thermal fault occurs when the die reaches approximately

160

°C, producing an effect similar to pulling the input low.

Internal shutdown circuitry disables the output. The Status

OK Flag is latched in the Low state (fault condition) until the

die has cooled to approximately 140

°C.

2.75 • I

REF

R

PWM

+V

S

OSC

3.9V

1.3V

13

20k

Ω

+5V

Q

Q

CLR

OK

OK

OK Reset

J

CLK

GND

K

V

S

74XX76A

(1)

NOTE: (1) A small capacitor (10pF) may be required in noisy environments.

DRV104

Thermal Shutdown

Over-Current

8, 9

V

PS

6, 7

OUT

PWM

Status OK Flag

5k

Ω

+5V

Status OK Flag

(LED)

HLMP-Q156

13

DRV104

Thermal Shutdown

Over-Current

6, 7

8, 9

V

PS

OUT

PWM

DRV104

Thermal Shutdown

Over-Current

PWM

6, 7

8, 9

13

OUT

V

PS

5k

Ω

Pull-Up

+5V

Status OK Flag

TTL or HCT