FAN8048 データシートの表示（PDF） - Fairchild Semiconductor

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FAN8048

2 DC-DC Converter & 4-CH PWM Motor IC

Fairchild Semiconductor 

FAN8048

Application Information

1. System Control and Protection Functions

1-1. System Enable/Disable Function

As shown in Figure 1, system enable ON (pin4) should be set low (typically under VIN - 0.65V) only once until OFF (pin3)

receives the disable signal (typically under VSYS1 - 0.85V), then all circuits remain in enable status.

Also, to prevent malfunction, this function activates when the circuit short condition exists such as over current or circuit

shorts, the whole circuit becomes the disable.

When the circuit is enabled, to obtain the necessary power (VG) to operate the internal circuits and upper side output power

switches of the 4 channels H-bridge driver, the VG converter circuit is activated. Also, to stably operate all circuits, the VG

converter keeps other circuits from activating until the output voltage of the VG converter reaches the specific voltage (3.9V).

When the output voltage of the VG converter reaches 3.9V, the first DC-DC converter (DC-DC Converter1) activate. And

when output voltage of DC-DC converter1(VSYS1) reaches 1.35V, the second converter (DC-DC Converter2) activates in

sequence. The circuit activation sequence as stated above and a flow chart are shown in Figure 3 and Figure 4.

1-2. Channel Mute Function

When MUTE (pin29) is high (typically above 2.2V), the mute circuit activates, so the all motor driver (4 channels H-bridge

driver) outputs are in mute state; on the other hand, when it is low (under 0.5V), mute state is off.

1-3. Thermal Shut Down(TSD) Function

This thermal shutdown (TSD) function is designed to protect the chip from being damaged as the chip's internal temperature

rises. If the TSD circuit activates, all motor driver (4 channel H-bridge drivers) outputs are in mute state. When the chip's

internal temperature reaches 150°C (typical), then the TSD circuit is activated, and when the chip temperature falls to 130°C or

below, the TSD circuit is deactivated and the output drivers operate normally.

MUTE 29

Mute Circuit

Channel Mute

125℃ 150℃

TSD

Short Circuit Detector

VSYS1

EA1O 10

1.35V

CSPRT

OFF 3

SPRT

5

VSYS1 22

ON 4

VG 1

R1

R2

Vref1

6uA

12uA

System_OFF

0.5V

VSYS1<1.65V

Start_up

Circuit System_ON

Bias &

Refernece

System_ON

Bias

DC-DC Converter

Wake-up Singnal

DC-DC

Converter

VG Converter

Figure 1. Block Diagram of System Control Circuit

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