LB1975(2003) データシートの表示（PDF） - SANYO -> Panasonic
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LB1975 Datasheet PDF : 10 Pages
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LB1975
Hall Input Circuit
The Hall input circuit is a differential amplifier with a hysteresis of 32 mV (typ.). The operation DC level must be within
the common-mode input voltage range (1.5V to VCC – 1.5 V). To prevent noise and other adverse influences, the input
level should be at least 3 times the hysteresis (120 to 160 mVp-p). If noise at the Hall input is a problem, a noise-
canceling capacitor (about 0.01 µF) should be connected across the Hall input IN+ and IN– pins.
FG Output Circuit
The Hall input signal at IN1, IN2, and IN3 is combined and subject to waveform shaping before being output. The signal
at FG1 has the same frequency as the FG1 Hall input, and the signal at FG2 has a frequency that is three times higher.
Start/Stop Control Circuit
The start/stop control circuit turns the source-side output transistors OFF (motor stop) when a High signal is input at the
S/S pin or when the pin is Open. When a Low signal is input at the S/S pin, the source-side output transistors are turned
ON, and the normal operation state is established (motor start).
Forward/Reverse Switching
This IC is designed under the assumption that forward/reverse switching is not carried out while the motor is running. If
switching is carried out while the motor is running, reverse torque braking occurs, leading to a high current flow. If the
current limiter is triggered, the source-side output transistors are switched off, and the sink-side output transistors go into
the short brake condition. However, because the current limiter of this IC cannot control the current flowing in the sink-
side output transistors, these may be destroyed by the short brake current. Therefore F/R switching while the motor is
running is permissible only if the output current (IO) is limited to a maximum of 2.5 A using the motor coil resistance or
other suitable means.
F/R switching should be carried out only while a High signal is input to the S/S pin or the pin is Open (stop condition), or
while the VCTL pin conforms to the following condition: VCTL ≤ VCTL1 (duty cycle 0%). In any other condition, F/R
switching will result in feedthrough current. The F/R pin should therefore be fixed to Low (forward) or High or Open
(reverse) during use.
VCC, VM Power Supplies
When the power supply voltage (VCC, VM) rises very quickly when a power is first applied, a feedthrough current may
occur at the output. If the current remains below about 0.2 A to 0.3 A, it does not pose a problem, but such a possibility
should still be prevented by slowing down the voltage rise at power-on. Especially if the F/R pin is set to High or Open
(reverse), a quick rise in VCC is likely to cause feedthrough current. This should be prevented by ensuring that ∆VCC / ∆t
= 0.2 V/µs or less. Feedthrough current can also be prevented by first switching on VCC and then VM during power-on.
The sequence at power-down should be as follows. Provide a stop input to the S/S pin or a duty ratio 0% input to the
VCTL pin. When the motor has come to a full stop, switch off VM and then VCC. If power is switched off while the
motor is still rotating or a current is flowing in the motor coil (including motor restraint or inertia rotation), a
counterelectromotive current or kickback current may flow on the VM side, depending on the motor type and power-off
procedure. If this current cannot be absorbed by the VM power supply or a capacitor, VM voltage may rise and exceed
the absolute maximum VM rating for the IC. Ensure that this does not happen through proper design of the VM power
supply or through use of a capacitor.
Because the IC (LB1975) incorporates a shunt regulator, it can be used on a single power supply. In this case, supply
VCC (6.3 typ.) to the VREG pin via an external NPN transistor and resistor. When not using the regulator, leave the VREG
pin open.
No. 6087-10/12
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