
Data Sheet S17486EJ1V0DS
14
μ
PD168117A
7.6 Current Detection Resistor Connection (FB) Pin
(1) ch1 to ch4
The current detection resistor is connected when current driving is necessary. It is used for micro step driving and
solenoid driving.
The peak value (at 100% current of ch1 (ch3) or ch2 (ch4)) of output current is decided by the
resistance R
FB
linked to FB
1
(FB
3
) and FB
2
(FB
4
). This IC contains the reference power supply V
REF
for current value
comparison (500 mV TYP.) in the internal, and performs the drive which makes the current value acquired from R
FB
and V
REF
an output current peak value.
The current that flows into the output is {500 mV (reference voltage) /FB pin resistance x 1000}.
Peak output current: I
MAX
(A)
V
REF
(V) ÷ R
FB
(
) x 1000
Example)
Where FB = 4.7 k
Output current = 500 (mV) /4.7 (k
) x 1000
106.4 (mA)
This means constant current driving of about 106.4 mA.
When current driving is not performed, connect the FB pin to GND.
(2) ch7
Connect the current detection circuit between the source of the driver low side and GND. Because the circuit is
configured to detect current directly, connect a detection resistor of low resistance (1
maximum).
The current that flows into the output is {200 mV (reference voltage) /FB
7
pin resistance} (when SEL
7
= H).
Output current: I
MAX
(A)
V
REF
(V) ÷ R
FB
(
)
Example)
Where FB
7
= 0.5
Output current = 200 (mV) /0.5 (
)
= 400 (mA)
This means constant current driving of 400 mA.
Because only ch7 employs the linear drive mode and directly detects the output current, the current accuracy is
determined only by the external resistor and the offset of the current control amplifier.
The above example shows (SELV
REF7
= H) using the internal reference voltage. When applying reference
voltage externally, set SELV
REF7
to L, then apply voltage to the V
REF7
pin. The output current can be calculated
by transposing 200 mV in the computational expression.