SA56202 Datasheet, PDF (11/24 Pages) NXP Semiconductors – One-chip motor driver

Philips Semiconductors
SA56202
One-chip motor driver
where N_PP indicates the number of pole pairs of the motor. FG has an open-drain output
for easy interfacing to 3 V and 5 V logic.
7.7 Sled motor driver
Two current-steering PWM channels are available to drive a stepper motor. Per channel
an external sense resistor R_sense is used that is connected to ground. A peak-current
control loop is implemented that modulates the duty cycle of the PWM signal. See
Figure 9.
Rext _{VINSLD 47 kΩ}
47 kΩ
V_VINREF
input amplifier
+_Σ
−
R
Q
S
LOGIC
DRIVE
DRIVER
M
V_VINREF
CLOCK
70 kHz
A
IO
Rsense
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Fig 9. Peak-current control architecture of stepper motor driver.
The clock generator has a nominal frequency of f_osc/256 = 70 kHz. See Figure 10 for the
transfer function from input voltage V_VINSLD to output current at a typical R_sense of 0.5 Ω.
Input-to-output transconductance gain can be scaled down by connecting an external
resistor R_ext in series with the input VINSLD.
I_OUT (A)
1A
V_VINSLD − V_VINREF (V)
dead zone
−30 mV
+1 A/V
30 mV
−1 A
+1 A/V
001aaa436
Fig 10. Transfer function of stepper motor driver.
Both limit current and transconductance gain are related to R_sense in the following way:
Transconductance gain, _V--^I---^oi-_n- = ₂-----_×-----_R-¹---_s--_e--_n---_s--_e
9397 750 12772
Preliminary data sheet
Limit current, I_LIM = -₂----_×----¹-_R--^V--_s--_e--_n---_s--_e
Rev. 01 — 19 July 2004
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
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