参数资料
型号: THMC40DR
厂商: TEXAS INSTRUMENTS INC
元件分类: 运动控制电子
英文描述: BRUSHLESS DC MOTOR CONTROLLER, 1.5 A, PDSO14
封装: PLASTIC, SOP-14
文件页数: 19/19页
文件大小: 300K
代理商: THMC40DR
THMC40, THMC41
VARIABLE SPEED 12-VDC BRUSHLESS FAN MOTOR DRIVERS
SLIS097 – MARCH 2000
9
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
charge pump (CP)
THMC40 and THMC41 have an internal charge pump which utilizes an external reservoir capacitor (CP) to
generate the gate-drive voltage for the VOUT output high-side DMOS transistor (see Figure 3). The
recommended value for CP is 0.1
F, with a minimum rating of 35 WVdc. The charge pump is disabled during
the sleep state (see the sleep/run state section) to minimize current consumption into VPWR. The charge pump
also incorporates internal undervoltage lockout detection used to disable VOUT when the charge pump voltage
does not have an adequate level above VPWR to fully drive the high-side DMOS gate. Thus, the VCP (UVLO),
in conjunction with the charge pump start-up time, delays the VOUT drive for a short time after the device has
transitioned from sleep to run state, until the charge pump voltage reaches the UVLO threshold.
PWM oscillator/triangle waveform generator (COSC)
The PWM oscillator uses source and sink currents switched into an external capacitor (COSC) to set the PWM
frequency and generate a triangle waveform. A PWM oscillator cycle consists of charging COSC with a constant
current source (–180
A typical) until the COSC voltage ramps up to an upper threshold (2.3 V typical), and then
discharging COSC with a constant current sink (180 A typical) until the COSC voltage ramps down to a lower
threshold (0.5 V typical). The charge/discharge cycle is repeated each time the 2.3-V or 0.5-V threshold is
reached (see Figure 5).
V
2.3 V
S
R
Q
VREF
VPWR
COSC
VPWM
2200 pF
PWM
–180
A
2.3 V
0.5 V
180
A
Time
0.5 V
0
Q
VCOSC
Figure 5. PWM Triangle Waveform Generator
The following equation can be used to calculate the value of COSC needed for a desired PWM frequency, fPWM:
C
OSC(max) +
I
CHARGE(min)
2
f
PWM(min)
V
DISCHARGE *
V
CHARGE
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