NJM2644RB1-TE1 NJR, NJM2644RB1-TE1 Datasheet - Page 6

• Manufacturer Part Number: NJM2644RB1-TE1
• Description: Motor / Motion / Ignition Controllers & Drivers 2-Phase DC Brushless Motor Pre-driver IC
• Manufacturer: NJR

Specifications of NJM2644RB1-TE1

• Mounting Style: SMD/SMT
• Package / Case: TVSP-8
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

NJM2644
4. Design of Power Transistor base resistance (R4 and R5)
5. Design of spike killer for power transistor (ZD1 and ZD2)
- 6 -
can be obtained.
There are two methodologies to consume kick back voltage:
1) By insertion of ZD1 (zenner diode connected between Base and Emitter of TR1)
called as Echo noise) during operation.
Zenner diodes (often referred as spike killer ) are used for limiting kick back voltage of motor winding generated
when power transistors is (TR1 and TR2) turned off from on.
The optimum input voltage of NJM2644 is 100mVp-p and higher. With such input voltage, the highest efficiency
The output voltage of hall elements is influenced by the bias current and magnetic flux density of hall elements.
Given that the bias current is set to be 5mA by HW101A datasheet, R1 and R2 can be determined as follows:
HFE of 2SD2457 (Panasonic) is 80 from its datasheet. Given that Io is 300mA, the base current of TR1 is 3.75mA.
R4 is given by:
Where; VCC is 12V, VCE of NJM2644 is 1.5V, VBE of TR1 is 0.7V
A typical R5 value is ranging from 1k to 10k . As explained the above, it is highly recommended to determine
the value with actual application for better noise performance.
The pull down resistance R5 (connected to TR1) influences turn-off time of TR1.
Faster Turn-off time of TR1 reduces peak current of motor wining current resulting in lower echo fan noise (often
R
R
Energy of kick back voltage is consumed by TR1(or TR2). When ZD1 is in operation, Collector voltage is sum of
Vbe and ZD1. Therefore, breakdown voltage of ZD1 must be lower than that of TR1.
R
R
Motor Winding Current
4
4
1
1
VCC
12
R
R
. 3
2
2
75
0
7 .
1
Ihbias
VBE
10
Vcc
2 .
IB
k
1
3
5 .
VCE
5
. 2
61
12
10
10
3
3
2
4 .
2
6 .
k
k
Peak current becomes small early the turnoff the TR1