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Ordering number : EN4874
Thick Film Hybrid IC
STK6877
Reversible Brush-Type DC Motor Driver (output current: 8 A)
Overview
The STK6877 is an H bridge power pack reversible brushtype DC motor driver that uses Sanyo's unique insulated metal substrate technology (IMST) substrate. This technology provides superlative thermal dissipation characteristics. By adopting MOSFET devices as its power elements, this hybrid IC realizes reduced loss and increased current outputs as compared to our earlier STK6860H series.
* Wide operating power supply voltage range (VCC1 = 12 to 42 V) * Few required external components (Operation is possible with only two external bootstrap capacitors.)
Package Dimensions
unit: mm 4148
[STK6877]
Applications
* * * * Plain paper copier drum and scanner motors LBP drum motors Printer head carriage motors All types of DC motor application equipment
Features
* Increased margins with respect to rush currents due to the adoption of MOSFET elements * TTL level compatible inputs * Support for both two pin control saturation operation and three pin control PWM control * A braking function is provided.
Specifications
Absolute Maximum Ratings at Ta = 25C
Parameter Maximum supply voltage 1 Maximum supply voltage 2 Maximum motor rush current Operating substrate temperature Junction temperature Storage temperature range Symbol VCC1 max VCC2 max IO peak Tc max Tj max Tstg No signal No signal Period = 100 ms, duty 1% VCC2 = 5.0 V Conditions Ratings 50 7 18 105 150 -40 to +125 Unit V V A C C C
Any and all SANYO products described or contained herein do not have specifications that can handle applications that require extremely high levels of reliability, such as life-support systems, aircraft's control systems, or other applications whose failure can be reasonably expected to result in serious physical and/or material damage. Consult with your SANYO representative nearest you before using any SANYO products described or contained herein in such applications. SANYO assumes no responsibility for equipment failures that result from using products at values that exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or other parameters) listed in products specifications of any and all SANYO products described or contained herein.
SANYO Electric Co.,Ltd. Semiconductor Bussiness Headquarters
TOKYO OFFICE Tokyo Bldg., 1-10, 1 Chome, Ueno, Taito-ku, TOKYO, 110-8534 JAPAN
N2894TH (OT) No. 4874-1/8
STK6877
Specifications
Allowable Operating Ranges at Ta = 25C
Parameter Supply voltage 1 Supply voltage 2 Motor output current PWM frequency FET withstand voltage Symbol VCC1 VCC2 IOH max fp VDSS Input active Input active DC Conditions Ratings 12 to 42 5 5% 8 1 to 30 60 Unit V V A kHz V
Operating Characteristics at Ta = 25C, VCC1 = 24 V, VCC2 = 5.0 V
Parameter Quiescent current Output saturation voltage Input on voltage Input off voltage Input on current 1 Input on current 2 Input off current 1 Input off current 2 Diode forward voltage Sensing voltage Symbol ICCO Vst VIH VIL IIH1 IIH2 IIL1 IIL2 Vdf Vsens VI = 2.7 V, pin 14 VI = 2.7 V, pin 13 or pin 15 VI = 0.4 V, pin 14 VI = 0.4 V, pin 13 or pin 15 Idf = 8 A, VGS = 0 1.6 RL = 2.8 RL = 2.8 2.0 0 0.8 20 0.7 -0.4 -0.2 2.0 0.5 Conditions Ratings min 30 typ 40 0.90 max 50 1.20 Unit mA V V V A mA mA mA V V
Note: Constant voltage power supplies must be used.
Equivalent Circuit
Note: 1. Boot is an abbreviation for bootstrap. 2. The OSC pin (pin 11) must be left open in operation.
No. 4874-2/8
STK6877
Sample Application Circuit
A Forward Reverse Standby 1(illegal) Standby 2 H L H L
B L H H L
H: 5 V L: 0 V Note: 1. Input pin specifications * TTL levels handled * Maximum PWM input frequency: 30 kHz * When used in two pin control mode, the PWM pin must be tied high. 2. Since the OSC pin (pin 11) is a monitor pin, it should be left open in normal operation.
Thermal Design
1. Heat Sink Thermal Resistance (c-a) Derivation The size of the heat sink required for the hybrid IC is determined by the motor output current (IOH), the electrical characteristics of the motor and the chopping frequency, and the frequency of current application. The thermal resistance (c-a) of the heat sink is derived from the following formula. c-a = Tc max - Ta (C/W) Pd Tc max: Hybrid IC case temperature (C) Ta: Ambient temperature within the set (C) Pd: Average internal power dissipation within the hybrid IC (W) As an example, Figure 2 can be used to derive the required area for a 2 mm aluminum plate heat sink. Since the ambient temperature within a set varies greatly with the set internal air circulation conditions, the size of the heat sink must be determined taking into account the constraint that the temperature of the back surface of the IC (the aluminum plate side) must never under any conditions exceed 105C.
Figure 1 c-a vs. Pd
Figure 2 c-a vs. S
No. 4874-3/8
STK6877 2. Hybrid IC Internal Average Power Dissipation (Pd) Of the power dissipations within the hybrid IC, the following components have large power dissipations: the FETs that are the upper PWM elements in the H bridge structure, the lower FETs that form the motor direction reversing loop, and the flywheel FET body diode. This can be expressed as shown below from experiment (from the output current waveform in the figure below). Pd = upper FETs + lower FETs + body diode losses = Vst x IM x fp x tON + Vst x IM + Vdf x IM x fp x tOFF Vst: IM: Vdf: fp: FET saturation voltage (V) Motor output current (A) FET body diode forward voltage (V) Chopping frequency (Hz)
Figure 3 IM Waveform Model Figures 5 and 6 show the IO vs. Vst and IO vs. Vdf characteristics.
Figure 4 Model Circuit Diagram
Figure 5 IO vs. Vst 3. Junction Temperature, Tj The junction temperatures Tj (C) for each element (F1, F2, F3 and F4) can be derived from the formula below from the power dissipation Pds (W) for each element and the junction thermal resistances j-c (C/W). Tj = Tc + j-c x Pds (C) Pds: Loss per element Note that the thermal resistances for the power elements are as follows. F1, F2, F3, F4 j-c = 4 (C/W)
Figure 6 IO vs. Vdf
F1, F2, F3, F4, ASO Ta = 25C 1 pulse
No. 4874-4/8
STK6877
Usage Notes
1. Drive Circuit Start-up Procedure
Figure 7 Upper and Lower MOSFET Drive Circuits When starting (applying power to) the driver circuit (STK6877), the external control signals must be set to standby mode, i.e., pins A and B both set to low (setting both these pins high is an illegal mode). Then, after the specified power supply voltages (VCC1 and VCC2) have been input to the driver circuit, the circuit can be driven by inputting external control signals. 2. Illegal Input Mode with both the A and B Phase Signals (pins 13 and 15) High Since the circuit operation problems described below occur when the input signal mode with both signals high is used, this mode should be avoided. 2-1 If used in the standby state, the voltage (Vch) charged on the external bootstrap capacitor (47 F/16 V) will drop to an inadequate level. As a result, when the STK6877 driver circuit is switched to the start-up state, an insufficient drive voltage state for the upper FETs (F1 and F2) will occur. 2-2 If the A and B phase input signals are both switched to the high level in the motor start-up state (CW or CCW mode), a current loop (braking current) will be created in the upper side FETs due to the motor energy. At this point, since the upper FET drive voltage (the VGS voltage) drops, an insufficient drive state will occur in the upper FETs, and they may be destroyed. However, if during this operation the charge voltages Vch across the two terminals of the bootstrap capacitors (47 F/16 V) are monitored at the following points:
x y
The voltage between pin 10 and pin 8 (or 9) ......................................Phase A ...................(1) The voltage between pin 1 and pin 4 (or 5) ........................................Phase B
and if both these voltages can be maintained at 4.0 V or higher, then the A and B phase pin input signals can both set to high safely. In other words, if the A and B phase pin input signal mode with both signals high is used as a motor stopping technique, care must be taken to assure that the charge voltages Vch on the external bootstrap capacitors meet this condition. 3. Handling the Hybrid IC's PG (pins 2 and 3) and SG Pins (pin 12) Basically, the PCB pattern must be designed so that the PG and SG pins connect to a single grounding point. Also, if a current detection resistor (RE) is inserted on the PG pin, handle the PG and SG pins as shown in Figure 8, i.e., connect them to a single grounding point, and select a value of the resistor RE so that the voltage drop VRE meets the following condition. VRE = (IOH x RE) 0.5 V ...................................................(2) IOH: Motor output current (A) RE: Current detection resistance() VRE: Voltage drop across RE (V) The condition specified by formula (2) is specified in the specifications as the sensing voltage Vsens. Figure 8 Handling for the PG and SG Pins
No. 4874-5/8
STK6877 4. Braking Operation Procedures There are three methods for applying braking to the motor. (a) Setting both the A and B phase inputs to low. (This shorts the motor pins.) (b) Setting the PWM input low. (This effects motor flywheel current regenerative braking.) (c) After setting the PWM input low, setting both the A and B phase inputs to low. (This is the combination of methods (a) and (b).) (a) When braking method (a) is used, damping is applied through the lower MOSFETs. (This stops the motor quickly.) Since this method is equivalent to shorting the motor, the braking flywheel current rises radically, and the lower MOSFETs go to the overload state. As shown in Figure 9, F3 and F4 go to the overload state, and Figure 10 shows the flywheel current that flows in this braking method. Thus if this method is to be used, the user must confirm that, under the conditions of the actual application circuit, the flywheel current that flows in the lower FETs does not exceed the maximum rated current range for the hybrid IC. When brake method (b) is used, the motor drive current from before braking is applied is released in the lower MOSFETS thus resulting in a motor stopping operation. (This is a free running motor stop method.) Although the MOSFETs will not be overloaded, the braking is not as fast.
Note: (*) Braking applied during reverse motor rotation
Figure 9 Brake Method (a) Current Flow
Figure 10 Flywheel Current Flowing in the Lower FET (F4)
When brake method (c) is used, first the PWM input is set to low, and the motor's rotational energy is released to a certain degree. Then full braking is applied by setting both the A and B phase inputs to low. This method allows the flywheel current that flows in the lower MOSFETs to be held to within the maximum rated range by first applying method (b) braking, and then when the motor's rotational energy has been reduced, applying method (a) braking to stop the motor.
Note: (*) Braking applied during reverse motor rotation
Figure 11 Current Path in Brake Method (a)
No. 4874-6/8
STK6877 The dead time (td) and the flywheel current must be checked with the motor actually used, since the amount of dead time (td) that must be inserted between setting the PWM input low and setting the A and B phase inputs low to assure that the flywheel current is held within the maximum rated range will vary with the conditions under which the circuit operates. (See Figure 12.) Method (c) allows the motor to be stopped in a much shorter time than is possible with method (b). When releasing the brake it does not matter if the phase input signals or the PWM input signal is set high first.
Note: (*) Braking applied during reverse motor rotation
Although we have presented three braking methods, we recommend the use of method (c) due to the speed of braking and the current levels flowing during the braking operation. 5. Upper and Lower MOSFET Shorting Currents It is conceivable that both the upper and lower MOSFETs could be in the on state at the same time during braking operations (braking methods (a) and (c)) and release states. Taking this into consideration, the STK6877 provides two dead times (td1 and td2) of at least 1 s with respect to the input signals in the upper and lower MOSFET drive circuits as shown in the figure below. As a result there is no need for concern about shorting currents in the upper and lower MOSFETs.
Figure 12 Input Signal Timing Chart for Braking Method (c)
Figure 13 Upper and Lower MOSFET Equivalent Circuit
Note: td1: Dead time in the upper MOSFET drive circuit td2: Dead time in the lower MOSFET drive circuit (*) td1, td2 1 s
Figure 14 Upper and Lower MOSFET VGS Voltage Timing Chart
No. 4874-7/8
STK6877
Specifications of any and all SANYO products described or contained herein stipulate the performance, characteristics, and functions of the described products in the independent state, and are not guarantees of the performance, characteristics, and functions of the described products as mounted in the customer's products or equipment. To verify symptoms and states that cannot be evaluated in an independent device, the customer should always evaluate and test devices mounted in the customer's products or equipment. SANYO Electric Co., Ltd. strives to supply high-quality high-reliability products. However, any and all semiconductor products fail with some probability. It is possible that these probabilistic failures could give rise to accidents or events that could endanger human lives, that could give rise to smoke or fire, or that could cause damage to other property. When designing equipment, adopt safety measures so that these kinds of accidents or events cannot occur. Such measures include but are not limited to protective circuits and error prevention circuits for safe design, redundant design, and structural design. In the event that any and all SANYO products described or contained herein fall under strategic products (including services) controlled under the Foreign Exchange and Foreign Trade Control Law of Japan, such products must not be exported without obtaining export license from the Ministry of International Trade and Industry in accordance with the above law. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying and recording, or any information storage or retrieval system, or otherwise, without the prior written permission of SANYO Electric Co., Ltd. Any and all information described or contained herein are subject to change without notice due to product/technology improvement, etc. When designing equipment, refer to the "Delivery Specification" for the SANYO product that you intend to use. Information (including circuit diagrams and circuit parameters) herein is for example only; it is not guaranteed for volume production. SANYO believes information herein is accurate and reliable, but no guarantees are made or implied regarding its use or any infringements of intellectual property rights or other rights of third parties.
This catalog provides information as of August, 1998. Specifications and information herein are subject to change without notice. No. 4874-8/8

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