LB1939T 查看數據表（PDF） - SANYO -> Panasonic
零件编号
产品描述 (功能)
生产厂家
LB1939T Datasheet PDF : 7 Pages
| |||
LB1939T
Constant Current Control Usage Notes
This IC supports both constant current control and constant voltage control modes. However, since both of these control
circuits operate at all times, certain of the limitations imposed by the constant voltage control circuit apply may when
using constant current control.
For example, if constant current control is used with the application circuit shown in figure 2, if VC = 0.9 V (= Vref) and
RFB = 1 Ω, then the output current can be calculated as follows from (1) on the previous page.
Iout = (0.9/4.5 + 0.03) / (1 + 0.1)
= 0.23/1.1
≈ 0.209A
Here, if the value driven load resistance RL is r, since the RFG pin voltage is 0.23 V and the npn transistor output
saturation voltage is 0.1 V (typical), the pnp transistor output pin voltage can be calculated as follows.
Vout = (RFG pin voltage) + (npn transistor output saturation voltage) + (voltage across the load terminals)
= 0.23 + 0.1 + 0.209 × r
= 0.3 + 0.209r
At the same time, however, this IC’s internal constant voltage control circuit controls the output voltage as follows.
Vout' = VC × 1.95 ≈ 1.75 V
Therefore, it will not be possible to use the constant current control mode if the value of r is set so that Vout is greater
than Vout'. That is, the condition
0.33 + 0.209r > 1.75
implies that
r > 6.79
This means that constant current control can be used when the value of the load resistance used is strictly less than 6.79 Ω.
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 or all SANYO products (including technical data, services) described or contained
herein are controlled under any of applicable local export control laws and regulations, such products must
not be exported without obtaining the export license from the authorities concerned 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 February, 2004. Specifications and information herein are subject
to change without notice.
PS No. 6194-7/7
Share Link: 