Voltage Regulator Example Ying Sun

Transcription

1 Voltage Regulator Example Ying Sun Voltage Regulator Circuit Vin is 9V. We want to regulate Vout at 5V. We use a zener diode of 3.3 V as shown in the attached data sheet. 1) Determine R1. R1 provides the bias current to keep the zener diode at the constant breakdown voltage VZ. According to the data sheet, for VZ = 3.3 V, the operating current IZT Should be 76 ma. Thus, R 1 = V in 3.3V 76 ma = 75Ω 2) If R2 is chosen to be 10 KΩ, what should R3 be? V Z = V out R 3 R 2 +R 3 R 3 = Thus, R3 should be set at 19.4 KΩ. R 2 V Z V out V Z = 10 K Ω 3.3V 5.0V 3.3V = 19.4 K Ω Page 1 of 2

2 Features: High reliability. Very sharp reverse characteristic. Low reverse current level. V z -tolerance ±5%. Applications: Voltage stabilization Absolute Maximum Ratings T j = 25 C Parameter Test Conditions Symbol Value Unit Power dissipation T amb 50 C P v 1 W Z-current - I z P v /V z ma Junction temperature - T j 200 Storage temperature range - T stg -65 to +175 C Maximum Thermal Resistance T j = 25 C Parameter Test Conditions Symbol Value Unit Junction ambient I = 9.5mm (3/8 inches) T L = constant R thja 100 K/W Stresses exceeding maximum ratings may damage the device. Maximum ratings are stress ratings only. Functional operation above the recommended operating conditions is not implied. Extended exposure to stresses above the recommended operating conditions may affect device reliability. Electrical Characteristics T j = 25 C Parameter Test Conditions Symbol Maximum Unit Forward voltage I F = 200mA V F 1.2 V Page <1> 06/04/11 V1.1

3 Specification Table Description V Znom 1) I ZT for r zit r zik at I ZK I R at V R Part Number V ma Ω Ω ma µa V Zener Diode N4728A < 10 < 100 Zener Diode < 400 1N4729A Zener Diode < 9 < N4730A Zener Diode < 8 < 500 1N4732A 1 Zener Diode < 7 < 550 1N4733A Zener Diode < 5 < N4734A Zener Diode < 2 3 1N4735A Zener Diode < 3.5 < N4736A Zener Diode < 4 5 1N4737A < 700 Zener Diode < N4738A Zener Diode < 5 7 1N4739A Zener Diode < N4740A 0.25 Zener Diode 62 4 < 125 < 2000 < N4759A 1) Based on DC-measurement at thermal equilibrium while maintaining the lead temperature (T L ) at 30 C, 9.5mm (3/8 inches) from the diode body. Characteristics (T j = 25 C unless otherwise specified) Symbol Parameter V Z I ZT Z ZT I ZK Z ZK I R V R I F V F Reverse zener voltage at I ZT Reverse current Maximum zener impedance at I ZT Reverse current Maximum zener impedance at I Zk Reverse leakage current at V R Breakdown voltage Forward current Forward voltage at I F Zener Voltage Regulator Page <2> 06/04/11 V1.1

4 Characteristics (T j = 25 C unless otherwise specified) Page <3> 06/04/11 V1.1

5 Standard Glass case JEDEC DO-41 Dimensions: Millimetres Marking Important Notice : This data sheet and its contents (the "Information") belong to the members of the Premier Farnell group of companies (the "Group") or are licensed to it. No licence is granted for the use of it other than for information purposes in connection with the products to which it relates. No licence of any intellectual property rights is granted. The Information is subject to change without notice and replaces all data sheets previously supplied. The Information supplied is believed to be accurate but the Group assumes no responsibility for its accuracy or completeness, any error in or omission from it or for any use made of it. Users of this data sheet should check for themselves the Information and the suitability of the products for their purpose and not make any assumptions based on information included or omitted. Liability for loss or damage resulting from any reliance on the Information or use of it (including liability resulting from negligence or where the Group was aware of the possibility of such loss or damage arising) is excluded. This will not operate to limit or restrict the Group's liability for death or personal injury resulting from its negligence. Multicomp is the registered trademark of the Group. Premier Farnell plc Page <5> 06/04/11 V1.1