DATEL 78SR Service Manual

查询7803SR供应商

NEW

low-profi le package

Order online at www.datel.com

®

A SUBSIDIARY OF C&D TECHNOLOGIES

®

78SR Series

3.3V/5V/12V Outputs

High-Effi ciency Switching

Regulators with LM78XX Pinouts

Features

• 3.3V/0.5A, 5V/0.5A or 12V/0.4A outputs; Pin and size-compatible
with LM7805 & LM7812 regulators

• Up to 95% effi ciency – no heat sinks or thermal derating required!

• Two SIP-packages fi t existing TO-220 footprints:

Vertical-pin models occupy less than 0.1 square in.
Optional horizontal pins provide 0.350 in. installed height

• +7.5-36Vdc operating input range; Low 3mA quiescent current

• Built-in fi lter capacitors –no external components required

• –40 to +70°C operation at full load; Short-circuit protection

• Excellent load (±0.2%) and line (±0.3%) regulation

• Ideal for powering instrumentation from 9V/12V/24V/28V

supplies or batteries

• Can be used with unregulated dc supplies

Technical Notes

1. Input/Output (I/O) Filtering: As shown in the noise and ripple graphs,

78SR switching regulators exhibit excellent low-noise performance with

no external I/O capacitors. However, if additional noise reduction is

required, be sure to use low-ESR capacitors that are rated for continu-

ous operation (with an additional 20% safety margin) at the highest

system voltages and temperatures. Adding external output capacitors

will also improve the unit’s load-transient response.

Applications in which 78SR regulators are located more than 24

inches (61cm) from the input power supply should include an external

47uF/50V (or greater) aluminum electrolytic capacitor, connected as

close as possible to the regulator’s +Vin and GND terminals (pins 1

and 2). An external input capacitor is particularly important if the input

voltage is applied to the regulator via a mechanical switch or relay.

Contact bounce at turn-on can produce large inductive current-spikes,

and these current spikes can generate damaging voltage transients at

the regulator’s input terminals.

2. Input Fusing: 78SR switching regulators are not internally fused. If

fusing their input and/or output terminals is required, use the data

shown in the Effi ciency Curves as a guide to selecting an appropriate

slow-blow fuse.

3. Input-Output Isolation: 78SR regulators’ internal input and output

circuits share a common connection (GND, pin 2); there is no electrical

isolation between the INPUT (pin 1) and OUTPUT (pin 3) terminals.

DATEL’s 7805SR (5V output), 7812SR (12V output) and
7803SR (3.3V output) step-down switching regulators are
modern drop-in replacements for older, ineffi cient, LM7805 and
LM7812 linear regulators. The 78XXSR's are pin- and size­compatible with industry-standard TO-220 SIP packages. A
260kHz switching frequency provides for effi ciencies as high as
95%. Full-load (up to 0.5A) operation from 9V, 12V, 24V, or 36V
supplies at ambient temperatures up to +70°C requires no heat
sinks, no temperature derating, no forced-air cooling, and no
external capacitors.

78SR switching regulators provide many signifi cant
improvements over their linear counterparts: lower quiescent
current (3mA vs. 5 mA), higher input voltage (40V vs. 32V),
and better output accuracy (±1.5% vs. ±5%). All these features
combine to make 78SR regulators ideal for new or existing
LM7805 & LM7812 applications requiring full-load operation at
elevated voltages.

4. Overvoltage Protection: 78SR switching regulators do not provide

input or output overvoltage protection. In the extremely rare situation

in which a catastrophic failure occurs, the output voltage may rise

to excessively high levels. If your load must be protected against

all possible overvoltage situations, external voltage-limiting circuitry

must be provided.

5. Operation at 40Vdc: Operating with inputs up to 40Vdc is permissible

if, for inputs between 36 and 40Vdc, the maximum load current is

reduced to 0.35A for 7805SR and 7803SR, and to 0.3A for 7812SR.

Under no circumstances should the input voltage be allowed to

exceed 45Vdc.

6. Soldering & Handling Precautions: All units are designed to be

hand soldered to pc-boards using no-clean solders (+260°C, 5 sec-

onds max.). Water-soluble solders can also be used, but the units

must be washed and dried using processes appropriate to the type of

solder employed. See the Mechanical Specifi cations section for pin 1

orientation and recommended plated-through hole dimensions.

While 78SR regulators easily withstand a 2kV ESD discharge to any

terminal (using human body model), they should always be treated as

ESD sensitive devices.

7. Horizontal-Pin Models (78XXSRH): 78XXSRH switching regulators

are pin-compatible replacements for TO-220 style LM78XX linear reg-

ulators that are installed with their metal tabs lying fl at on the surface

DATEL, Inc., Mansfi eld, MA 02048 (USA) • Tel: [phone] Fax: [phone] • E–mail: [e-mail] • Internet: www.datel.com

78SR Series

HIGH-EFFICIENCY SWITCHING REGULATORS

Technical Notes (continued)

of the pc-board. However, because the surface of inductor L1 on

78XXSRH models is electrically conductive, it must not be allowed to

come in contact with any exposed pc-board traces, other than power

ground (GND).

While the 2-mil-thick (0.05mm) polyester label attached to L1 provides

some degree of electrical insulation (only if L1 sits perfectly fl at on

the pc-board), it is recommended that a 0.020” (0.5mm) clearance be

maintained between L1 and all exposed pc-board traces.

8. Dropout Voltage: 78SR series regulators described in this data sheet

specify a minimum input voltage at which full-load accuracy and output

regulation are guaranteed (7.5V for 7803SR and 7805SR, and 15.0V

for 7812SR). However, these devices will stay in regulation at lower

input voltages if they are operated at less than their rated loads.

The following dropout-voltage data, derived from sample testing per-

formed at an ambient temperature of +25°C with resistive loads, should

be used for information purposes only. For these tests, a unit was

considered to be out of regulation when its output changed by more

+/-0.005Vdc from its nominal value. All voltages were measured directly

at the regulator’s I/O pins.

Typical Dropout Voltage

0% Load 25% Load 50% Load 100% Load

7803SR 6.0V 6.2V 6.2V 6.3V

7805SR 6.3V 6.2V 6.2V 6.8V

7812SR 12.8V 13.0V 12.8V 13.0V

Performance/Functional Specifi cations

Typical at TA = +25°C

Input/Output

Models 7803SR 7805SR 7812SR

Output Voltage +3.3Vdc +5.0Vdc +12.0Vdc

Rated Output Current 0.5A 0.5A 0.4A

Output Voltage Accuracy ±2% ±1.5% ±2%

Input Voltage Range ➀ +7.5-36Vdc +7.5-36Vdc +15-36Vdc

Line Regulation (100% load) ±0.3% ±0.3% ±0.3%

Load Regulation (0-100% load) ±0.2% ±0.2% ±0.2%

Quiescent Current 3mA typ., 5mA max.

Input Current See Performance Curves

Effi ciency See Performance Curves

Transient Response See Performance Curves

Input & Output Noise See Performance Curves

Short Circuit Protection ➁ Continuous

Isolation None

Overvoltage Protection None

Undervoltage Protection None

Environmental

Models 7803SR 7805SR 7812SR

Operating Temperature –40 to +70°C

Storage Temperature –40 to +85°C

Cooling Free Air Convection

Humidity (Non-condensing) 0 to 85%

Physical

Mechanical See Mechanical Specifi cations

Packag e Open-frame SIP

Pins 0.025” (0.64mm) square,

tin-plated bronze

Weight 0.08 ounces (2.2g)

Pin Soldering +260°C for 5 seconds

➀ See Technical Note 5.

➁ While these regulators can withstand a continuous short-circuit across their

output terminals, they will experience a signifi cant temperature rise. Extended
short-circuit operation will adversely affect the unit’s reliability.

Ordering Information

DATEL Part No. Output Voltage Output Current Input Voltage

Standard Pin Package
7803SR +3.3Vdc 0.5A +7.5-36Vdc
7805SR +5.0Vdc 0.5A +7.5-36Vdc
7812SR +12.0Vdc 0.4A +15-36Vdc

Horizontal Pin Package
7803SRH +3.3Vdc 0.5A +7.5-36Vdc
7805SRH +5.0Vdc 0.5A +7.5-36Vdc
7812SRH +12.0Vdc 0.4A +15-36Vdc

DATEL, Inc., Mansfi eld, MA 02048 (USA) • Tel: [phone] Fax: [phone] • E–mail: [e-mail] • Internet: www.datel.com

2