HI-SINCERITY

MICROELECTRONICS CORP.

Spec. No. : IC200401

Issued Date : 2004.02.01

Revised Date : 2005.07.14

Page No. : 4/8

H1117 Series

HSMC Product Specification

Applications Description

• Output Voltage Adjustment

Like most regulators, H1117 series regulate the output by

comparing the output voltage to an internally generated reference

voltage. On the adjustable version, the V

as 1.25V between V

and R

The output voltage is given by the following equation: V

(1+R

On fixed versions of H1117 series, the voltage divider is provided

internally.

• Thermal Protection

H1117 series have thermal protection which limits junction

temperature to 150

°C. However, device functionality is only

guaranteed to a maximum junction temperature of +125

°C.

The power dissipation and junction temperature for H1117 in all

packages given by

P

• Current Limit Protection

H1117 series are protected against overload conditions. Current protection is triggered at typically 1.5A.

• Stability And Load Regulation

H1117 series require a capacitor from V

compensation feedback to the internal gain stage. This is to

ensure stability at the output terminal. Typically, a 10uF tantalum

or 50uF aluminum electrolytic is sufficient.

Note : It is important that the ESR for this capacitor does not

exceed 0.5

Ω.

The output capacitor does not have a theoretical upper limit

and increasing its value will increase stability. C

more is typical for high current regulator design.

H1117 series load regulation are limited by the resistance of

the wire connecting it to the load(R

the best load regulation is accomplished when the top of the

resistor divider(R

H1117 series. When so connected, R

divider ratio. For fixed output versions, the top of R

connected to the output and ground pin can be connected to low

side of the load as a negative side sense if, so desired.

• Thermal Consideration

The H1117 series contain thermal limiting circuitry designed to protect itself for over-temperature conditions. Even for

normal load conditions, maximum junction temperature ratings must not be exceeded. As mention in thermal protection section,

we need to consider all sources of thermal resistance between junction and ambient. It contains junction-to-case, case-to-

heat-sink interface and heat sink resistance itself. An additional heat sink is applied externally sometimes. It can increase the

maximum power dissipation. For example, the equivalent junction temperature of 300mA output current is 115

°C without

external heat sink. Under the same junction temperature IC can operates 500mA with an adequate heat sink. Therefore, to

attach an extra heat sink is recommended.

Junction-to-case thermal resistance is specified from the IC junction to the bottom of the case directly below the die. The

bonding wires are appending paths. The former is the lowest resistance path. Proper mounting is required to ensure the best

possible thermal flow this area of the package to the heat sink. Thermal compound at the case-to-heat-sink interface is strongly

recommended. The case of all devices in this series is electrically connected to the output. Therefore, if the case of the device

must be electrically isolated, a thermally conductive spacer can be used, as long its thermal resistance is considered.

• Protection Diode

(The figure is shown as Regulator with Reverse Diode Protection in advanced applications)

In general operation, H1117 series don’t need any protection diodes. From the cross-section structure of H1117 sries, the

output pin is connected to P+ substrate, and the input pin is connected to N- well. There is a parasitic reverse diode between

them. It can handle microsecond surge currents of 5A to 10A. Even with large output capacitance, it is very difficult to get those

values of surge currents in normal operation. Only with high value output capacitors, such as 1000uF. And with the input pin

instantaneously shorted to ground. can damage occur. A crowbar circuit at the input of the H1117 series can generate those

kinds of currents, and a diode from output to input is recommended. Normal power supply cycling or even plugging and

unplugging in the system will not generate currents large enough to do any damage.

RL

R1

R2

Connect

R1 to Case

Connect

R2 to Load

Out

In

Adj

Parasitic

Line Resistance

V

R1

R2

In

Out

ADJ

10uA