H1084U Datasheet, PDF (3/5 Pages) Hi-Sincerity Mocroelectronics – 5A LOW DROPOUT POSITIVE VOLTAGE REGULATOR

HI-SINCERITY
MICROELECTRONICS CORP.
Spec. No. : Preliminary Data
Issued Date : 1998.06.01
Revised Date : 1999.08.01
Page No. : 3/5
Applications Description
• Output Voltage Adjustment
Like most regulators, the H1084U regulates the output
by comparing the output voltage to an internally generated
reference voltage. On the adjustable version, the V_REF is
V IN
available externally as 1.25V between V_OUT and ADJ. The
voltage ratio formed by R₁ and R₂ should be set to conduct
10mA (minimum output load). The output voltage is given
by the following equation : V_OUT =V_REF (1+R₂/R₁) + I_ADJ R₂
On fixed versions of H1084U, the voltage divider is
provided internally.
In
Out
ADJ
I _ADJ
10uA
V REF
V OUT
R1
R2
• Thermal Protection
H1084U has thermal protection which limits junction
temperature to 150°C. However, device functionality is
only guaranteed to a maximum junction temperature of
V_OUT =V_REF (1+R₂/R₁) + I_ADJ R₂
+125°C.
The power dissipation and junction temperature for H1084U in TO-263 package given by
P_D=(V_IN - V_OUT) I_OUT, T_JUNCTION=T_AMBIENT+(P_Dxθ_JA), Note : T_JUNCTION must not exceed 125°C
• Current Limit Protection
H1084U is protected against overload conditions. Current protection is triggered at typically 7.5A.
• Stability And Load Regulation
H1084U requires a capacitor from V_OUT to GND to
provide 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
R_P
Parasitic
Line Resistance
In
Out
V IN
Adj
not exceed 0.5Ω.
The output capacitor does not have a theoretical upper
R1
Connect
R1 to Case
RL
limit and increasing its value will increase stability. C_OUT =
R2
100 uF or more is typical for high current regulator design.
H1084U load regulation is limited by the resistance of
the wire connecting it to the load(R_P). For the adjustable
version, the best load regulation is accomplished when the
top of the resistor divider(R₁) is connected directly to the
Connect
R2 to Load
output pin of the H1084U. When so connected, R_P is not
multiplied by the divider ratio. For fixed output versions,
the top of R₁ is internally 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 H1084U 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 1A output current is 115°C without external heat sink. Under the same junction
temperature IC can operates 3A 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.
HSMC Product Specification