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參數(shù)資料
| 型號(hào)： | RT9002A |
| 廠商： | Richtek Technology Corporation |
| 英文描述： | Dual Low-Dropout Regulator with Detector |
| 中文描述： | 雙低壓差穩(wěn)壓器與探測(cè)器 |
| 文件頁(yè)數(shù)： | 10/11頁(yè) |
| 文件大小： | 210K |
| 代理商： | RT9002A |
RT9002A/B/C
10
DS9002ABC-03 March 2007
www.richtek.com
Applications Information
Like any low-dropout regulator, the external capacitors used
with the RT9002
A/B/C
must be carefully selected for
regulator stability and performance. Using a capacitor
whose value is > 1
μ
F on the RT9002
A/B/C
input and the
amount of capacitance can be increased without limit. The
input capacitor must be located a distance of not more
than 0.5 inch from the input pin of the IC and returned to a
clean analog ground. Any good quality ceramic can be
used for this capacitor. The capacitor with larger value and
lower ESR (equivalent series resistance) provides better
PSRR and line-transient response.
The output capacitor must meet both requirements for
minimum amount of capacitance and ESR in all LDOs
application. The RT9002
A/B/C
is designed specifically to
work with low ESR ceramic output capacitor in space-
saving and performance consideration. Using a ceramic
capacitor whose value is at least 1
μ
F with ESR is > 20m
Ω
on the RT9002
A/B/C
output ensures stability. The
RT9002
A/B/C
still works well with output capacitor of other
types due to the wide stable ESR range. Figure 1. shows
the curves of allowable ESR range as a function of load
current for various output capacitor values. Output capacitor
of larger capacitance can reduce noise and improve load
transient response, stability, and PSRR. The output
capacitor should be located not more than 0.5 inch from
the VOUT pin of the RT9002
A/B/C
and returned to a clean
analog ground.
Figure 1
Enable
The RT9002
A/B/C
goes into sleep mode when the Enable
pin is in a logic low condition. During this condition, the
pass transistor, error amplifier, and bandgap are turned off,
reducing the supply current to 0.1
μ
A typical. The Enable
pin may be directly tied to V
IN
to keep the part on. The
Enable input is CMOS logic and cannot be left floating.
PSRR
The power supply rejection ratio (PSRR) is defined as the
gain from the input to output divided by the gain from the
supply to the output. The PSRR is found to be
Note that when heavy load measuring,
Δ
supply will cause
Δ
temperature. And
Δ
temperature will cause
Δ
output
voltage. So the heavy load PSRR measuring is include
temperature effect.
Current Limit
The RT9002
A/B/C
contains an independent current limiter,
which monitors and controls the pass transistor's gate
voltage, limiting the output1/2 current to 0.45/0.8A (typ.).
The output can be shorted to ground indefinitely without
damaging the part.
Thermal-Shutdown Protection
Thermal-shutdown protection limits total power dissipation
in the RT9002
A/B/C
. When the junction temperature
exceeds T
J
= +170
°
C, the thermal sensor signals the
shutdown logic, turning off the pass transistor and allowing
the IC to cool. The thermal sensor turns the pass transistor
on again after the IC's junction temperature cools by 40
°
C,
resulting in a pulsed output during continuous thermal
overload conditions. Thermal-shutdown protection is
designed to protect the RT9002
A/B/C
in the event of fault
conditions. For continual operation, do not exceed the
absolute maximum junction temperature rating of T
J
=
+125
°
C.
Δ
Δ
×
=
Supply
Error
Gain
log
20
PSRR
Region of Stable C
OUT
ESR vs. Load Current
100
0.001
0.01
0.1
1
10
0
50
100
150
200
250
300
Load Current (mA)
R
)
RT9002APS
V
IN
= 4.0V, V
OUT2
= 3.3V
C
IN
= C
OUT
= 1uF/X7R
Unstable Region
Stable Region
Unstable Region (Simulation Verify)
O
Ω
)
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| RT9002A-GS | Dual Low-Dropout Regulator with Detector |
| RT9002A-PS | Dual Low-Dropout Regulator with Detector |
| RT9002B-GS | Dual Low-Dropout Regulator with Detector |
| RT9002B-PS | Dual Low-Dropout Regulator with Detector |
| RT9002C-GS | Dual Low-Dropout Regulator with Detector |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| RT9002A_11 | 制造商:RICHTEK 制造商全稱:Richtek Technology Corporation 功能描述:Dual Low Dropout Regulator with Detector |
| RT9002A-GS | 制造商:RICHTEK 制造商全稱:Richtek Technology Corporation 功能描述:Dual Low-Dropout Regulator with Detector |
| RT9002A-PS | 制造商:RICHTEK 制造商全稱:Richtek Technology Corporation 功能描述:Dual Low-Dropout Regulator with Detector |
| RT9002B-GS | 制造商:RICHTEK 制造商全稱:Richtek Technology Corporation 功能描述:Dual Low-Dropout Regulator with Detector |
| RT9002B-PS | 制造商:RICHTEK 制造商全稱:Richtek Technology Corporation 功能描述:Dual Low-Dropout Regulator with Detector |
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