RT9553A

®
RT9553A
High Accuracy Current/Voltage Sensing and Protection IC
General Description
Features
The RT9553A is designed for over-current detection and
over-/under-voltage protection.



It provides users to set over-current threshold by the ILIM
pin to compare that senses dropping voltage between CSP
pin and CSN pin. Moreover, users can set over-/undervoltage threshold by the OVSET pin/UVSET pin to
compare with the CSP voltage. The RT9553A is a available
in the WDFN-10L 3x3 package.





Common Mode Input Range up to 24V
VCC Operating Current : 200μ
μA
VCC Shutdown Current : 10μ
μA (under S3/S4/S5)
Programmable Over-Current Level
One Shot PROCHOT Signal when OCP
Pull Low RESET Signal when OVP/UVP
OVP/UVP with 8% Recover Hysteresis Range
Programmable OVP/UVP De-glitch Time
Applications
Ordering Information
RT9553A

Package Type
QW : WDFN-10L 3x3 (W-Type)
Notebook
Pin Configurations
Lead Plating System
G : Green (Halogen Free and Pb Free)
CSP
VCC
ILIM
EN
TIMER
Note :
Richtek products are :

RoHS compliant and compatible with the current require-
1
2
3
4
5
GND
(TOP VIEW)
11
10
9
8
7
6
CSN
PROCHOT
RESET
OVSET
UVSET
ments of IPC/JEDEC J-STD-020.

WDFN-10L 3x3
Suitable for use in SnPb or Pb-free soldering processes.
Marking Information
3U= : Product Code
3U=YM
DNN
YMDNN : Date Code
Simplified Application Circuit
RSENSE
Input
Output
ISENSE
RT9553A
Enable
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
DS9553A-00
September 2014
CSN
PROCHOT
CSP
RESET
VCC
OVSET
EN
UVSET
ILIM
TIMER
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1
RT9553A
Functional Pin Description
Pin No.
Pin Name
Pin Function
1
CSP
Positive Current Sense Input.
2
VCC
Power Supply Input. Connect this pin to 5V and place a minimum 0.1F
decoupling capacitor. The decoupling capacitor should be placed to this pin
as close as possible.
3
ILIM
Over-Current Trip Point Setting Input. The setting range is from 0.4V to 2V.
4
EN
Enable Control Input.
5
TIMER
Deglitch Time Setting of OV/UV Protection. Connect a resistor from this pin
tied to GND to set deglitch time. Do not parallel any filter capacitor to this pin.
6
UVSET
Under-Voltage Trip Point Setting Input. The setting range is from 0.55V to 3V.
7
OVSET
Over-Voltage Trip Point Setting Input. The setting range is from 0.55V to 3V.
8
RESET
Open-Drain Output. Connect to an external resistor to pull high. When OV/UV
occurs, this pin will be pulled low.
9
PROCHOT
Open-Drain Output. Connect to an external resistor to pull high. When OC
occurs, this pin will be pulled low.
10
CSN
Negative Current Sense Input.
11 (Exposed Pad)
GND
Ground. The exposed pad must be soldered to a large PCB and connected to
GND for maximum power dissipation.
Function Block Diagram
EN
VRON
VCC
Current Sensing
Amplifier
+
CSP
CSN
-
ILIM
POR
OC_Comparator
+
One Shot
-
PROCHOT
R1
OV_Comparator
-
OVSET
RESET
+
Deglitch
-
Latch
GND
+
UVSET
UV_Comparator
R2
TIMER
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is a registered trademark of Richtek Technology Corporation.
DS9553A-00
September 2014
RT9553A
Operation
The RT9553A consists of a current sensing amplifier, and
two comparators, and it provides the following functions :
over-current protection, over-voltage protection and undervoltage protection.
OVP/UVP Deglitch Time
Over-Current Protection
Over-/Under-Voltage Protection
With mΩ order of resistor shunts between CSP and CSN,
the current sensing amplifier multiplies the voltage between
CSP and CSN by 20 and compares the result with the
ILIM voltage. If the output voltage of current sensing
amplifier is larger than the ILIM voltage, the PROCHOT
voltage is pulled low.
The OVSET voltage is set by users and it compares with
the voltage which is 1/9 of CSP voltage with
OV_comparator. The UVSET voltage is set by users and
it also compares with the voltage which is 1/9 of CSP
voltage with UV_comparator. Either the output of
OV_comoparator or UV_comparator is high, the RESET
voltage is pulled low.
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
DS9553A-00
September 2014
The output signal of OV_comoparator or UV_comparator
is delayed by deglitch timer. The delayed time is decided
by the resistor (see spec.) connected to the TIMER pin.
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3
RT9553A
Absolute Maximum Ratings








(Note 1)
CSP/CSN to GND --------------------------------------------------------------------------------------------------------- −0.3V to 28V
VCC, ILIM, EN, UVSET, OVSET, RESET, PROCHOT to GND ------------------------------------------------- −0.3V to 6V
Power Dissipation, PD @ TA = 25°C
WDFN-10L 3x3 ------------------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2)
WDFN-10L 3x3, θJA ------------------------------------------------------------------------------------------------------WDFN-10L 3x3, θJC ------------------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------Junction Temperature ----------------------------------------------------------------------------------------------------Storage Temperature Range -------------------------------------------------------------------------------------------ESD Susceptibility (Note 3)
HBM (Human Body Model) ---------------------------------------------------------------------------------------------MM (Machine Model) -----------------------------------------------------------------------------------------------------
Recommended Operating Conditions




3.27W
30.5°C/W
7.5°C/W
260°C
150°C
−65°C to 150°C
2kV
200V
(Note 4)
High-Side Voltage, VCSP/VCSN -------------------------------------------------------------------------------------Supply Voltage, VCC ----------------------------------------------------------------------------------------------------Junction Temperature Range -------------------------------------------------------------------------------------------Ambient Temperature Range --------------------------------------------------------------------------------------------
5V to 24V
4.5V to 5.5V
−40°C to 125°C
−40°C to 85°C
Electrical Characteristics
(VCC = 5V, TA = 25°C, unless otherwise specified)
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
5
--
24
V
VCC = 5V, EN High
--
50
--
VCC = 5V, EN Low
--
--
5
CSN CSP Input
Input Voltage Range
VCSP, VCSN
ICSN + ICSP
A
VCC Input
VCC Operating Current
IVCC
--
200
--
A
VCC Shutdown Current
IVCC_shd
--
--
10
A
VCC POR Rising Voltage
VIN_POR
2.8
--
3.7
V
--
400
--
mV
Rising
Hysteresis
Enable
Enable Input
Voltage
Logic-High
VIH
0.7
--
--
Logic-Low
VIL
--
--
0.3
--
50
--
s
V
Over Current Protection
System Response Time
Open-Drain Output
Duration
TPROCHOT
10
--
18
ms
Open-Drain Output Ron
Ron_PROCHOT
--
--
10

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DS9553A-00
September 2014
RT9553A
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
Input Current Sensing
Accuracy
OCacc
VILIM = 0.4V to 2V
--
--
5
%
PROCHOT Leakage
Current
Ileak_PROCHOT
EN Low
--
--
5
A
ILIM Leakage Current
Ileak_ILIM
EN Low
--
--
5
A
ILIM Operation Range
VILIM
0.4
--
2
V
VOVSET = 0.55V to 3V
--
--
5
%
VOVSET = 0.55V to 3V
--
8
--
%
VUVSET = 0.55V to 3V
--
--
5
%
VUVSET = 0.55V to 3V
--
8
--
%
Over-/Under-Voltage Protection
OVP Accuracy
OVPacc
OVP Recover Hysteresis
Range
UVP Accuracy
UVPacc
UVP Recover Hysteresis
Range
Open Drain Output Ron
Ron_RESET
ISink = 10mA
--
--
10

RESET Leakage Current
Ileak_RESET
EN Low
--
--
5
A
OVP/UVP De-glitch Time
TTimer
RTimer = 375k
--
15
--
RTimer = 125k
--
5
--
s
Note 1. Stresses beyond those listed “Absolute Maximum Ratings” may cause permanent damage to the device. These are
stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in
the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions may
affect device reliability.
Note 2. θJA is measured at TA = 25°C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. θJC is
measured at the exposed pad of the package.
Note 3. Devices are ESD sensitive. Handling precaution is recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
DS9553A-00
September 2014
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RT9553A
Typical Application Circuit
ISENSE
Input
1.05V
Output
10m
RT9553A
10
100nF
CSN
PROCHOT
10k
9
100nF
1.05V
1 CSP
10k
100nF
2.2
2
5V
RESET
8
VCC
100nF
10k
3.3V
4
20k
5
3
2.2nF
EN
100nF
375k
63.4k
3.3V
37.4k
11 (Exposed Pad)
OVSET
TIMER
ILIM
82.5k
UVSET
6
82.5k
2.2nF
2.2nF
16.5k
GND
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DS9553A-00
September 2014
RT9553A
Typical Operating Characteristics
OVP Recovery Hysteresis
OVP Accuracy
8.0
OVP Recovery Hysteresis (%)
5
4
Accuracy (%)
3
2
1
0
-1
-2
-3
-4
7.9
7.8
7.7
7.6
7.5
7.4
7.3
VCC = 5V , OVSET = 0.4V to 3V
VCC = 5V , OVSET = 0.4V to 3V
7.2
-5
0.3
0.6
0.9
1.2
1.5
1.8
2.1
2.4
2.7
0.3
3
0.6
0.9
1.2
OVSET (V)
UVP Accuracy
1.8
2.1
2.4
2.7
3
2.7
3
UVP Recovery Hysteresis
8.0
UVP Recovery Hysteresis (%)1
5
4
3
Accuracy (%)
1.5
OVSET (V)
2
1
0
-1
-2
-3
-4
VCC = 5V , UVSET = 0.4V to 3V
-5
7.9
7.8
7.7
7.6
7.5
7.4
7.3
7.2
7.1
VCC = 5V , UVSET = 0.4V to 3V
7.0
0.3
0.6
0.9
1.2
1.5
1.8
2.1
2.4
2.7
3
0.3
0.6
0.9
1.2
1.5
1.8
2.1
2.4
UVSET (V)
UVSET (V)
OCP Accuracy
OVP vs. Reset Behavior
5
4
Accuracy (%)
3
2
RESET
(1V/Div)
VCSP
(7V/Div)
1
0
-1
-2
-3
OVSET
(1V/Div)
-4
VCC = 5V , RSENSE = 10mΩ , ILIM = 0.4V to 2V
VCC = 5V , OVSET = 2.6V , VCSP from 19V to 25V
-5
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
Time (50μs/Div)
ILIM (V)
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September 2014
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RT9553A
UVP vs. Reset Behavior
OCP vs. PROCHOT Behavior
VCSP
(2V/Div)
RESET
(2V/Div)
I LOAD
(2A/Div)
PROCHOT
(2V/Div)
UVSET
(500mV/Div)
ILIM
(1V/Div)
VCC = 5V , UVSET = 0.55V , VCSP from 7V to 3V
Time (10μs/Div)
VCC = 5V , ILIM = 1V , ILOAD = 0A to 6A
Time (20μs/Div)
Mask Time
I LOAD
(2A/Div)
PROCHOT
(2V/Div)
EN
(5V/Div)
VCC = 5V, RSENSE = 10mΩ,
ILIM = 1V, ILOAD = 0A to 6A before En high
Time (1ms/Div)
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is a registered trademark of Richtek Technology Corporation.
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September 2014
RT9553A
Application Information
The RT9553A provides OVP, UVP, OCP protection
functions with RESET, PROCHOT indicator to inform
system. It can be operated minimize external components
of switching power supply systems to achieve protection.
For easily using and increasing PCB space utilization,
the RT9553A is used in notebook applications.
Over-Voltage Protection (OVP)
The CSP pin voltage can be continuously monitored for
over-voltage condition.
When the CSP pin voltage exceeds the setting threshold
at the OVSET pin, the over-voltage protection will be
triggered, and the RESET pin will be pull low after a deglitch
time, the RESET is resumed when the CSP pin voltage
down to 8% hysteresis.
For more details, please refer to the following information.
The equation of over-voltage setting threshold is shown
as below :
R2
VOVSET  3.3V 
R1  R2
R2
VCSP  3.3V 
9
R1  R2
Under-Voltage Protection (UVP)
The principle of under-voltage protection is the same as
over-voltage protection function. The under-voltage
protection threshold is set by the UVSET pin.
When the CSP pin voltage is lower the setting threshold
at the UVSET pin, the under-voltage protection will be
triggered, and the RESET pin will be pull low after a deglitch
time, the RESET is resumed when the CSP pin voltage
up to 8% hysteresis.
Over-Current Protection (OCP)
As an industry standard, high accuracy current sense
amplifier is used to monitor the input current that flows
through current sense resistor. The RT9553A detects CSPCSN differential voltage across the current sense resistor
to monitor input current. The equation of over-current
protection is shown as below :
R6
R5  R6
(ISENSE  RSENSE )  20  VILIM
VILIM  3.3V 
ISENSE 
VILIM
20  RSENSE
We suggest that the total resistance of divider network
should be higher than 100kΩ.
We suggest that the total resistance of divider network
should be higher than 100kΩ.
VCSP is over-voltage protection trigger point.
ISENSE is over-current protection trigger point.
The 20 is amplification of internal error amplifier.
CSP
VCSP
ISENSE
3.3V
8R
OVSET
-
RSENSE
R1
+
R2
R3
-
UVSET
+
1R
TIMER
RTIMER
ILIM
R4
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September 2014
CSP
3.3V
R5
Fighre1.Setting Network of Over-Voltage Protection and
Under-Voltage Protection
DS9553A-00
CSN
3.3V
R6
Figure 2. Setting Network of Over-Current Protection
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RT9553A
RESET/Timer
PROCHOT
The RESET pin is an open-drain output, and requires to
be connected to a pull-up resistor. When over-voltage or
under-voltage occurs, the RESET pin will be pulled low
and resume to high with a hysteresis.
The PROCHOT pin is an open-drain output, and requires
to be connected to a pull-up resistor. When over-current
is detected, PROCHOT will be pulled low within 50μs for
15ms. If over-current condition keeps longer than 15ms,
PROCHOT maintains low status until over-current
protection is released.
Users can set the deglitch time of RESET by adjusting
the TIMER pin, and there are two choices of deglitch time,
15μs and 5μs. When the RTIMER is 375kΩ, the deglitch
time is 15μs; when the RTIMER is 125kΩ, the deglitch time
is 5μs. Users can choose a suitable deglitch time to avoid
protection false triggering.
Figure 3, Figure 4, Figure5 illustrates RESET and
PROCHOT indicator signals.
VCC
3ms
EN
ILIM
ISENSE
>15ms
PROCHOT
15ms
Figure 3. RESET and PROCHOT Indicator Illustration
VCC
EN
3ms
OVSET
Recovery Hysteresis Range
92%_OVSET
VCSP x (1/9)
RESET
Figure 4. OVP and RESET Indicator Illustrator
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September 2014
RT9553A
VCC
EN
3ms
VCSP x (1/9)
108%_UVSET
Recovery Hysteresis Range
UVSET
RESET
Figure 5. UVP and RESET Indicator Illustrator
Thermal Considerations
Maximum Power Dissipation (W)1
3.5
For continuous operation, do not exceed absolute
maximum junction temperature. The maximum power
dissipation depends on the thermal resistance of the IC
package, PCB layout, rate of surrounding airflow, and
difference between junction and ambient temperature. The
maximum power dissipation can be calculated by the
following formula :
PD(MAX) = (TJ(MAX) − TA) / θJA
where TJ(MAX) is the maximum junction temperature, TA is
the ambient temperature, and θJA is the junction to ambient
thermal resistance.
For recommended operating condition specifications, the
maximum junction temperature is 125°C. The junction to
ambient thermal resistance, θJA, is layout dependent. For
WDFN-10L 3x3 package, the thermal resistance, θJA, is
30.5°C/W on a standard JEDEC 51-7 four-layer thermal
test board. The maximum power dissipation at TA = 25°C
can be calculated by the following formula :
PD(MAX) = (125°C − 25°C) / (30.5°C/W) = 3.27W for
WDFN-10L 3x3 package
The maximum power dissipation depends on the operating
ambient temperature for fixed T J(MAX) and thermal
resistance, θJA. The derating curve in Figure 6 allows the
designer to see the effect of rising ambient temperature
on the maximum power dissipation.
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
DS9553A-00
September 2014
Four-Layer PCB
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0
25
50
75
100
125
Ambient Temperature (°C)
Figure 6. Derating Curve of Maximum Power Dissipation
Layout Considerations
Layout is very important in RT9553A, if designed
improperly, the PCB may radiate excessive noise. Certain
points must be considered before starting a layout for the
RT9553A.

Connect a RC low pass filter to VCC. The recommended
BOM of RC filter is 2.2Ω and 0.1μF. Place the filter
capacitor close to the IC.

Current sense connections must always be made using
Kelvin connections to ensure an accurate signal with
the current limit resistor located at the device.

All sensitive analog traces and components such as
CSP, CSN, VCC, EN, PROCHOT, RESET and ILIM
should be placed away form high voltage switching
nodes to avoid coupling.
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RT9553A
Outline Dimension
D2
D
L
E
E2
1
e
SEE DETAIL A
b
2
1
2
1
A
A1
A3
DETAIL A
Pin #1 ID and Tie Bar Mark Options
Note : The configuration of the Pin #1 identifier is optional,
but must be located within the zone indicated.
Symbol
Dimensions In Millimeters
Dimensions In Inches
Min
Max
Min
Max
A
0.700
0.800
0.028
0.031
A1
0.000
0.050
0.000
0.002
A3
0.175
0.250
0.007
0.010
b
0.180
0.300
0.007
0.012
D
2.950
3.050
0.116
0.120
D2
2.300
2.650
0.091
0.104
E
2.950
3.050
0.116
0.120
E2
1.500
1.750
0.059
0.069
e
L
0.500
0.350
0.020
0.450
0.014
0.018
W-Type 10L DFN 3x3 Package
Richtek Technology Corporation
14F, No. 8, Tai Yuen 1st Street, Chupei City
Hsinchu, Taiwan, R.O.C.
Tel: (8863)5526789
Richtek products are sold by description only. Richtek reserves the right to change the circuitry and/or specifications without notice at any time. Customers should
obtain the latest relevant information and data sheets before placing orders and should verify that such information is current and complete. Richtek cannot
assume responsibility for use of any circuitry other than circuitry entirely embodied in a Richtek product. Information furnished by Richtek is believed to be
accurate and reliable. However, no responsibility is assumed by Richtek or its subsidiaries for its use; nor for any infringements of patents or other rights of third
parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Richtek or its subsidiaries.
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DS9553A-00
September 2014