AAT4685
Over-Voltage Protection Switch with OCP and BOVPOVPSwitchTM
PRODUCT DATASHEET
4685.2009.03.1.0 1
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General Description
The AAT4685 OVPSwitch™ is a member of AnalogicTech’s
Application Specific Power MOSFET™ (ASPM™) product
family. It is an N-channel MOSFET power switch with
precise over-voltage protection control, designed to pro-
tect low-voltage systems against high-voltage faults up
to +28V. It also integrates over-current protection
(OCP), battery over-voltage protection (BOVP) and over-
temperature protection (OTP).
When the input voltage exceeds the programmed over-
voltage threshold, the N-channel MOSFET switch will be
turned off to prevent damage to the output load circuits.
An external resistor divider is adopted to program the
adjustable version over-voltage trip point. Over-current
protection protects the case of output short circuits by
disconnecting the load from the input supply.
A battery voltage monitor is integrated and disconnect
the IN and OUT when the battery voltage exceed its rated
voltage. The AAT4685 also monitors its own die tempera-
ture and OVP switch off if it becomes too hot.
The AAT4685 includes an under-voltage lockout (UVLO)
protection circuit, which puts the device into sleep mode
at low input voltages only consuming 100A current. It
also includes two indicators: input supply power good
indicator (POK) which is always active whether EN is low
or high, and a fault flag indicator (FLT) which goes to
active low when a fault condition (OV, OC, BOV and OT)
occurs at EN = low.
The AAT4685 is offered in a Pb-free, 3x3mm 12-pin
TDFN package with a pin-out optimized for safety and is
specified for operation over the -40°C to +85°C ambient
temperature range.
Features
• V
IN Range: 3.0V – 28V
• OVP Threshold Setting Range: 4V – 7V
Fixed: 5.85V and 6.8V
Adjustable
• Fast OVP Response:
1s (max) Response to Over-Voltage Transient
• OVP Recovery Delay Time: 8ms
• Over-Current Protection
• Adjustable 0.3 – 1.8A
• Battery OVP 4.35V
• Thermal Shutdown Protection
• Low Quiescent Current
600A Typical
100A Typical Standby Current
• Under-Voltage Lockout
• 120m Typical RDS(ON) at 5.0V
• Active Low Enable with Internal 200k Pull-Down
Resistor
• Input Supply Power Good Indicator, Open Drain
• OVP/OCP/BOVP/OT Fault Indicator, Open Drain
• Temperature Range: -40°C to 85°C
• 3x3mm TDFN-12 Package
Applications
• Cell Phones
• Digital Still Cameras
• MP3
• Personal Data Assistants (PDAs)
Typical Application
C1
1μF
C2
1μF
IN
OVP
FLT
EN
OUT
GND
VIN 3.0V – 28V
VOUT
Fault Flag
OCP BOVP
POK
VIO VIO
IC
AAT4685
ROVP1
ROVP2 ROCP
BAT
AAT4685
Over-Voltage Protection Switch with OCP and BOVPOVPSwitchTM
PRODUCT DATASHEET
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Pin Descriptions
Pin # Symbol Function
1 OCP Over-current protection threshold input. Connect resistor to ground to set OCP limit.
2 IC Internally connected. Connect this pin to ground.
3EN Active low enable with internal 200k resistor pull down to GND
4POK Input supply power-good status pin, open-drain. The POK function is always active whether EN is low or
high. Connect a 1k to 100k pull-up resistor to the logic I/O voltage of the host system.
5,6 OUT Output. Connect a 0.1F~47uF capacitor from OUT to GND.
7,8 IN Power input pin. Connect 1F capacitor from IN to GND.
9 GND Ground connection.
10 FLT
Open-drain output. Active low when input over-voltage, input over-current, battery over-voltage, or over
temperature and EN = low. The FLT pin goes to high impedance state when EN = high. Connect a 1k to
100k pull-up resistor to the logic I/O voltage of the host system.
11 BOVP Battery voltage sense input. Connect to battery positive terminal through a 100k resistor to limit the
current in case of a short circuit condition.
12 OVP (N/C) Over-voltage protection threshold input (Adjustable only). Fixed version not connected.
Pin Configuration
TDFN33-12
(Top View)
OCP
IC
EN
1
POK
OUT
OUT
OVP (N/C)
BOVP
FLT
GND
IN
IN
2
3
4
5
6
12
11
10
9
8
7
AAT4685
Over-Voltage Protection Switch with OCP and BOVPOVPSwitchTM
PRODUCT DATASHEET
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1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at conditions other than the operating conditions
specified is not implied. Only one Absolute Maximum Rating should be applied at any one time.
2. Mounted on a FR4 board.
3. Derate 25mW/°C above 25°C.
Absolute Maximum Ratings1
Symbol Description Value Units
VIN IN to GND -0.3 to 28 V
VNBOVP, OVP , OCP, OUT , IC to GND -0.3 to VP +0.3 V
VPFLT, EN, POK to GND -0.3 to 7.5 V
IMAX Maximum Continuous Switch Current 1.9 A
TJOperating Junction Temperature Range -40 to 150 °C
TSStorage Temperature Range -65 to 150 °C
TLEAD Maximum Soldering Temperature (at leads, 10 sec) 300 °C
Thermal Characteristics
Symbol Description Value Units
ΘJA Maximum Thermal Resistance2 50 °C/W
PDMaximum Power Dissipation2, 3 2W
AAT4685
Over-Voltage Protection Switch with OCP and BOVPOVPSwitchTM
PRODUCT DATASHEET
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1. The AAT4685 is guaranteed to meet performance specification over the -40 to 85°C operating temperature range and are assured by design, characterization and correlation
with statistical process controls.
Electrical Characteristics1
VIN = 5V, VBOVP = 4.2V, V/EN = 0V , ROCP = 30kΩ , TA = -40°C to 85°C unless otherwise noted. Typical values are at TA
= 25°C.
Symbol Description Conditions Min Typ Max Units
VIN Input Voltage Range 3 28 V
IQOperation Quiescent Current IOUT = 0, ROCP = 30k600 800 A
ISTDBY
Standby Current (Only UVLO and OVP
circuit is “Enable”, other function blocks
are all “Disable”)
EN = 5V, VOUT = 0 100 150 A
VUVLO Under-Voltage Lockout Threshold Rising edge 2.5 2.7 2.9 V
VUVLO_HYS Under-Voltage Lockout Hysteresis 0.1 V
TDGL Deglitch Time, Input Power Detected
Status
Time measured from VIN 0V to 5V;
1s rise time to Output Turn ON 8ms
Input OVP – Adjustable (AAT4685-1) ( Measured at OVP pin )
VOVP_TH Over-Voltage Lockout Threshold Rising Edge 0.97 1.0 1.03 V
VOVP_HYS
Over-Voltage Lockout Threshold
Hysteresis 20 mV
VOVP_RANGE
Over-Voltage Lockout Threshold
Adjustable Range 47V
TRESP_OV Over-Voltage Response Time VOVP rise to 1.13V from 1.07V in 1ns 1.0 s
TOVP_REC
Recovery Time From Input Over-Voltage
Release VOVP fall to 1.07V from 1.13V in 1ns 8 ms
Input OVP – Fixed (AAT4685-2 and AAT4685-3) ( Measured at IN pin )
VOVPT
Overvoltage Protection
Trip Voltage
AAT4685-2 Rising Edge 6.60 6.80 7.0 V
AAT4685-3 5.71 5.85 6.0 V
VOVP_HYS
Over-Voltage Protection Trip Point
Hysteresis 60 mV
TRESP_OV Over-Voltage Response Time VIN rise to 7.5V from 5V 1.0 s
TOVP_REC
Recovery Time From Input Over-Voltage
Release VIN fall to 5V from 7.5V 8 ms
Input OCP
IOCP Over-Current Range (Programmable) 0.3 1.8 A
ΔIOCP/IOCP Over-Current Trip Tolerance Rising Edge. ROCP = 30kΩ0.9 1.0 1.1 A
TOCP_BL
Blanking Time, Input Over-Current
Detected 180 s
TOCP_REC
Recovery Time From Input Over-Current
Condition 64 ms
Battery OVP ( Measured at BOVP pin )
VBOVPT
Battery Over-Voltage Protection Trip
Voltage Rising Edge 4.2 4.35 4.5 V
VBOVP_HYS
Battery Over-Voltage Protection Trip
Point Hysteresis 275 mV
IBOVP Battery OVP Pin Input Current 100 nA
TBOVP_BL Battery OVP Pin Blanking Time 180 s
AAT4685
Over-Voltage Protection Switch with OCP and BOVPOVPSwitchTM
PRODUCT DATASHEET
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1. The AAT4685 is guaranteed to meet performance specification over the -40 to 85°C operating temperature range and are assured by design, characterization and correlation
with statistical process controls.
Electrical Characteristics1
VIN = 5V, VBOVP = 4.2V, V/EN = 0V , ROCP = 30kΩ , TA = -40°C to 85°C unless otherwise noted. Typical values are at TA
= 25°C.
Symbol Description Conditions Min Typ Max Units
OVP Switch
RDS(ON) On-Resistance ROCP = 16.5kΩ, IOUT = 1200mA 120 200 mΩ
ID(OFF) Switch Off-Leakage EN = 5V 1 A
Logic Control and Protection
VEN(L) EN Input Low Voltage 0.4 V
VEN(H) EN Input High Voltage 1.2 V
IEN(H) EN Input Current VEN = 5.0V, Internal Pulldown = 200k 25 A
VFLT FLT Output Low Voltage IFLT = 4mA 0.4 V
IFLT FLT Output Leakage VIN = 0V, FLT = 5.5V 1 A
VPOK POK Output Low Voltage IPOK = 4mA 0.4 V
IPOK POK Output Leakage VIN = 0V, POK = 5.5V 1 A
TON OVP Switch Turn On Delay Time EN from 0V to 5V; ROUT = 10Ω; COUT= 1F8 ms
TSHDN Chip Thermal Shutdown Temperature Threshold 140 ºC
Hysteresis 15
AAT4685
Over-Voltage Protection Switch with OCP and BOVPOVPSwitchTM
PRODUCT DATASHEET
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Typical Characteristics
Operation Quiescent Current vs. Temperature
Temperature (°C)
IQ (μA)
-40 -15 10 35 60 85
580
590
600
610
620
Standby Current vs. Temperature
Temperature (°C)
ISB (μA)
-40 -15 10 35 60 85
85
90
95
100
105
110
Operation Quiescent and Standby Current
vs. Supply Voltage
Supply Voltage (V)
Current (μA)
3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5
0
100
200
300
400
500
600
700
IQ
ISB
Under-Voltage Lockout Threshold
vs. Temperature
Temperature (°C)
UVLO Threshold (V)
-40 -15 10 35 60 85
2.55
2.60
2.65
2.70
2.75
2.80
UVLO_Hi
UVLO_Lo
AAT4685-1 Input OVP Threshold
vs. Temperature
Temperature (°C)
OVP Threshold (V)
-40 -15 10 35 60 85
0.97
0.98
0.99
1.00
1.01
OVP_Rising
OVP_Falling
Battery Over-Voltage Protection Trip Voltage
vs. Temperature
(VIN = 5.0V)
Temperature (°C)
VBOVPT (V)
-40 -15 10 35 60 85
4.00
4.05
4.10
4.15
4.20
4.25
4.30
4.35
4.40
4.45
4.50
Battery OVP_Thresh_hi
Battery OVP_Thresh_low
AAT4685
Over-Voltage Protection Switch with OCP and BOVPOVPSwitchTM
PRODUCT DATASHEET
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Typical Characteristics
EN VIH and VIL vs. Supply Voltage
Supply Voltage (V)
VEN (V)
3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0
0.60
0.65
0.70
0.75
0.80
0.85
0.90 VIH
VIL
EN Pin vs. Temperature
(VIN = 5.0V)
Temperature (°C)
VEN (V)
-40 -15 10 35 60 85
0.60
0.65
0.70
0.75
0.80
0.85
0.90
VIH
VIL
Over-Current Limit vs. ROCP
ROCP (kΩ)
IOCP (A)
0.00
0.25
0.50
0.75
1.00
1.25
1.50
1.75
2.00
2.25
10 100
NMOS On-Resistance vs. Temperature
Temperature (°C)
RDS(ON) (mΩ)
-40 -15 10 35 60 85
95
110
125
140
155
Normal Power-On Startup
(ROUT = 6.3Ω)
Time (2ms/div)
VIN
(2V/div)
IOUT
(500mA/div)
VOUT
(2V/div)
Over-Current Protection
(IOUT switches from 0.8A to 1.5A, ILIM = 1A)
Time (50μs/div)
VIN
(5V/div)
IOUT
(500mA/div)
FLT
(5V/div)
VOUT
(2V/div)
5V
AAT4685
Over-Voltage Protection Switch with OCP and BOVPOVPSwitchTM
PRODUCT DATASHEET
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Typical Characteristics
Over-Voltage Protection Response
for Input Step
(VIN = 5V to 12V)
Time (20μs/div)
VIN
(2V/div)
FLT
(5V/div)
VOUT
(2V/div)
Recovery from Over-Voltage Protection
(VIN = 7V to 5V)
Time (2ms/div)
VIN
(2V/div)
IOUT
(500mA/div)
FLT
(5V/div)
VOUT
(2V/div)
Battery Over-Voltage Protection
(VBOVP steps from 3.8V to 4.5V)
Time (100μs/div)
VBOVP
(1V/div)
IOUT
(500mA/div)
FLT
(5V/div)
VOUT
(2V/div)
Recovery from Battery Over-Voltage Protection
(VBOVP = 4.5V to 3.8V)
Time (500μs/div)
VBOVP
(1V/div)
IOUT
(500mA/div)
FLT
(5V/div)
VOUT
(2V/div)
Battery Over-Voltage Protection
(VBOVP Cycles Between 4V and 4.5V)
Time (20ms/div)
VBOVP
(2V/div)
FLT
(5V/div)
VOUT
(2V/div)
Power-up into Short Circuit
on the OUT Pin
Time (200ms/div)
VIN
(5V/div)
VOUT
(5V/div)
FLT
(5V/div)
IOUT
(500mA/div)
AAT4685
Over-Voltage Protection Switch with OCP and BOVPOVPSwitchTM
PRODUCT DATASHEET
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Functional Block Diagram
OCP
UVLO
Driver
Control
and Timer
Bias
and BG
INT
Regulator
FLT
OUT
BOVP
GND
OVP
IN
OCP
EN
INT_V P
INT_V P INT_V P
INT_V P
OTP
option
CP
POR
POK
Detect
POK
OVP
Switch
VREF
VREF
VREF
Functional Description
The AAT4685 provides up to 28V over-voltage and over-
current protection when powering low-voltage systems
such as cell phones, MP3, and PDAs or when charging
Lithium Ion batteries from a badly regulated supply. The
AAT4685 is inserted between the power supply or char-
ger source and the load to be protected. The AAT4685 IC
consists of a low resistance OVP switch, under-voltage
lockout protection, over-voltage monitor and protection,
over-current protection, battery over-voltage protection,
fast shut-down circuitry and a fault output flag.
In normal operation the OVP switch acts as a slew-rate
controlled load switch, connecting and disconnecting the
power supply from IN to OUT. A low resistance N chan-
nel MOSFET is used as to minimize the voltage drop
between the voltage source and the load and to reduce
the power dissipation.
When the voltage on the input exceeds the programmed
over-voltage trip point, the device immediately turns off
the internal OVP switch disconnecting the load from the
abnormal voltage, preventing damage to any down-
stream components. In the case of an over current con-
dition, it limits the system current at the threshold value,
and if the over current persists, the OVP switch is turned
off after a blanking period. If the battery voltage rises to
an unsafe level (BOVP threshold), the IC disconnects
OUT from the charging input power IN until the battery
voltage returns to an acceptable value. BOVP or OCP
blanking time ignores short time transients of over-bat-
tery voltage and overload current. Additionally, AAT4685
also monitors its own die temperature and turns the OVP
switch off if it becomes too hot.
The AAT4685 has a fault flag (FLT) pin to indicate the
fault conditions of input power over-voltage, load current
over-current, battery over-voltage, and over-tempera-
ture by pulling the flag signal down to alert the system.
If an input over-voltage condition or over-voltage battery
condition exists at the time of the device enable, then
the OVP switch will remain OFF and FLT is always low.
AAT4685
Over-Voltage Protection Switch with OCP and BOVPOVPSwitchTM
PRODUCT DATASHEET
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Under-Voltage Lockout (UVLO)
The AAT4685 has a fixed 2.7V under-voltage lockout
level (UVLO) trip level for IN rising. When the input volt-
age is less than 2.7V - VUVLO_HYS, the OVP switch is turned
off. 100mV of hysteresis is included to ensure circuit
stability.
Over-Voltage Protection (OVP)
The AAT4685 adjustable version has a 1.0V ± 3% over-
voltage trip threshold on the OVP pin. With a resistor
divider on OVP pin from IN to GND, the over-voltage
protection point of IN can be adjusted between 4V and
7V. If the over-voltage trip level is triggered, the OVP
switch will start to be turned off in 1s. The FLT pin is
driven low. When the input voltage pin returns below
VOVPT – VOVP_HYS (but is still above VUVLO), the OVP switch
is turned on again after a TOVP_REC recovery time to ensure
that the input supply has stabilized.
Fixed OVP products are also available where the resistive
divider is internally integrated. Pin 12 is designed to be
not connected.
Over-Current Protection (OCP)
The AAT4685 integrates adjustable over-current protec-
tion. Once the load current exceeds the pre-set limit of
IOCP current (ILOAD>IOCP), the load current is limited after
the OCP blanking time (typical 180s). During the OCP
blanking time, the OVP switch stays ON. Once the load
current drops below IOCP
, current restriction will be
removed. If the over-current state continues after the
blanking period, the OVP switch turns off and FLT is
pulled down. In order to prevent the input voltage from
spiking up due to the inductance of the input cable, the
OVP switch is turned off slowly, resulting in a "soft-stop."
The OVP switch will turn back on again after TOCP_REC
(typical 64ms) and the current is monitored all over
again. Each time an OCP fault occurs, an internal counter
is incremented. If 15 OCP faults occur in one charge
cycle, the OVP switch is turned off permanently. The
counter is cleared either by removing and re-applying
input power, or by disabling and re-enabling the device
via the EN pin.
The OCP threshold is set by an external resistor (ROCP)
connected between OCP and ground. IOCP is approxi-
mated by the following formula:
IOCP = (current in A, resistance in kΩ)
30
ROCP
Battery Over-Voltage Protection (BOVP)
The AAT4685 monitors the positive battery terminal and
turns the OVP switch off when the battery voltage
exceeds the BOVP threshold (typical 4.35V). The monitor
has blanking time TBOVP_BL (typical 180s) to prevent any
transient voltage from false triggering the BOVP. A resis-
tor is required between the BOVP pin and the battery, to
limit the current in case of a short circuit condition. If the
battery voltage exceeds the BOVP trip threshold VBOVPT
,
the OVP switch is turned off, and the FLT pin is driven
low. In order to prevent the input voltage from spiking
up due to the inductance of the input cable, the OVP
switch is turned off slowly , resulting in a "soft-stop." The
OVP switch is turned back on once the battery voltage
drops to VBOVPT – VBOVP_HYS. Each time a battery over-
voltage fault occurs, an internal counter is incremented.
If 15 such faults occur in one charge cycle, the OVP
switch is turned off permanently. The counter is cleared
either by removing and re-applying input power, or by
disabling and re-enabling the device via the EN pin.
Over-Temperature Protection
(OT Protection)
If the junction temperature of the device exceeds TSHDN,
the OVP switch is turned off, and the FLT pin is driven
low. The OVP switch is turned back on when the junction
temperature falls below TSHDN - 15°C.
Fault Indicator (FLT)
The FLT output is an active-low open-drain fault (OV/OC/
BOVP/OT) reporting output. A pull-up resistor should be
connected from FLT to the logic I/O voltage of the host
system. When EN is low, FLT is asserted by pulling down
in the case of an over-voltage, over-current, or battery
over-voltage or over-temperature fault occuring; FLT is
de-asserted into high impedance state with the fault
removed. When EN is high, FLT is in high impedance
status.
AAT4685
Over-Voltage Protection Switch with OCP and BOVPOVPSwitchTM
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Enable Control (EN)
EN is an active low enable with internal 200k resistor
pulled down to GND. EN is driven low, connected to
ground, or left floating for normal device operation. Set
EN low to turn the OVP switch on after turn on delay
time. Set EN high to turn the OVP switch off. In the case
of an over-voltage or UVLO condition toggling EN will not
override the fault condition and the OVP switch will
remain off. The OCP counter and the BOVP counter are
both reset when the device is re-enabled by the EN pin.
IC Input
Internally connected to GND through a 100k resistor.
Connect this pin to ground.
Power–OK Indicator (POK)
The AAT4685 contains an open-drain POK output that
goes low when a valid input source is detected at the IN
pin. The valid input range is between VUVLO (typical 2.7V)
and VOVP voltage (fixed 5.85V / fixed 6.8V / adjustable
OVP threshold set by external resistors). After a valid
input has been established, charging is sustained. The
POK function is always active whether the EN pin is at
low or high state.
Device Start-Up Operation
On initial power-up, if VUVLO < IN < VOVP
, VBAT < VBOVP
, and
EN is low, the OVP switch starts to turn on after TON delay
time (typical 8ms) to be stabilized for input. This turn on
uses Soft Start to control the inrush current to minimize
ringing at the input. Because of the deglitch time at
power on, if the input voltage rises rapidly past the OVP
threshold, the device does not switch on at all; instead
it goes into protection mode and indicate a fault on the
FLT pin. After successful start-up, if ILOAD > IOCP limit the
device turns off and the fault flag is asserted.
The Soft Start function is defined as follows: "current
limit is stepped digitally from low level to its final current
limit level for soft starting."
AAT4685
Over-Voltage Protection Switch with OCP and BOVPOVPSwitchTM
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System Flowchart
FLT state
FLT state
FLT state
Turn Off OVP
swtch,
FLT = L
VBAT > BOVP
Y
VIN > OVP
N
Blanking Time
180μs
Y
NN
count <15 ?
Turn Off OVP
switch,
FLT = L,
Incr BOVP counter
I > IOCP
V(IN) < OVP Wait tOVP_ REC
(8ms )
EN = H
Blanking Time
180μs
Y
N
Turn Off OVP
switch,
FLT = L,
Incr OCP counter
count <15 ?
EN = H
Wait tOCP_ REC
(64ms)
N
Y
N
Y
N
Y
N
Y
N
Y
Y
N
Y
VBAT < BOVP
Goto
Standby
Goto
Standby
N
Y
FLT state
Turn Off OVP
swtch,
FLT = HiZ
Y
TJ > TSHDN
N
TJ < T SHDN -15
N
Y
Limit
Current
Power ON
UVLO : ON
V(IN) > UVLO N
Y
Turn On OVP
switch,
FLT = HiZ
OVP : ON
All functions OFF
Reset :
Timers reset
Counters reset
FLT = HiZ
EN = L N
Y
BOVP, TSD : ON
FLT=HiZ
OCP : ON
N
Y
Wait tDGL
(8ms)
Standby
Any State :
If V(IN) < UVLO go to “Power ON”
If EN = H go to “Standby”
AAT4685
Over-Voltage Protection Switch with OCP and BOVPOVPSwitchTM
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Application Information
Over-Voltage Protection Resistors
The over-voltage protection threshold is programmed
with two resistors, R1 and R2. To limit the current going
through the external resistor string while maintaining
good noise immunity, use smaller resistor values, such as
10k for R2. Using a larger value will further reduce the
system current, but will also increase the impedance of
the OVP node, making it more sensitive to external noise
and interference. A suggested value for R2 is 100k. R1
can be calculated using the following equation:
R1 = - 1 · R2 = (VOVP - 1) · 100
VOVP
VOVP_TH
Table 1 summarizes 1% standard metal film resistors for
several over-voltage settings.
R2 (kΩ) R1 (kΩ)V
OVP Setting (V)
100 300 4.0
100 348 4.5
100 402 5.0
100 442 5.5
100 499 6.0
100 549 6.5
100 604 7.0
Table 1: 1% Standard Resistor Values
for OVP Setting.
Over-Current Protection Resistor
The over-current threshold is programmed by an exter-
nal resistor (ROCP) connected from the OCP pin to GND.
ROCP can be calculated by the following equation.
ROCP = · 1000
30
IOCP
Table 2 summarizes 1% standard metal film resistors for
several over-current settings.
R3 (kΩ)I
OCP Setting (A)
100.0 0.30
86.6 0.35
75.0 0.40
66.5 0.45
60.4 0.50
54.9 0.55
49.9 0.60
43.0 0.70
37.4 0.80
33.2 0.90
30.1 1.00
24.9 1.20
21.5 1.40
18.7 1.60
16.5 1.80
Table 2: 1% Standard Resistor Values
for OCP Setting.
Input Capacitor
A 1F or larger capacitor is typically recommended for
CIN. CIN should be located as close to the device IN pin as
practically possible. Ceramic, tantalum, or aluminum
electrolytic capacitors may be selected for CIN. There is
no specific capacitor equivalent series resistance (ESR)
requirement for CIN. However, for higher current opera-
tion, ceramic capacitors are recommended for CIN due to
their inherent capability over tantalum capacitors to
withstand input current surges from low impedance
sources such as batteries in portable devices.
Capacitors are typically manufactured in different volt-
age ratings. If the maximum possible surge voltage is
known, select capacitors with a voltage rating at least 5V
higher than the maximum possible surge voltage. 50V
rated capacitors are generally good for most OVP appli-
cations to prevent any surge voltage.
AAT4685
Over-Voltage Protection Switch with OCP and BOVPOVPSwitchTM
PRODUCT DATASHEET
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Output Capacitor
In order to insure stability while current limit is active, a
small output capacitance of approximately 1F is required
at the output. Likewise, with the output capacitor, there
is no specific capacitor ESR requirement. If desired, COUT
may be increased to accommodate any load transient
condition.
PCB Layout Recommendations
For proper thermal management and to take advantage
of the low RDS (ON) of the AAT4685, certain circuit board
layout rules should be followed:
1. VIN and VOUT should be routed using wider than nor-
mal traces.
2. GND should be connected to a ground plane. The
ground plane area connected to the ground pins
should be made as large as possible. Exposed pad
should be connected to ground plane to get best
power dissipation.
3. For best performance, CIN and COUT should be placed
close to the IN and OUT pins.
Evaluation Board Schematic
C1
1μF
C2
1μF
VIN
R3
30k
Green LED
Disable
VOUT
AAT4685
IC
2
OCP
1
EN
3
BOVP 11
OVP
12
POK 4
OUT 5
GND 9
FLT 10
IN
8
OUT 6
IN
7
U1
R1
604k
R5
1.74k
R6
1.74k
R4
100k
R2
100k
+5V
+5V
Red LED
1 2
BATT
Figure 1: AAT4685 Evaluation Board Schematic.
AAT4685
Over-Voltage Protection Switch with OCP and BOVPOVPSwitchTM
PRODUCT DATASHEET
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Evaluation Board Layout
Figure 2: AAT4685 Evaluation Board Figure 3: AAT4685 Evaluation Board
Top Side Layout. Bottom Side Layout.
Evaluation Board Bill of Materials
Designator Part Number Description Manufacturer
U1 AAT4685IWP-1-T1 IC Over-Voltage Protection Switch with OCP AATI
C1, C2 GRM21BR71H105K Cap Ceramic 1F 0805 X7R 50V 10% Murata
R1 RC0603FR-07604KL Res 604k 1/10W 1% 0603 SMD
Yageo
R3 RC0603FR-0730K1L Res 30.1K 1/10W 1% 0603 SMD
R2, R4 RC0603FR-07100KL Res 100K 1/10W 1% 0603 SMD
R5, R6 RC0603FR-071K74RL Res 1.74k 1/10W 1% 0603 SMD
LED1 0805KRCT LED Red 0805 HB
LED2 0805KGCT LED Green 0805
Table 3: AAT4685 Evaluation Board Bill of Materials (BOM).
AAT4685
Over-Voltage Protection Switch with OCP and BOVPOVPSwitchTM
PRODUCT DATASHEET
16 4685.2009.03.1.0
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1. XYY = assembly and date code.
2. Sample stock is generally held on part numbers listed in BOLD.
3. The leadless package family, which includes QFN, TQFN, DFN, TDFN and STDFN, has exposed copper (unplated) at the end of the lead terminals due to the manufacturing
process. A solder fillet at the exposed copper edge cannot be guaranteed and is not required to ensure a proper bottom solder connection.
Ordering Information
Package OVP Trip Voltage Marking1Part Number (Tape and Reel)2
TDFN33-12 Adjustable 8LXYY AAT4685IWP-1-T1
TDFN33-12 6.80V AAT4685IWP-2-T1
TDFN33-12 5.85V AAT4685IWP-3-T1
All AnalogicTech products are offered in Pb-free packaging. The term “Pb-free” means semiconductor
products that are in compliance with current RoHS standards, including the requirement that lead not exceed
0.1% by weight in homogeneous materials. For more information, please visit our website at
http://www.analogictech.com/about/quality.aspx.
Packaging Information
TDFN33-12
Top View Bottom View
Detail "A"
Side View
3.00
±
0.05
Index Area Detail "A"
1.70
±
0.05
3.00
±
0.05
0.05
±
0.05
0.23
±
0.05
0.75
±
0.05
2.40
±
0.05
Pin 1 Indicator
(optional)
0.43
±
0.05
0.45
±
0.050.23
±
0.05
0.1 REF
C0.3
All dimensions in millimeters.
AAT4685
Over-Voltage Protection Switch with OCP and BOVPOVPSwitchTM
PRODUCT DATASHEET
4685.2009.03.1.0 17
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Phone (408) 737-4600
Fax (408) 737-4611
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