Active-Semi ACT4523 Rev 4, 21-Jul-11

Wide-Input Sensorless CC/CV Step-Down DC/DC Converter

FEATURES APPLICATIONS
• 40V Input Voltage Surge • Car Charger/ Adaptor
• 38V Steady State Operation • Rechargeable Portable Devices
• Up to 3A output current • General-Purpose CC/CV Supply
• Output Voltage up to 12V
• Patent Pending Active CC Sensorless Constant GENERAL DESCRIPTION
Current Control ACT4523 is a wide input voltage, high efficiency
− Integrated Current Control Improves Active CC step-down DC/DC converter that
Efficiency, Lowers Cost, and Reduces operates in either CV (Constant Output Voltage)
Component Count mode or CC (Constant Output Current) mode.
• Resistor Programmable ACT4523 provides up to 3A output current at
225kHz switching frequency.
− Current Limit from 1.5A to 3A
Active CC is a patent-pending control scheme to
− Patented Cable Compensation from 0Ω to achieve highest accuracy sensorless constant
0.3Ω
current control. Active CC eliminates the expensive,
• ±7.5% CC Accuracy high accuracy current sense resistor, making it ideal
− Compensation of Input /Output Voltage Change for battery charging applications and adaptors with
accurate current limit. The ACT4523 achieves
− Temperature Compensation
higher efficiency than traditional constant current
− Independent of inductance and Inductor DCR switching regulators by eliminating its associated
• 2% Feedback Voltage Accuracy power loss.
• Up to 94% Efficiency Protection features include cycle-by-cycle current
• 225kHz Switching Frequency Eases EMI Design limit, thermal shutdown, and frequency foldback at
• Advanced Feature Set short circuit. The devices are available in a SOP-
8EP package and require very few external devices
− Integrated Soft Start for operation.
− Thermal Shutdown
− Secondary Cycle-by-Cycle Current Limit
− Protection Against Shorted ISET Pin
• SOP-8EP Package

CC/CV Curve
C3
6.0
ACT4523-001

22nF
Input 10V to 40V HSB 5V
50V
IN SW VIN = 24V
L1 30µH 5.0
ACT4523
Output Voltage (V)

ENABLE EN FB 4.0
ISET GND COMP R2 52k VIN = 12V

3.0
C1 R1 C2 R4 D1 C4
47µF 11.5k 2.2nF 10k SK34 220µF 2.0
R3
8.2k
1.0

0.0
0 0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2

Output Current (A)

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Copyright © 2011 Active-Semi, Inc.
 Active-Semi ACT4523
Rev 4, 21-Jul-11

ORDERING INFORMATION
PART NUMBER OPERATION TEMPERATURE RANGE PACKAGE PINS PACKING
ACT4523YH-T -40°C to 85°C SOP-8EP 8 TAPE & REEL

PIN CONFIGURATION

PIN DESCRIPTIONS

PIN NAME DESCRIPTION

High Side Bias Pin. This provides power to the internal high-side MOSFET gate driver.
1 HSB
Connect a 22nF capacitor from HSB pin to SW pin.
Power Supply Input. Bypass this pin with a 10µF ceramic capacitor to GND, placed as
2 IN
close to the IC as possible.
3 SW Power Switching Output to External Inductor.
Ground. Connect this pin to a large PCB copper area for best heat dissipation. Return
4 GND FB, COMP, and ISET to this GND, and connect this GND to power GND at a single
point for best noise immunity.
Feedback Input. The voltage at this pin is regulated to 0.808V. Connect to the resistor
5 FB
divider between output and GND to set the output voltage.
6 COMP Error Amplifier Output. This pin is used to compensate the converter.
Enable Input. EN is pulled up to 5V with a 4μA current, and contains a precise 1.6V
7 EN logic threshold. Drive this pin to a logic-high or leave unconnected to enable the IC.
Drive to a logic-low to disable the IC and enter shutdown mode.
Output Current Setting Pin. Connect a resistor from ISET to GND to program the
8 ISET
output current.
Heat Dissipation Pad. Connect this exposed pad to large ground copper area with
Exposed Pad
copper and vias.

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 Active-Semi ACT4523
Rev 4, 21-Jul-11

ABSOLUTE MAXIMUM RATINGSc

PARAMETER VALUE UNIT
IN to GND -0.3 to 40 V
SW to GND -1 to VIN + 1 V
HSB to GND VSW - 0.3 to VSW + 7 V
FB, EN, ISET, COMP to GND -0.3 to + 6 V
Junction to Ambient Thermal Resistance 46 °C/W
Operating Junction Temperature -40 to 150 °C
Storage Junction Temperature -55 to 150 °C
Lead Temperature (Soldering 10 sec.) 300 °C

c: Do not exceed these limits to prevent damage to the device. Exposure to absolute maximum rating conditions for long periods may
affect device reliability.

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 Active-Semi ACT4523
Rev 4, 21-Jul-11

ELECTRICAL CHARACTERISTICS
(VIN = 20V, TA = 25°C, unless otherwise specified.)

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

Input Voltage 10 38 V
Input Voltage Surge 40 V
VIN UVLO Turn-On Voltage Input Voltage Rising 9.0 9.4 9.7 V
VIN UVLO Hysteresis Input Voltage Falling 1.1 V
VEN = 3V, VFB = 1V 0.9 1.4 mA
Standby Supply Current
VEN = 3V, VOUT = 5V, No load 3.0 mA
Shutdown Supply Current VEN = 0V 75 115 µA
Feedback Voltage 792 808 824 mV
Internal Soft-Start Time 400 µs
VFB = VCOMP = 0.8V,
Error Amplifier Transconductance 650 µA/V
∆ICOMP = ± 10µA
Error Amplifier DC Gain 4000 V/V
Switching Frequency VFB = 0.808V 200 225 250 kHz
Foldback Switching Frequency VFB = 0V 30 kHz
Maximum Duty Cycle 85 88 91 %
Minimum On-Time 200 ns
COMP to Current Limit Transconductance VCOMP = 1.2V 5.25 A/V
Secondary Cycle-by-Cycle Current Limit Duty = DMAX 4.5 A
Slope Compensation Duty = DMAX 1.2 A
ISET Voltage 1 V

ISET to IOUT DC Room Temp Current Gain IOUT / ISET, RISET = 19.6kΩ 25000 A/A

RISET = 19.6kΩ, VOUT = 3.5V

CC Controller DC Accuracy 1175 1190 1205 mA
Open-Loop DC Test
EN Threshold Voltage EN Pin Rising 1.47 1.6 1.73 V
EN Hysteresis EN Pin Falling 125 mV
EN Internal Pull-up Current 4 µA
High-Side Switch ON-Resistance 0.16 Ω
SW Off Leakage Current VEN = VSW = 0V 1 10 µA
Thermal Shutdown Temperature Temperature Rising 150 °C

Thermal Shutdown Temperature Hysteresis Temperature Falling 20 °C

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 Active-Semi ACT4523
Rev 4, 21-Jul-11

FUNCTIONAL BLOCK DIAGRAM

IN
AVIN PVIN

BANDGAP,
REGULATOR,
EMI
EN & OSCILLATOR
CONTROL HSB
SHUTDOWN VREF = 0.808V
CONTROL

PWM
Σ CONTROLLER

SW

VREF = 0.808V
+ CC
CONTROL
FB -

COMP ISET

FUNCTIONAL DESCRIPTION
CV/CC Loop Regulation regulating output voltage to regulating output
current, and the output voltage will drop with
As seen in Functional Block Diagram, the ACT4523
increasing load.
is a peak current mode pulse width modulation
(PWM) converter with CC and CV control. The The Oscillator normally switches at 225kHz.
converter operates as follows: However, if FB voltage is less than 0.6V, then the
switching frequency decreases until it reaches a
A switching cycle starts when the rising edge of the
typical value of 30kHz at VFB = 0.15V.
Oscillator clock output causes the High-Side Power
Switch to turn on and the Low-Side Power Switch to Enable Pin
turn off. With the SW side of the inductor now
The ACT4523 has an enable input EN for turning
connected to IN, the inductor current ramps up to
the IC on or off. The EN pin contains a precision
store energy in the magnetic field. The inductor
1.6V comparator with 125mV hysteresis and a 4µA
current level is measured by the Current Sense
pull-up current source. The comparator can be used
Amplifier and added to the Oscillator ramp signal. If
with a resistor divider from VIN to program a startup
the resulting summation is higher than the COMP
voltage higher than the normal UVLO value. It can
voltage, the output of the PWM Comparator goes
be used with a resistor divider from VOUT to disable
high. When this happens or when Oscillator clock
charging of a deeply discharged battery, or it can be
output goes low, the High-Side Power Switch turns
used with a resistor divider containing a thermistor
off.
to provide a temperature-dependent shutoff
At this point, the SW side of the inductor swings to protection for over temperature battery. The
a diode voltage below ground, causing the inductor thermistor should be thermally coupled to the
current to decrease and magnetic energy to be battery pack for this usage.
transferred to output. This state continues until the
If left floating, the EN pin will be pulled up to roughly
cycle starts again. The High-Side Power Switch is
5V by the internal 4µA current source. It can be
driven by logic using HSB as the positive rail. This
driven from standard logic signals greater than
pin is charged to VSW + 5V when the Low-Side
1.6V, or driven with open-drain logic to provide
Power Switch turns on. The COMP voltage is the
digital on/off control.
integration of the error between FB input and the
internal 0.808V reference. If FB is lower than the Thermal Shutdown
reference voltage, COMP tends to go higher to
The ACT4523 disables switching when its junction
increase current to the output. Output current will
temperature exceeds 150°C and resumes when the
increase until it reaches the CC limit set by the ISET
temperature has dropped by 20°C.
resistor. At this point, the device will transition from
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 Active-Semi ACT4523
Rev 4, 21-Jul-11

APPLICATIONS INFORMATION
Output Voltage Setting CC Current Line Compensation
When operating at constant current mode, the
Figure 1: current limit increase slightly with input voltage. For
Output Voltage Setting wide input voltage applications, a resistor RC is
added to compensate line change and keep output
VOUT high CC accuracy, as shown in Figure 3.
Figure 3:
ACT4523 RFB1
Iutput Line Compensation
FB
RFB2

Figure 1 shows the connections for setting the

output voltage. Select the proper ratio of the two
feedback resistors RFB1 and RFB2 based on the
output voltage. Typically, use RFB2 ≈ 10kΩ and
determine RFB1 from the following equation:

⎛ V ⎞
R FB1 = R FB 2 ⎜ OUT − 1 ⎟ (1) Inductor Selection
⎝ 0 . 808 V ⎠ The inductor maintains a continuous current to the
output load. This inductor current has a ripple that is
CC Current Setting dependent on the inductance value:
ACT4523 constant current value is set by a resistor Higher inductance reduces the peak-to-peak ripple
connected between the ISET pin and GND. The CC current. The trade off for high inductance value is
output current is linearly proportional to the current the increase in inductor core size and series
flowing out of the ISET pin. The voltage at ISET is resistance, and the reduction in current handling
roughly 1V and the current gain from ISET to output capability. In general, select an inductance value L
is roughly 25000 (25mA/1µA). To determine the based on ripple current requirement:
proper resistor for a desired current, please refer to
Figure 2 below.
VOUT × (VIN _VOUT )
L= (2)
Figure 2: VIN fSW ILOADMAX K RIPPLE
Curve for Programming Output CC Current
where VIN is the input voltage, VOUT is the output
voltage, fSW is the switching frequency, ILOADMAX is
Output Current vs. RISET
3500
the maximum load current, and KRIPPLE is the ripple
ACT4523-002

factor. Typically, choose KRIPPLE = 30% to

3000 correspond to the peak-to-peak ripple current being
30% of the maximum load current.
2500
Output Current (mA)

With a selected inductor value the peak-to-peak

2000
inductor current is estimated as:
VOUT × (VIN _VOUT )
1500

1000 ILPK _ PK = (3)

L × VIN × fSW
500
VIN = 24V, VOUT = 4V The peak inductor current is estimated as:
0
8 11 14 17 20 23 26 29 32
1
ILPK = ILOADMAX + ILPK _ PK (4)
RISET (kΩ) 2

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 Active-Semi ACT4523
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APPLICATIONS INFORMATION CONT’D

The selected inductor should not saturate at ILPK. Output Capacitor
The maximum output current is calculated as:
The output capacitor also needs to have low ESR to
1 keep low output voltage ripple. The output ripple
IOUTMAX = ILIM _
I _ (5) voltage is:
2 LPK PK
VIN
LLIM is the internal current limit, which is typically VRIPPLE = IOUTMAX K RIPPLE RESR + 2 (6)
28 × fSW LC OUT
3.2A, as shown in Electrical Characteristics Table.

External High Voltage Bias Diode Where IOUTMAX is the maximum output current,
It is recommended that an external High Voltage KRIPPLE is the ripple factor, RESR is the ESR of the
Bias diode be added when the system has a 5V output capacitor, fSW is the switching frequency, L is
fixed input or the power supply generates a 5V the inductor value, and COUT is the output
output. This helps improve the efficiency of the capacitance. In the case of ceramic output
regulator. The High Voltage Bias diode can be a capacitors, RESR is very small and does not
low cost one such as IN4148 or BAT54. contribute to the ripple. Therefore, a lower
capacitance value can be used for ceramic type. In
Figure 4: the case of tantalum or electrolytic capacitors, the
ripple is dominated by RESR multiplied by the ripple
External High Voltage Bias Diode
current. In that case, the output capacitor is chosen
to have sufficiently low ESR.
For ceramic output capacitor, typically choose a
capacitance of about 22µF. For tantalum or
electrolytic capacitors, choose a capacitor with less
than 50mΩ ESR.

Rectifier Diode
Use a Schottky diode as the rectifier to conduct
current when the High-Side Power Switch is off.
This diode is also recommended for high duty cycle The Schottky diode must have current rating higher
operation and high output voltage applications. than the maximum output current and a reverse
voltage rating higher than the maximum input
Input Capacitor voltage.
The input capacitor needs to be carefully selected
to maintain sufficiently low ripple at the supply input
of the converter. A low ESR capacitor is highly
recommended. Since large current flows in and out
of this capacitor during switching, its ESR also
affects efficiency.
The input capacitance needs to be higher than
10µF. The best choice is the ceramic type,
however, low ESR tantalum or electrolytic types
may also be used provided that the RMS ripple
current rating is higher than 50% of the output
current. The input capacitor should be placed close
to the IN and G pins of the IC, with the shortest
traces possible. In the case of tantalum or
electrolytic types, they can be further away if a
small parallel 0.1µF ceramic capacitor is placed
right next to the IC.

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 Active-Semi ACT4523
Rev 4, 21-Jul-11

STABILITY COMPENSATION
Figure 5: If RCOMP is limited to 15kΩ, then the actual cross
over frequency is 6.58 / (VOUTCOUT). Therefore:
Stability Compensation _
6
C COMP = 6 . 45 × 10 VOUT C OUT (F) (14)
STEP 3. If the output capacitor’s ESR is high
enough to cause a zero at lower than 4 times the
cross over frequency, an additional compensation
capacitor CCOMP2 is required. The condition for using
CCOMP2 is:
_6
1 . 77 × 10
R ESRCOUT ≥ (Min ,0 . 006 × VOUT ) (Ω) (15)
C OUT
c: CCOMP2 is needed only for high ESR output capacitor
And the proper value for CCOMP2 is:
The feedback loop of the IC is stabilized by the
components at the COMP pin, as shown in Figure C OUT R ESRCOUT
C COMP 2 = (16)
5. The DC loop gain of the system is determined by R COMP
the following equation:
Though CCOMP2 is unnecessary when the output
0 . 808 V capacitor has sufficiently low ESR, a small value
A VDC = A VEA G COMP (7)
I OUT CCOMP2 such as 100pF may improve stability against
PCB layout parasitic effects.
The dominant pole P1 is due to CCOMP:
Table 1 shows some calculated results based on
G
fP 1 = EA
(8) the compensation method above.
2 π A VEA C COMP
Table 1:
The second pole P2 is the output pole:
Typical Compensation for Different Output
I OUT
fP 2 = (9) Voltages and Output Capacitors
2 π V OUT C OUT
VOUT COUT RCOMP CCOMP CCOMP2c
The first zero Z1 is due to RCOMP and CCOMP:
2.5V 47μF Ceramic CAP 5.6kΩ 3.3nF None
1
fZ 1 = (10) 3.3V 47μF Ceramic CAP 6.2kΩ 3.3nF None
2 π R COMP C COMP
5V 47μF Ceramic CAP 8.2kΩ 3.3nF None
And finally, the third pole is due to RCOMP and 2.5V 470μF/6.3V/30mΩ 39kΩ 22nF 47pF
CCOMP2 (if CCOMP2 is used):
3.3V 470μF/6.3V/30mΩ 45kΩ 22nF 47pF
1
fP 3 = (11) 5V 470μF/6.3V/30mΩ 51kΩ 22nF 47pF
2πR COMP C COMP2
c: CCOMP2 is needed for high ESR output capacitor.
The following steps should be used to compensate CCOMP2 ≤ 47pF is recommended.
the IC:
STEP 1. Set the cross over frequency at 1/10 of the
CC Loop Stability
switching frequency via RCOMP: The constant-current control loop is internally
compensated over the 1500mA-3000mA output
2 π V OUT C OUT f SW
R COMP = range. No additional external compensation is
10 G EA G COMP × 0 . 808 V required to stabilize the CC current.
= 5 . 12 × 10 7 VOUT C OUT (Ω) (12) Output Cable Resistance Compensation
STEP 2. Set the zero fZ1 at 1/4 of the cross over To compensate for resistive voltage drop across the
frequency. If RCOMP is less than 15kΩ, the equation charger's output cable, the ACT4523 integrates a
for CCOMP is: simple, user-programmable cable voltage drop
5
compensation using the impedance at the FB pin.
2 . 83 × 10
C COMP = (F) (13) Use the curve in Figure 6 to choose the proper
R COMP feedback resistance values for cable compensation.

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STABILITY COMPENSATION CONT’D

RFB1 is the high side resistor of voltage divider. power GND with vias or short and wide path.
In the case of high RFB1 used, the frequency 3) Return FB, COMP and ISET to signal GND pin,
compensation needs to be adjusted and connect the signal GND to power GND at a
correspondingly. As show in Figure 7, adding a single point for best noise immunity. Connect
capacitor in paralled with RFB1 or increasing the exposed pad to power ground copper area with
compensation capacitance at COMP pin helps the copper and vias.
system stability.
4) Use copper plane for power GND for best heat
Figure 6: dissipation and noise immunity.
Cable Compensation at Various Resistor Divider 5) Place feedback resistor close to FB pin.
Values
6) Use short trace connecting HSB-CHSB-SW loop
Delta Output Voltage vs. Output Current
Figure 8 shows an example of PCB layout.
ACT4523-003

350
0k
43
=
Delta Output Voltage (mV)

300 B1 k
RF 60
1
=3
250 R FB k
00
=3
1 k
R FB
40
200 =2
1
R FB
00k
150 =2
R FB1 0k
= 15
100 R FB1
k
= 100
RFB1
=5 1 k
50 R FB1

0
0 0.4 0.8 1.2 1.6 2

Output Current (A)

Figure 7:
Frequency Compensation for High RFB1

Figure 8: PCB Layout

PC Board Layout Guidance Figure 9 gives one typical car charger application
When laying out the printed circuit board, the schematic and associated BOM list.
following checklist should be used to ensure proper
operation of the IC.
1) Arrange the power components to reduce the
AC loop size consisting of CIN, IN pin, SW pin
and the schottky diode.
2) Place input decoupling ceramic capacitor CIN as
close to IN pin as possible. CIN is connected

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Figure 9:
Typical Application Circuit for 5V/2.1A Car Charger

Table 2:
BOM List for 5V/2.1A Car Charger

ITEM REFERENCE DESCRIPTION MANUFACTURER QTY

1 U1 IC, ACT4523YH, SOP-8EP Active-Semi 1
2 C1 Capacitor, Electrolytic, 47µF/50V, 6.3х7mm Murata, TDK 1
3 C2 Capacitor, Ceramic, 10µF/50V, 1206, SMD Murata, TDK 1
4 C3 Capacitor, Ceramic, 2.2nF/6.3V, 0603, SMD Murata, TDK 1
5 C4 Capacitor, Ceramic, 22nF/50V, 1206, SMD Murata, TDK 1
6 C5 Capacitor, Electrolytic, 220µF/10V, 6.3х7mm Murata, TDK 1
7 C6 Capacitor, Ceramic, 1µF/10V, 0603, SMD Murata, TDK 1
8 L1 Inductor,33µH, 3A, 20%, SMD Tyco Electronics 1
9 D1 Diode, Schottky, 40V/3A, SK34 Diodes 1
10 D2 Diode, 75V/150mA, LL4148 Good-ARK 1
11 R1 Chip Resistor, 11.5kΩ, 0603, 1% Murata, TDK 1
12 R2 Chip Resistor, 52kΩ, 0603, 1% Murata, TDK 1
13 R3 Chip Resistor, 8.2kΩ, 0603, 5% Murata, TDK 1

14 R4 Chip Resistor, 10kΩ, 0603, 1% Murata, TDK 1

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 Active-Semi ACT4523
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TYPICAL PERFORMANCE CHARACTERISTICS

(L = 33µH, CIN = 10µF, COUT = 47µF, Ta = 25°C, RCOMP = 8.2k, CCOMP1 = 2.2nF, CCOMP2 = NC)

100
Efficiency vs. Load current Switching Frequency vs. Input Voltage
250

ACT4523-004

ACT4523-005
VIN = 12V
95
230

Switching Frequency (kHz)

90
210
Efficiency (%)

85
VIN = 24V 190
80
170
75
150
70
130
65
VOUT = 5V
60 110
10 15 20 25 30 35 40
200 600 1000 1400 1800 2200
Input Voltage (V)
Load Current (mA)

Switching Frequency vs. Feedback Voltage CC Current vs. Temperature

260 2700

ACT4523-007
ACT4523-006
Switching Frequency (kHz)

2600
210
CC Current (mA)

2500

160
2400

110 2300

2200
60
2100

10
2000
0 100 200 300 400 500 600 700 800 900 25 45 65 85 105 125 145

Feedback Voltage (mV) Temperature (°C)

CC Current vs. Input Voltage Maximum Peak Current vs. Duty Cycle
2600 4.2
ACT4523-008

ACT4523-009

4.05
Maximum CC Current (A)

2400
3.9
CC Current (mA)

2200 3.75

3.6
2000
3.45

1800 3.3

3.15
1600
3
10 14 18 22 26 30 34 38 20 30 40 50 60 70

Input Voltage (V) Duty Cycle

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TYPICAL PERFORMANCE CHARACTERISTICS CONT’D

(L = 33µH, CIN = 10µF, COUT = 47µF, Ta = 25°C, RCOMP = 8.2k, CCOMP1 = 2.2nF, CCOMP2 = NC)

Shutdown Current vs. Input Voltage Standby Current vs. Input Voltage
175

ACT4523-010

ACT4523-011
3
160

Standby Supply Current (mA)

Shutdown Current (µA)

2.5
145
2
130
1.5
115
1
100
0.5
85

0
70
10 15 20 25 30 35 40 0 4 8 12 16 20 24 28 32 36 40

Input Voltage (V) Input Voltage (V)

Reverse Leakage Current (VIN Floating) Start up into CC mode

160
ACT4523-012

ACT4523-013
VOUT = 5V
Reverse Leakage Current (µA)

RLORD = 1.5Ω
IISET = 2A
VIN = 12V
120

CH1

80

40

CH2
0

0 1 2 3 4 5 CH1: VOUT, 2V/div

CH2: IOUT, 1A/div
VOUT (V) TIME: 200µs/div

Start up into CC mode SW vs. Output Voltage Ripples

ACT4523-014

ACT4523-015

VOUT = 5V VIN = 12V

RLORD = 1.5Ω VOUT = 5V
IISET = 2A IOUT = 2.1A
VIN = 24V

CH1
CH1

CH2
CH2

CH1: VOUT, 2V/div

CH1: VOUT Ripple, 20mV/div
CH2: IOUT, 1A/div
CH2: SW, 5V/div
TIME: 200µs/div
TIME: 2µs/div

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TYPICAL PERFORMANCE CHARACTERISTICS CONT’D

(L = 33µH, CIN = 10µF, COUT = 47µF, Ta = 25°C, RCOMP = 8.2k, CCOMP1 = 2.2nF, CCOMP2 = NC)

SW vs. Output Voltage Ripple Start up with EN

ACT4523-016

ACT4523-017
VIN = 24V VIN = 12V
VOUT = 5V VOUT = 5V
IOUT = 2.1A IOUT = 2.1A

CH1

CH1

CH2 CH2

CH1: VRIPPLE, 20mV/div CH1: EN, 2V/div

CH2: SW, 10V/div CH2: VOUT, 2V/div
TIME: 2µs/div TIME: 400µs//div

Start up with EN Load Step Waveforms

ACT4523-018

ACT4523-019
VIN = 24V VIN = 12V
VOUT = 5V VOUT = 5V
IISET = 2.1A IISET = 2.1A

CH1

CH1

CH2
CH2

CH1: EN, 2V/div

CH1: VOUT, 200mV/div
CH2: VOUT, 2V/div
CH2: IOUT, 1A/div
TIME: 400µs//div
TIME: 200µs//div

Load Step Waveforms Short Circuit

ACT4523-020

ACT4523-021

VIN = 24V VIN = 12V

VOUT = 5V CH1 VOUT = 5V
IISET = 2.1A IISET = 2.1A

CH1

CH2

CH2

CH1: VOUT, 200mV/div CH1: VOUT, 2V/div

CH2: IOUT, 1A/div CH2: IOUT, 1A/div
TIME: 200µs//div TIME: 100µs//div

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 Active-Semi ACT4523
Rev 4, 21-Jul-11

TYPICAL PERFORMANCE CHARACTERISTICS CONT’D

(L = 33µH, CIN = 10µF, COUT = 47µF, Ta = 25°C, RCOMP = 8.2k, CCOMP1 = 2.2nF, CCOMP2 = NC)

Short Circuit Short Circuit Recovery

ACT4523-022

ACT4523-023
VIN = 24V VIN = 12V
CH1 VOUT = 5V VOUT = 5V
IISET = 2.1A IISET = 2.1A

CH1

CH2

CH2

CH1: VOUT, 2V/div

CH2: IOUT, 1A/div CH1: VOUT, 2V/div
TIME: 100µs//div CH2: IOUT, 2A/div
TIME: 1ms/div

Short Circuit Recovery

ACT4523-024

VIN = 24V
VOUT = 5V
IISET = 2.1A

CH1

CH2

CH1: VOUT, 2V/div

CH2: IOUT, 2A/div
TIME: 1ms/div

Innovative PowerTM - 14 - www.active-semi.com

Copyright © 2011 Active-Semi, Inc.
 Active-Semi ACT4523
Rev 4, 21-Jul-11

PACKAGE OUTLINE
SOP-8EP PACKAGE OUTLINE AND DIMENSIONS
DIMENSION IN DIMENSION IN
SYMBOL MILLIMETERS INCHES
MIN MAX MIN MAX
A 1.350 1.700 0.053 0.067
A1 0.000 0.100 0.000 0.004
A2 1.350 1.550 0.053 0.061
b 0.330 0.510 0.013 0.020
c 0.170 0.250 0.007 0.010
D 4.700 5.100 0.185 0.200
D1 3.202 3.402 0.126 0.134
E 3.800 4.000 0.150 0.157
E1 5.800 6.200 0.228 0.244
E2 2.313 2.513 0.091 0.099
e 1.270 TYP 0.050 TYP
L 0.400 1.270 0.016 0.050
θ 0° 8° 0° 8°

Active-Semi, Inc. reserves the right to modify the circuitry or specifications without notice. Users should evaluate each
product to make sure that it is suitable for their applications. Active-Semi products are not intended or authorized for use
as critical components in life-support devices or systems. Active-Semi, Inc. does not assume any liability arising out of
the use of any product or circuit described in this datasheet, nor does it convey any patent license.
Active-Semi and its logo are trademarks of Active-Semi, Inc. For more information on this and other products, contact
sales@active-semi.com or visit http://www.active-semi.com.

is a registered trademark of Active-Semi.

®

Innovative PowerTM - 15 - www.active-semi.com

Copyright © 2011 Active-Semi, Inc.