AMSCO AS1332

AS1332
D a ta s h e e t
6 5 0 m A , St e p - D o w n D C - D C C o n v e r t e r f o r R F P o w e r A m p l i f i e r s
1 General Description
2 Key Features
The AS1332 is a step-down DC-DC converter designed
to power radiofrequency (RF) power amplifiers (PAs)
from a single Li-Ion battery. The device also achieves
high-performance in mobile phones and similar RF PA
applications.
The AS1332 steps down an input voltage of 2.7V to 5.5V
to output voltages ranging from 1.3V to 3.16V. Using a
VCON analog input, the output voltage is set for
controlling power levels and efficiency of the RF PA.
The RF interferences are minimized due to the fixedfrequency PWM operation. The battery consumption is
reduced to 0.01µA (typ.) during shutdown.
Because of the high switching frequencies (2 MHz) tiny
surface-mount components can be used. Additional to
the small size the amount is also small. Only three
external components are required, an inductor and two
ceramic capacitors.
The AS1332 is available in a 8-pin WL-CSP.
!
PWM Switching Frequency: 2MHz
!
Single Lithium-Ion Cell Operation (2.7V to 5.5V)
!
Dynamic Programmable Output Voltage (1.3V to
3.16V)
!
Maximum load capability of 650mA
!
High Efficiency (96% Typ at 3.6VIN, 3.16VOUT at
400mA) from internal synchronous rectification
!
Current Overload Protection
!
Thermal Overload Protection
!
Soft Start
!
8-pin WL-CSP
3 Applications
The AS1332 is an ideal solution for cellular phones,
hand-held radios, RF PC cards, and battery powered RF
devices.
Figure 1. Typical Application Circuit
VIN
2.7V to 5.5V
VDD
PVIN
10 µF
3.3 µH
VOUT
1.3V to 3.16V
SW
EN
AS1332
VOUT = 2.5 x VCON
FB
4.7 µF
VCON
0.52V to 1.27V
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VCON
PGND
Revision 1.01
AGND
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AS1332
Datasheet - P i n A s s i g n m e n t s
4 Pin Assignments
Figure 2. Pin Configuration
PVIN
A1
VDD
B1
EN
C1
Top View
Bottom View
SW
SW
A2
C2
A3
PGND
B3
AGND
C3
FB
PVIN
A3
AGND
B3
FB
C3
VCON
A2
C2
A1
PVIN
B1
VDD
C1
EN
VCON
Pin Descriptions
Table 1. Pin Descriptions
Pin
Name
PVIN
Pin Number
Description
A1
VDD
B1
EN
C1
VCON
FB
AGND
PGND
C2
C3
B3
A3
SW
A2
+2.7V to + 5.5V Power Supply Voltage. Input to the internal PFET switch.
+2.7V to + 5.5V Analog Supply Input. Bypass this pin to GND with a ≥10µF
capacitor.
Active-High Enable Input. Set this digital input high for normal operation.
For shutdown, set low.
Voltage Control Analog Input. VCON controls VOUT.
Feedback Pin. Connect to the output at the output filter capacitor.
Analog and Control Ground
Power Ground
Switch Pin. Switch node connection to the internal PFET switch and NFET
synchronous rectifier. Limit specification of the AS1332.
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AS1332
Datasheet - A b s o l u t e M a x i m u m R a t i n g s
5 Absolute Maximum Ratings
Stresses beyond those listed in Table 2 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 Electrical
Characteristics on page 4 is not implied. Exposure to absolute maximum rating conditions for extended periods may
affect device reliability.
Table 2. Absolute Maximum Ratings
Parameter
Min
Max
Units
VDD, PVIN to AGND
-0.3
+7
V
PGND to AGND
-0.3
+0.3
V
EN, FB, VCON
AGND - 0.3 VDD + 0.3
V
SW
PGND - 0.3 PVIN + 0.3
V
PVIN to VDD
-0.3
+0.3
V
Operating Temperature Range
-40
+85
ºC
+150
ºC
+150
ºC
+260
ºC
2
kV
5.5
V
650
mA
+125
ºC
Junction Temperature (TJ-MAX)
Storage Temperature Range
-65
Maximum Lead Temperature
(soldering, 10sec)
Comments
7V max
ESD Rating
Human Body Model
HBM MIL-Std. 883E 3015.7 methods
Operating Ratings
Input Voltage Range
2.7
Recommended Load Current
Junction Temperature (TJ) Range
Ambient Temperature (TA) Range
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-40
-40
+85
Revision 1.01
ºC
In applications where high power
dissipation and/or poor package thermal
resistance is present, the maximum
ambient temperature may have to be
derated.
Maximum ambient temperature (TA-MAX)
is dependent on the maximum operating
junction temperature (TJ-MAX-OP =
125ºC), the maximum power dissipation
of the device in the application (PD-MAX),
and the junction-to ambient thermal
resistance of the part/package in the
application (θJA), as given by the
following
equation: TA-MAX = TJ-MAX-OP – (θJA ×
PD-MAX).
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AS1332
Datasheet - E l e c t r i c a l C h a r a c t e r i s t i c s
6 Electrical Characteristics
TA = TJ = -40ºC to +85ºC; PVIN = VDD = EN = 3.6V, unless otherwise noted. Typ values are at TA = 25ºC.
Table 3. Electrical Characteristics
Symbol
VFB,MIN
VFB
VFB,MAX
1
ISHDN
2
IQ
Parameter
Conditions
Min
Typ
Max
Units
Feedback Voltage at Minimum
Setting
VCON = 0.4V
1.21
1.30
1.39
V
Feedback Voltage
VCON = 1.1V
2.693
2.75
2.807
V
Feedback Voltage at Maximum
Setting
VCON = 1.4V
3.03
3.17
3.29
V
Shutdown Supply Current
EN = SW = VCON = 0V
0.01
2
µA
DC Bias Current into VDD
VCON = 1V, FB = 0V,
No Switching
1
1.4
mA
1100
1200
mA
140
200
DC-DC Switches
ILIM,PFET
Switch Peak Current Limit
RDSON(P)
Pin-Pin Resistance for PFET
RDSON(N)
Pin-Pin Resistance for NFET
Current limit is built-in, fixed,
and not adjustable.
935
ISW = 200mA; TA = +25°C
ISW = 200mA
230
ISW = -200mA; TA = +25°C
300
ISW = -200mA
415
485
mΩ
mΩ
Control Inputs
VIH,EN
Logic High Input Threshold
VIL,EN
Logic Low Input Threshold
1.2
IPIN,ENABLE Pin Pull Down Current
V
0.5
V
5
7
µA
VCON,min
VCON Threshold
Commanding VFB,MIN
VCON swept down
0.484
0.52
0.556
V
VCON,max
VCON Threshold
Commanding VFB,MAX
VCON swept up
1.208
1.27
1.312
V
ZCON
VCON Input Resistance
ICON
Control Pin Leakage Current
Gain
VCON to VOUT Gain
3
TA = +25°C
100
kΩ
-10
0.556V ≤ VCON ≤ 1.208V
10
2.5
µA
V/V
Oscillator
FOSC
Internal Oscillator Frequency
1.8
2
2.2
MHz
1. Shutdown current includes leakage current of PFET.
2. IQ specified here is when the part is operating at 100% duty cycle.
3. Derived by input leakage test.
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AS1332
Datasheet - E l e c t r i c a l C h a r a c t e r i s t i c s
System Characteristics
TA = 25ºC; PVIN = VDD = EN = 3.6V, unless otherwise noted. The following parameters are verfied by characterisation
and are not production tested.
Table 4. System Characteristics
Symbol
Parameter
Conditions
Min Typ Max Unit
s
Control Inputs
Time for VOUT to rise from
1.3V to 3.16V
VIN = 4.2V, COUT = 4.7µF,
L = 3.3µH, RLOAD = 5Ω
20
Time for VOUT to fall from
3.16V to 1.3V
VIN = 4.2V, COUT = 4.7µF,
L = 3.3µH, RLOAD = 10Ω
20
CCON
VCON Input Capacitance
VCON = 1V, Test frequency = 100 kHz
Linearity
Linearity in Control
Range 0.556V to 1.208V
VIN = 3.6V,
Monotonic in nature
TRESP
T_ON
Turn-On Time
EN = Low to High, VIN = 4.2V,
(time for output to reach 3.16V from
VOUT = 3.16V, COUT = 4.7µF, IOUT ≤ 1mA
enable low to high transition)
30
µs
-3
210
30
20
pF
+3
%
750
µs
Performance Parameters
η
Efficiency
(L = 3.3µH, DCR ≤ 100mΩ)
VIN = 3.6V, VOUT = 1.3V, IOUT = 90mA
87
VIN = 3.6V, VOUT = 3.16V, IOUT = 400mA
96
VIN = 3V to 4.5V, VOUT = 1.3V,
IOUT = 10mA to 400mA
10
mVp
-p
%
VOUTripple
Ripple voltage, PWM mode
Line_tr
Line transient response
VIN = 600mV perturbance, over Vin range
3V to 5.5V; TRISE = TFALL = 10µs,
VOUT = 1.3V, IOUT = 100mA
50
mVp
k
Load_tr
Load transient response
VIN = 3.1/3.6/4.5V, VOUT = 1.3V, transients
up to 100mA, TRISE = TFALL = 10µs
50
mVp
k
PSRR
VIN = 3.6V, VOUT = 1.3V,
IOUT = 100mA
sine wave perturbation frequency = 10kHz,
amplitude = 100mVp-p
40
dB
1
1. Ripple voltage should measured at COUT electrode on good layout PC board and under condition using suggested inductors and capacitors.
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AS1332
Datasheet - Ty p i c a l O p e r a t i n g C h a r a c t e r i s t i c s
7 Typical Operating Characteristics
Circuit in Figure 31 on page 12, PVIN = VDD = EN = 3.6V, L = 3.3µH (LPS4018-332ML_), CIN = 10µF
(GRM21BR61C106KA01), COUT = 4.7µF (GRM32ER71H475KA88) unless otherwise noted;
Figure 3. IQ vs. VIN; VCON = 2V, FB = 0V, no switching
Figure 4. ISHDN vs. Temperature; VCON = 0V, EN = 0V
0.25
1.4
Vi n=2.7V
Vi n=3.6V
+ 25°C
1.2
Shutdown Current (µA) .
Quiescent Current (mA)
- 45°C
+ 95°C
1
0.8
0.6
0.4
0.2
2.5
3
3.5
4
4.5
5
0.2
Vi n=4.2V
Vi n=5.5V
0.15
0.1
0.05
0
-40
5.5
-15
Supply Voltage (V)
Figure 5. Switching Frequency Variation vs. Temp.
35
60
85
Figure 6. VOUT vs. VIN; VOUT = 1.3V
4
1.39
3
1.36
2
Output Voltage (V)
Switching Frequency Variation (%)
10
Temperature (°C)
1
0
-1
-2
Vi n=2.7V
1.33
1.3
1.27
Vi n=3.6V
1.24
Vi n=4.2V
-3
Iout=50mA
Iout=300mA
Vi n=5.5V
Iout=650mA
-4
-40
1.21
-15
10
35
60
85
Temperature (°C)
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2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Supply Voltage (V)
Revision 1.01
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AS1332
Datasheet - Ty p i c a l O p e r a t i n g C h a r a c t e r i s t i c s
Figure 7. VOUT vs. Temp; VIN = 3.6V, VOUT = 1.3V
Figure 8. VOUT vs. Temp; VIN = 3.6V, VOUT = 3.16V
1.35
3.2
Iout=50mA
1.34
Iout=650mA
1.32
1.31
1.3
1.29
1.28
3.16
3.15
3.14
3.13
3.12
1.26
3.11
-15
10
35
60
Iout=650mA
3.17
1.27
1.25
-40
Iout=300mA
3.18
Output Voltage (V)
1.33
Output Voltage (V)
Iout=50mA
3.19
Iout=300mA
3.1
-40
85
-15
10
Temperature (°C)
Figure 9. Switch Peak Current Limit vs. Temp.
60
85
Figure 10. VCON vs. VOUT; VIN = 4.2V, RLOAD = 8Ω
1.2
3.5
3
1.15
Output Voltage (V)
Peak Current Limit (A)
35
Temperature (°C)
1.1
1.05
2.5
2
1.5
Vi n=2.7V
- 45°C
+ 25°C
Vi n=3.6V
+ 90°C
Vi n=5.5V
1
-40
1
-15
10
35
60
85
0
0.5
1
1.5
2
VCON Voltage (V)
Temperature (°C)
Figure 11. Efficiency vs. VOUT; VIN = 3.6V
Figure 12. Efficiency vs. IOUT; VOUT = 1.3V
100
100
Vi n=2.7V
Vi n=3.25V
95
95
Vi n=3.6V
Vi n=4.2V
Efficiency (%)
Efficiency (%)
Vi n=5.5V
90
85
80
75
90
85
80
75
Rl oad=5Ohm
Rl oad=10Ohm
Rl oad=15Ohm
70
70
1
1.5
2
2.5
3
3.5
Output Voltage (V)
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0
100 200 300
400 500 600 700 800
Output Current (mA)
Revision 1.01
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AS1332
Datasheet - Ty p i c a l O p e r a t i n g C h a r a c t e r i s t i c s
Figure 13. Efficiency vs. IOUT; VOUT = 3.09V
100
Efficiency (%)
95
90
85
80
Vi n=2.7V
Vi n=3.25V
75
Vi n=3.6V
Vi n=4.2V
Vi n=5.5V
70
0
100 200 300
400 500 600 700 800
Output Current (mA)
2V/Div 500mA/DIV
5V/Div
1V/Div
50µs/Div
Revision 1.01
2V/Div 500mA/Div
50µs/Div
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1V/Div
VSW
VOUT
IL
VSW
VOUT
IL
5V/Div
1V/Div
EN
IL
EN
50µs/Div
Figure 17. Shutdown Response; VIN = 4.2V, VOUT =
3.16V, COUT = 4.7µF, RLOAD = 10Ω
2V/Div 500mA/DIV
VOUT
VSW
Figure 16. Startup; VIN = 4.2V, VOUT = 3.16V,
IOUT<1mA, RLOAD = 4.7kΩ
EN
50mA 250mA
200mA/Div
VOUT
IL
IOUT
10µs/Div
5V/Div
Figure 15. Startup; VIN = 3.6V, VOUT = 1.3V,
IOUT<1mA, RLOAD = 4.7kΩ
50mV/Div
Figure 14. Load Transient Response; VIN = 3.6V,
VOUT = 1.3V
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AS1332
Datasheet - Ty p i c a l O p e r a t i n g C h a r a c t e r i s t i c s
VSW
3.16V
1.4V
1.3V
VOUT
0V
VCON
0V
VCON
1.4V
1.3V
VOUT
3.16V
VSW
5V/Div
Figure 19. VCON and Load Transient; VIN = 4.2V,
VCON = 0V to 1.4V, 15Ω/8Ω, same time
5V/Div
Figure 18. VCON Voltage Response; VIN = 4.2V,
VCON = 0V to 1.4V, RLOAD = 10Ω
50µs/Div
50µs/Div
5V/Div
10mV/Div
VSW
VOUT
IL
100mA/Div
5V/Div
1V/Div
Figure 21. Output Voltage Ripple; VIN = 3.6V,
VOUT = 1.3V, IOUT = 200mA
1A/Div
IL
VOUT
VSW
Figure 20. Timed Current Limit Response; VIN = 3.6V,
VOUT = 1.3V, RLOAD = 10Ω
5µs/Div
200ns/Div
Figure 22. VOUT Ripple in Skip Mode; VIN = 3.547V,
VOUT = 3.16V, RLOAD = 5Ω
Figure 23. RDSON (P-Chanel) vs. Temperature;
ISW = 200mA
350
VOUT
20mV/Div
500ns/Div
250
RDSON (m Ω )
IL
500mA/Div
VSW
2V/Div
300
200
150
100
Vi n=2.7V
50
Vi n=3.6V
Vi n=5.5V
0
-40
-15
10
35
60
85
Temperature (°C)
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AS1332
Datasheet - Ty p i c a l O p e r a t i n g C h a r a c t e r i s t i c s
Figure 24. RDSON (N-Chanel) vs. Temp.; ISW=-200mA
Figure 25. EN High Threshold vs. VIN
350
1.2
EN High Threshold (V)
300
R DSON (m Ω )
250
200
150
100
Vi n=2.7V
50
1.1
1
0.9
0.8
- 45°C
Vi n=3.6V
+25°C
Vi n=5.5V
0
-40
+90°C
0.7
-15
10
35
60
85
2.7
3.1
3.5
Temperature (°C)
Figure 26. VCON Threshold min vs. VIN
4.3
4.7
5.1
0.52
1.27
0.518
1.268
0.516
0.514
0.512
0.51
0.508
0.506
0.504
1.266
1.264
1.262
1.26
1.258
1.256
1.254
- 45°C
0.502
-45°C
1.252
+25°C
+25°C
+90°C
+90°C
0.5
1.25
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
2.7
3.1
Supply Voltage (V)
3.5
3.9
4.3
4.7
5.1
5.5
Supply Voltage (V)
Figure 28. VFB min vs. VIN; VCON = 0.4V, RLOAD = 10Ω
Figure 29. VFB max vs. VIN; VCON = 0.4V, RLOAD=10Ω
3.2
1.39
1.36
3.18
1.33
VFB max (V)
VFB min (V)
5.5
Figure 27. VCON Threshold max vs. VIN
Vcon Threshold max (V)
Vcon Threshold min (V)
3.9
Supply Voltage (V)
1.3
3.16
3.14
1.27
1.24
3.12
- 45°C
- 45°C
+ 25°C
+ 25°C
+ 90°C
+ 90°C
1.21
3.1
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Supply Voltage (V)
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3
3.5
4
4.5
5
5.5
Supply Voltage (V)
Revision 1.01
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AS1332
Datasheet - D e t a i l e d D e s c r i p t i o n
8 Detailed Description
For driving RF power amplifiers in portable devices and battery powered RF devices the AS1332 is a very suitable DCDC converter. The AS1332 features current overload protection, thermal overload shutdown and soft start. Besides
these features the device also displays the following characteristics:
!
Current-mode buck architecture with synchronous rectification for high efficiency.
!
Operation at maximum efficiency over a wide range of power levels from a single Li-Ion battery cell.
!
The maximum load capability of 650mA is provided in PWM mode, wherein the maximum load range may vary
depending on input voltage, output voltage and the selected inductor.
!
Efficiency is of around 96% for a 400mA load with 3.16V output and 3.6V input.
!
For longer battery life, the output voltage can be dynamically programmable from 1.3V (typ) to 3.16V (typ) by
adjusting the voltage on the control pin without the need for external feedback resistors.
Figure 30. AS1332 Block Diagram
VDD
PVIN
Oscillator
Current
Sense
VCON
PWM
COMP
Error
Amplifier
FB
Mosfet
Control
Logic
Clamp
Logic and
Soft Start
SW
Main Control
EN
Shutdown
Control
AS1332
AGND
PGND
AS1332 is fabricated using a 8-pin WL-CSP, which requires special design considerations for implementation. Its fine
bumppitch requires careful board design and precision assembly equipment. This package offers the smallest possible
size, for space-critical applications such as cell phones, where board area is an important design consideration. The
size of the external components is reduced by using a high switching frequency (2MHz). For implementation only three
external power components are required (see Figure 1 on page 1). The 8-pin WL-CSP package is appropriate for
opaque case applications, where its edges are not subject to high intensity ambient red or infrared light. Also the
system controller should set EN low during power-up and other low supply voltage conditions. See Shutdown Mode on
page 13.
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AS1332
Datasheet - D e t a i l e d D e s c r i p t i o n
Figure 31. Typical Operating System Circuit
VIN
2.7V to 5.5V
PVIN
C1
10 µF
VDD
L1
3.3 µH
VOUT
1.3V to 3.16V
AS1332
VOUT = 2.5 x VCON
FB
C2
ON/OFF
EN
System
Controller
DAC
VCON
SW
4.7 µF
AGND
PGND
Operating the AS1332
AS1332’s control block turns on the internal PFET (P-channel MOSFET) switch during the first part of each switching
cycle, thus allowing current to flow from the input through the inductor to the output filter capacitor and load. The
inductor limits the current to a ramp with a slope of around (VIN - VOUT) / L, by storing energy in a magnetic field.
During the second part of each cycle, the controller turns the PFET switch off, blocking current flow from the input, and
then turns the NFET (N-channel MOSFET) synchronous rectifier on. As a result, the inductor’s magnetic field
collapses, generating a voltage that forces current from ground through the synchronous rectifier to the output filter
capacitor and load.
While the stored energy is transferred back into the circuit and depleted, the inductor current ramps down with a slope
around VOUT / L. The output filter capacitor stores charge when the inductor current is high, and releases it when low,
smoothing the voltage across the load. The output voltage is regulated by modulating the PFET switch on time to
control the average current sent to the load. The effect is identical to sending a duty-cycle modulated rectangular wave
formed by the switch and synchronous rectifier at SW to a low-pass filter formed by the inductor and output filter
capacitor.
The output voltage is equal to the average voltage at the SW pin.
While in operation, the output voltage is regulated by switching at a constant frequency and then modulating the
energy per cycle to control power to the load. Energy per cycle is set by modulating the PFET switch on-time pulse
width to control the peak inductor current. This is done by comparing the signal from the current-sense amplifier with a
slope compensated error signal from the voltage-feedback error amplifier. At the beginning of each cycle, the clock
turns on the PFET switch, causing the inductor current to ramp up. When the current sense signal ramps past the error
amplifier signal, the PWM comparator turns off the PFET switch and turns on the NFET synchronous rectifier, ending
the first part of the cycle.
If an increase in load pulls the output down, the error amplifier output increases, which allows the inductor current to
ramp higher before the comparator turns off the PFET. This increases the average current sent to the output and
adjusts for the increase in the load. Before appearing at the PWM comparator, a slope compensation ramp from the
oscillator is subtracted from the error signal for stability of the current feedback loop. The minimum on time of PFET in
PWM mode is 50ns (typ.)
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AS1332
Datasheet - D e t a i l e d D e s c r i p t i o n
Internal Synchronous Rectifier
To reduce the rectifier forward voltage drop and the associated power loss, the AS1332 uses an internal NFET as a
synchronous rectifier. The big advantage of a synchronous rectification is the higher efficiency in a condition where the
output voltage is low compared to the voltage drop across an ordinary rectifier diode. During the inductor current down
slope in the second part of each cycle the synchronous rectifier is turned on. Before the next cycle the synchronous
rectifier is turned off.
There is no need for an external diode because the NFET is conducting through its intrinsic body diode during the
transient intervals before it turns on.
Dynamic Output Voltage Programming
Because of the dynamically adjustable output voltage of the AS1332 there is no need for external feedback resistors.
Through changing the voltage at the analog pin VCON, the output voltage is set from VFB,MIN to VFB,MAX. This is a very
helpful feature because the supply voltage of a PA application can be changed due to the operation mode. For
example, during the data transmission from a handset peak power is needed. In the other states the transmitting power
can be reduced to ensure a longer battery lifetime.
Shutdown Mode
If EN is set to high (>1.2V) the AS1332 is in normal operation mode. During power-up and when the power supply is
less than 2.7V minimum operating voltage, the chip should be turned off by setting EN low. In shutdown mode the
following blocks of the AS1332 are turned off, PFET switch, NFET synchronous rectifier, reference voltage source,
control and bias circuitry. The AS1332 is designed for compact portable applications, such as mobile phones where the
system controller controls operation mode for maximizing battery life and requirements for small package size
outweigh the additional size required for inclusion of UVLO (Under Voltage Lock-Out) circuitry.
Note: Setting the EN digital pin low (<0.5V) places the AS1332 in a 0.01µA (typ.) shutdown mode.
Thermal Overload Protection
To prevent the AS1332 from short-term misuse and overload conditions the chip includes a thermal overload
protection. To block the normal operation mode the device is turning the PFET and the NFET off in PWM mode as
soon as the junction temperature exceeds 150°C. To resume the normal operation the temperature has to drop below
125°C.
Note: Continuing operation in thermal overload conditions may damage the device and is considered bad practice.
Current Limiting
If in the PWM mode the cycle-by-cycle current limit of 1.2A (max.) is reached the current limit feature takes place and
protects the device and the external components. A timed current limiting mode is working when a load pulls the output
voltage down to approximately 0.375V. In this timed current limit mode the inductor current is forced to ramp down to a
safe value. This is achieved by turning off the internal PFET switch and delaying the start of the next cycle for 3.5us.
The synchronous rectifier is also turned off in the timed current limit mode.
The advantage of the timed current limit mode is to prevent the device of the loss of the current control.
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AS1332
Datasheet - A p p l i c a t i o n I n f o r m a t i o n
9 Application Information
Through setting the voltage on the VCON pin (see Table 5) the output voltage of the AS1332 can be programmed from
1.3V (typ) to 3.16V (typ). This feature eliminates the need for external feedback resistors.
If the voltage on the control pin varies from 0.556V to 1.208V, the output voltage will change according to the equation
stated in Table 5. The output voltage is regulated at VFB,MIN as long as the voltage on the control pin is less than
0.484V. If the voltage on the control pin is higher than 1.312V, the output voltage is regulated at VFB,MAX.
Before the control voltage is fed to the error amplifier inputs, the control voltage is clamped internal in the device.
Table 5. Output Voltage Selection
VCON (V)
VOUT (V)
VCON ≤ 0.484
VFB,MIN
0.556 < VCON < 1.208
VOUT = 2.5 x VCON
VCON ≥ 1.312
VFB,MAX
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AS1332
Datasheet - A p p l i c a t i o n I n f o r m a t i o n
External Component Selection
Inductor Selection
For the external inductor, a 3.3µH inductor is recommend. Minimum inductor size is dependant on the desired efficiency and output current. Inductors with low core losses and small DCR at 2MHz are recommended.
Table 6. Recommended Inductors
Part Number
L
DCR
LPS4018-222ML_
2.2µH
0.070Ω
Current Rating Dimensions (L/W/T)
2.9A
3.9x3.9x1.7mm
LPS4018-332ML_
3.3µH
0.080Ω
2.4A
3.9x3.9x1.7mm
LPS4018-472ML_
4.7µH
0.125Ω
1.9A
3.9x3.9x1.7mm
Manufacturer
Coilcraft
www.coilcraft.com
Capacitor Selection
A 10µF capacitor is recommend for CIN as well as a 4.7µF for COUT. Small-sized X5R or X7R ceramic capacitors are
recommend as they retain capacitance over wide ranges of voltages and temperatures.
Input and Output Capacitor Selection
Low ESR input capacitors reduce input switching noise and reduce the peak current drawn from the battery. Also low
ESR capacitors should be used to minimize VOUT ripple. Multi-layer ceramic capacitors are recommended since they
have extremely low ESR and are available in small footprints.
For input decoupling the ceramic capacitor should be located as close to the device as practical. A 4.7µF input capacitor is sufficient for most applications. Larger values may be used without limitations.
A 2.2µF to 10µF output ceramic capacitor is sufficient for most applications. Larger values up to 22µF may be used to
obtain extremely low output voltage ripple and improve transient response.
Table 7. Recommended Capacitors for the Step-Down Converter
Part Number
C
Voltage
Type
Size
GRM21BR60J226ME39
22µF
6.3V
X5R
0805
GRM21BR60J106KE01
10µF
6.3V
X5R
0805
GRM21BR61C475KA88
4.7µF
16V
X5R
0805
GRM188R61C225KE15
2.2µF
16V
X5R
0603
GRM188R61A225KE34
2.2µF
10V
X5R
0603
C0603C475K8PAC7867
4.7µF
10V
X5R
0603
Manufacturer
Murata
www.murata.com
KEMET
www.kemet.com
EN Pin Control
Drive the EN pin using the system controller to turn the AS1332 ON and OFF. Use a comparator, Schmidt trigger or
logic gate to drive the EN pin. Set EN high (>1.2V) for normal operation and low (<0.5V) for a 0.01µA (typ.) shutdown
mode. Set EN low to turn off the AS1332 during power-up and under voltage conditions when the power supply is less
than the 2.7V minimum operating voltage. The part is out of regulation when the input voltage is less than 2.7V.
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AS1332
Datasheet - A p p l i c a t i o n I n f o r m a t i o n
Layout Considerations
The AS1332 converts higher input voltage to lower output voltage with high efficiency. This is achieved with an inductor
based switching topology. During the first half of the switching cycle, the internal PMOS switch turns on, the input
voltage is applied to the inductor, and the current flows from PVDD line to the output capacitor (C2) through the
inductor. During the second half cycle, the PMOS turns off and the internal NMOS turns on. The inductor current
continues to flow via the inductor from the device PGND line to the output capacitor (C2). Referring to Figure 32, the
AS1332 has two major current loops where pulse and ripple current flow. The loop shown in the left hand side is most
important, because pulse current shown in Figure 32 flows in this path. The right hand side is next. The current
waveform in this path is triangular, as shown in Figure 32. Pulse current has many high-frequency components due to
fast di/dt. Triangular ripple current also has wide high-frequency components. Board layout and circuit pattern design
of these two loops are the key factors for reducing noise radiation and stable operation. Other lines, such as from
battery to C1(+) and C2(+) to load, are almost DC current, so it is not necessary to take so much care. Only pattern
width (current capability) and DCR drop considerations are needed.
Figure 32. Current Loop
VIN
2.7V to 5.5V
i
fOSC = 2MHz
+ C1
VDD
PVIN
i
L1
- 10 µF
3.3 µH
VOUT
SW
EN
VOUT = 2.5 x VCON
FB
C2
4.7 µF
VCON
0.52V to 1.27V
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VCON
PGND
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AS1332
Datasheet - P a c k a g e D r a w i n g s a n d M a r k i n g s
10 Package Drawings and Markings
The device is available in a 8-pin WL-CSP
Figure 33. Package Drawings
Top through view
Bottom view
(Ball side)
500
1
500
40 typ.
1
240 typ.
500
33
0±
20
CCC
500
1625 ±20µm
40 µm
A
A
40 µm
320 typ.
1515 ±20µm
600 ±30µm
Notes:
ccc Coplanarity
All dimensions are in µm
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AS1332
Datasheet - O r d e r i n g I n f o r m a t i o n
11 Ordering Information
The device is available as the standard products listed in Table 8.
Table 8. Ordering Information
Part Number
AS1332-BWLT
Marking
ASQW
Description
650mA, DC-DC Step-Down for RF
Delivery Form
Tape and Reel
Package
8-pin WL-CSP
All devices are RoHS compliant and free of halogene substances.
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AS1332
Datasheet
Copyrights
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Trademarks Registered ®. All rights reserved. The material herein may not be reproduced, adapted, merged,
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Therefore, prior to designing this product into a system, it is necessary to check with austriamicrosystems AG for
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Tobelbaderstrasse 30
A-8141 Unterpremstaetten - Graz, Austria
Tel: +43 (0) 3136 500 0
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