AS1332-BWLT - Austriamicrosystems

AS1332

650mA, Step-Down DC-DC Converter for RF Power Amplifiers

www.austriamicrosystems.com/DC-DC_Step-Down/AS1332 Revision 1.02 1 - 19

Datasheet

1 General Description

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 fixed-

frequency PWM operation. The batter y 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. On ly three

external components are required, an inductor and two

ceramic capacitors.

The AS1332 is available in a 8-pin WL-CSP.

2 Key Features

! PWM Switching Frequency: 2MHz

! Single Lithium-Ion Cell Operation (2.7V to 5.5V)

! Dynamic Programmable Outpu t 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. AS1332 - Typical Application Circuit

AS1332

PGND AGND

VCON

PVIN VDD

1.3V to 3.16V

VOUT = 2.5 x VCON

4.7 µF

3.3 µH VOUT

2.7V to 5.5V

VIN

10 µF

0.52V to 1.27V

VCON

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AS1332

Datasheet - Pin A s s i g n m e n t s

4 Pin Assignments

Figure 2. Pin Configuration

Pin Descriptions

Table 1. Pin Description s

Pin Name Pin Number Description

PVIN A1 +2.7V to + 5.5V Power Supply Voltage. Input to the i nternal PFET switch.

VDD B1 +2.7V to + 5.5V Analog Supply Input. Bypass this pin to GND with a ≥10µF

capacitor.

EN C1 Active-High Enable Input. Set this digital input high for normal operation. For

shutdown, set low.

VCON C2 Vo ltage Control Analog Input. VCON controls VOUT.

FB C3 Feedback Pin. Connect to the output at the output filter capacitor.

AGND B3 Analog and Control Ground. Connect this pin with low resistance to PGND.

PGND A3 Power Ground. Connect this pin with low resistance to AGND.

SW A2 Switch Pin. Switch node connection to the internal PFET switch and NFET

synchron ou s rectifier. Limit specification of the AS1332 .

PGND

AGND

PVIN

VDD

EN C2

VCON

PVIN

VDD

PGND

AGND

FB C2

VCON

Bottom ViewTop View

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AS1332

Datasheet - Ab so lu te Ma xi mu m R at in gs

5 Absolute Maximum Ratings

Stresses beyond those list ed 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 othe r 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 Comments

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 7V max

SW PGND - 0.3 PVIN + 0.3 V

PVIN to VDD -0.3 +0.3 V

Operating Temperature Range -40 +85 ºC

Junction Temperature (TJ-MAX)+150 ºC

Storage Temperature Range -65 +150 ºC

Maximum Lead Temperature

(soldering, 10sec) +260 ºC

ESD Rating

Human Body Model 2kVHBM MIL-Std. 883E 3015.7 methods

Operating Ratings

Input Voltage Range 2.7 5.5 V

Recommended Load Current 650 mA

Junction Temperature (TJ) Range -40 +125 ºC

Ambient Temperature (TA) Range -40 +85 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 th ermal

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 - Ele 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 Parameter Conditions Min Typ Max Units

VFB,MIN Feedback Vol tage at Minimum

Setting VCON = 0.4V 1.21 1.30 1.39 V

VFB Feedback Voltage VCON = 1.1V 2.693 2.75 2.807 V

VFB,MAX Feedback Voltage at Maximum

Setting VCON = 1.4V 3.03 3.17 3.29 V

ISHDN1

1. Shutdown current includes leakage current of PFET.

Shutdown Supply Current EN = SW = VCON = 0V 0.01 2 µA

IQ2

2. IQ specified here is when the part is operating at 100% duty cycle.

DC Bias Current into VDD VCON = 1V, FB = 0V,

No Switching 11.4mA

DC-DC Switches

ILIM,PFET Switch Peak Current Limit Current limit is built-in, fixed,

and not adjustable. 935 1100 1200 mA

RDSON(P) Pin-Pin Resistance for PFET ISW = 200mA; TA = +25°C 140 200 mΩ

ISW = 200mA 230

RDSON(N) Pin-Pin Resistance for NFET ISW = -200mA; TA = +25°C 300 415 mΩ

ISW = -200mA 485

Control Inputs

VIH,EN Logic High Input Th re sh ol d 1.2 V

VIL,EN Logic Low Input Threshold 0.5 V

IPIN,ENABLE Pin Pull Down Current 57µA

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 Resistance3

3. Derived by input leakage test.

TA = +25°C 100 kΩ

ICON Control Pin Leakage Current -10 10 µA

Gain VCON to VOUT Gain 0.556V ≤ VCON ≤ 1.208V 2.5 V/V

Oscillator

FOSC Internal Oscillator Frequency 1.8 2 2.2 MHz

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AS1332

Datasheet - Ele 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

Note: All limits are guaranteed. The parameters with min and max values are guaranteed with production tests or

SQC (Statistical Quality Control) methods.

Table 4. System Characteristics

Symbol Parameter Conditions Min Typ Max Unit

Control Inputs

TRESP

Time for VOUT to rise from

1.3V to 3.16V VIN = 4.2V, COUT = 4.7µF,

L = 3.3µH, RLOAD = 5Ω20 30 µs

Time for VOUT to fall from

3.16V to 1.3V VIN = 4.2V, COUT = 4.7µF,

L = 3.3µH, RLOAD = 10Ω20 30

CCON VCON Input Capacitance VCON = 1V, Test frequency = 100 kHz 20 pF

Linearity Linearity in Control

Range 0.556V to 1.208V VIN = 3.6V,

Monotonic in nature -3 +3 %

T_ON T urn-On Time

(time for output to reach 3.16V from

enable low to high transition)

EN = Low to High, VIN = 4.2V,

VOUT = 3.16V, COUT = 4.7µF, IOUT ≤ 1mA 210 750 µs

Performance Parameters

ηEfficiency

(L = 3.3µH, DCR ≤ 100mΩ)VIN = 3.6V, VOUT = 1.3V, IOUT = 90mA 87 %

VIN = 3.6V, VOUT = 3.16V, IOUT = 400mA 96

VOUT-

ripple Ripple voltage, PWM mode1

1. Ripple voltage should measured at COUT electrode on good layout PC board and under condition using sug-

gested inductors and capacitors.

VIN = 3V to 4.5V, VOUT = 1.3V,

IOUT = 10mA to 400mA 10 mVp

-p

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

Load_tr Load transient response VIN = 3.1/3.6/4.5V, VOUT = 1.3V, transients

up to 100mA, TRISE = TFALL = 10µs 50 mVp

PSRR VIN = 3.6V, VOUT = 1.3V,

IOUT = 100mA sine wave perturbation frequency = 10kHz,

amplitude = 100mVp-p 40 dB

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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

0.2

0.4

0.6

0.8

1.2

1.4

2.5 3 3.5 4 4.5 5 5.5

Supply Volt age ( V)

Quiescent Current (mA)

- 45 °C

+ 25° C

+ 95° C

0.05

0.1

0.15

0.2

0.25

-40 -15 10 35 60 85

T e mperatur e ( °C)

Shutdown Cur rent (µA ) .

Vin=2.7V

Vin=3.6V

Vin=4.2V

Vin=5.5V

Figure 5. Switching Frequency Variation vs. Temp. Figure 6. VOUT vs. VIN; VOUT = 1.3V

-4

-3

-2

-1

-40 -15 10 35 60 85

Temper ature ( ° C)

Switching Frequency V ar iation (%)

Vin=2.7V

Vin=3.6V

Vin=4.2V

Vin=5.5V

1.21

1.24

1.27

1.3

1.33

1.36

1.39

2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5

S upply Voltage ( V)

Out put Voltage (V)

Iout=50mA

Iout=300mA

Iout=650mA

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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, V OUT = 3.16V

1.25

1.26

1.27

1.28

1.29

1.3

1.31

1.32

1.33

1.34

1.35

-40 -15 10 35 60 85

T emperat ur e ( °C)

Out put Voltage (V)

Iout=50mA

Iout=300mA

Iout=650mA

3.1

3.11

3.12

3.13

3.14

3.15

3.16

3.17

3.18

3.19

3.2

-40 -15 10 35 60 85

T e mperatur e ( °C)

Out put Voltage (V)

Iout=50mA

Iout=300mA

Iout=650mA

Figure 9. Switch Pe ak C urre n t Li mi t vs. Temp. Figure 10. VCON vs. VOUT; VIN = 4.2V, RLOAD = 8Ω

1.05

1.1

1.15

1.2

-40 -15 10 35 60 85

T emperat ur e ( °C)

Peak Current Limit (A)

Vin=2.7V

Vin=3.6V

Vin=5.5V 1

1.5

2.5

3.5

00.511.52

VCON Volt age ( V)

Out put Voltage (V)

- 45 °C

+ 25° C

+ 90° C

Figure 11. Efficiency vs. VOUT; VIN = 3.6V Figure 12. Efficiency vs. IOUT; VOUT = 1.3V

100

11.522.533.5

O utput Volt age ( V)

Ef f iciency (%)

Rload=5Ohm

Rload=10Ohm

Rload=15Ohm 70

100

0 100 200 300 400 500 600 700 800

Output Current (mA)

Ef f iciency (%)

Vin=2.7V

Vin=3.25V

Vin=3.6V

Vin=4.2V

Vin=5.5V

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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

0 100 200 300 400 500 600 700 800

Output Current (mA)

Efficiency (%)

Vin=2.7V

Vin=3.25V

Vin=3.6V

Vin=4.2V

Vin=5.5V

Figure 14. Load Transient Response; VIN = 3.6V,

VOUT = 1.3V Figure 15. Startup; VIN = 3.6V, VOUT = 1.3V,

IOUT<1mA, RLOAD = 4.7kΩ

10µs/Div

250mA 50mV/Div 200mA/Div

VOUT

IOUT

50mA

50µs/Div

500mA/DIV 5V/Div

VSW

ILVOUTEN

1V/Div

2V/Div

Figure 16. Startup; VIN = 4.2V, VOUT = 3.16V,

IOUT<1mA, RLOAD = 4.7kΩ Figure 17. Shutdown Response; VIN = 4.2V, VOUT =

3.16V, COUT = 4.7µF, RLOAD = 10Ω

500mA/DIV 5V/Div

VSW

50µs/Div

VOUTEN

1V/Div

2V/Div

50µs/Div

500mA/Div 5V/Div

1V/Div

2V/Div

VSW

ILVOUTEN

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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 18. VCON Voltage Response; VIN = 4.2V,

VCON = 0V to 1.4V, RLOAD = 10Ω Figure 19. VCON and Load Transient; VIN = 4.2V,

VCON = 0V to 1.4V, 15Ω/8Ω, same time

50µs/Div

5V/Div

VSW

VOUT

VCON

1.3V

0V 1.4V 3.16V

50µs/Div

1.3V 5V/Div

VSW

VOUT

VCON

1.4V 3.16V

Figure 20. Timed Current Limit Response; VIN = 3.6V,

VOUT = 1.3V, RLOAD = 10ΩFigure 21. Output Voltage Ripple; VIN = 3.6V,

VOUT = 1.3V, IOUT = 200mA

5µs/Div

1A/Div 5V/Div

1V/Div

VSW

ILVOUT

200ns/Div

100mA/Div 5V/Div

VSW

ILVOUT

10mV/Div

Figure 22. VOUT Ripple in Skip Mode; VIN = 3.547 V,

VOUT = 3.16V, RLOAD = 5

Figure 23. RDSON (P-Chanel) vs. Temperature;

ISW = 200mA

500ns/Div

20mV/Div 2V/Div

500mA/Div

VSW

VOUT

100

150

200

250

300

350

-40 -15 10 35 60 85

Temper ature ( ° C)

RDSON (m )

Vin=2.7V

Vin=3.6V

Vin=5.5V

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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. T emp.; ISW=-200mA Figure 25. EN High Threshold vs. VIN

100

150

200

250

300

350

-40 -15 10 35 60 85

Temper ature ( ° C)

RDSON (m )

Vin=2.7V

Vin=3.6V

Vin=5.5V

0.7

0.8

0.9

1.1

1.2

2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5

Supply Volt age ( V)

E N High Thr esh old ( V )

- 45 °C

+ 25°C

+ 90°C

Figure 26. VCON Threshold min vs. VIN Figure 27. VCON Threshold max vs. VIN

0.5

0.502

0.504

0.506

0.508

0.51

0.512

0.514

0.516

0.518

0.52

2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5

Supply Volt age ( V)

Vcon Threshold min (V)

- 45 °C

+ 25°C

+ 90°C 1.25

1.252

1.254

1.256

1.258

1.26

1.262

1.264

1.266

1.268

1.27

2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5

Supply Volt age ( V)

Vcon Threshold max (V)

-45°C

+25°C

+90°C

Figure 28. VFB min vs. VIN; VCON = 0.4V, RLOAD = 10

Figure 29. VFB max vs. VIN; VCON = 0.4V, RLOAD=10

1.21

1.24

1.27

1.3

1.33

1.36

1.39

2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5

S upply Volt age ( V)

VFB min (V)

- 4 5° C

+ 25°C

+ 90°C 3.1

3.12

3.14

3.16

3.18

3.2

33.544.555.5

S upply Volt age ( V)

VFB max (V)

- 4 5° C

+ 25°C

+ 90°C

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AS1332

Datasheet - D et a i l e d De 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 DC-

DC converter. The AS1332 features current overload protection, thermal overload shutdown and soft start. Besides

these features the device also di splays 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 th e 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 inpu t.

! For longer battery life, th e output voltage can be dynamically pr ogrammable 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

AS1332 is fabricated using a 8-pi n 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.

Mosfet

Control

Logic

Shutdown

Control

Main Control

Clamp

Logic and

Soft Start

Oscillator

Current

Sense

PVIN

PWM

COMP

VDD

Error

Amplifier

VCON

AGND PGND

AS1332

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AS1332

Datasheet - D et a i l e d De s c r i p t i o n

Figure 31. Typical Operating Syste m Circuit

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-ch annel MOSFET) synchronous rectifier on. As a result, the indu ctor’s magnetic field

collapses, generating a voltage that forces current from ground through the synchronous rectifier to t he 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 filt er capacitor stores charge when the inductor current is hig h, and releases it when low,

smoothing the voltage across the load. The output voltage is regulated by modulating the PFET swit ch on time to

control the average current sent to the load. The effect is identical to sending a duty-cycle modulated rect angular 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 out put down, the error amplifier output increases, which allows th e 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.)

AS1332

AGND PGND

VCON

PVIN VDD

1.3V to 3.16V

VOUT = 2.5 x VCON

4.7 µF

3.3 µH VOUT

2.7V to 5.5V

VIN

10 µF

DAC

ON/OFF

System

Controller

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AS1332

Datasheet - D et a i l e d De s c r i p t i o n

Internal Synchronous Rectifier

To redu ce the rectifier forward voltage drop and the associated power loss, the AS1332 uses an intern al 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 becau se 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 ad justable 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 vol tage of a PA appl ication 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 po wer 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 port able 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 (<0.5 V ) places the AS1332 in a 0.01µA (typ.) shutdown mode.

Thermal Overload Protection

To preve nt the AS1332 from short-term misuse and overload conditions th e chip includes a thermal overload

protection. To block the norma l 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 t hermal overload conditions may damage the device and is cons idered 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 swit ch 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 limi t mode is to prevent the device of the loss of the curren t cont rol.

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AS1332

Datasheet - App 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). Thi s feat ure eliminates the need for external fe edback 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 devic e.

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 - App 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 effi-

ciency and output current. Inductors with low core losses and small DCR at 2MHz are recommended.

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 f ootprints.

For input decoupling the ceramic capacitor should be located as close to the device as practical. A 4.7µF input capaci-

tor 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.

EN Pin Control

Drive the EN pin using the system controll er 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.

Table 6. Recommended Inductors

Part Number LDCR Current Rating Dimensions (L/W/T) Manufacturer

LPS4018-222ML_ 2.2µH 0.070Ω 2.9A 3.9x3.9x1.7mm Coilcraft

www.coilcraft.com

LPS4018-332ML_ 3.3µH 0.080Ω 2.4A 3.9x3.9x1.7mm

LPS4018-472ML_ 4.7µH 0.125Ω 1.9A 3.9x3.9x1.7mm

Table 7. Recommended Capacitors for the Step-Down Converter

Part Number CVoltage Type Size Manufacturer

GRM21BR60J226ME39 22µF 6.3V X5R 0805 Murata

www.murata.com

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 KEMET

www.kemet.com

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AS1332

Datasheet - App 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 swit ch turns on, the input

voltage is applied to the induct or, 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 lo ad, 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

PGND AGND

VCON

PVIN VDD

VOUT = 2.5 x VCON

4.7 µF

3.3 µH VOUT

2.7V to 5.5V

VIN

10 µF

C2 +

fOSC = 2MHz

0.52V to 1.27V

VCON

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AS1332

Datasheet - Pa ck ag e D ra wi ng s a nd Markings

10 Package Drawings and Markings

The device is available in a 8-pin WL-CSP

Figure 33. Package Drawings

1625 ±20µm

1515 ±20µm

Top through view Bottom view

(Ball side)

500 500

500

320 typ.

600 ±30µm

Notes:

ccc Coplanarity

All dimensions are in µm

40 typ. 240 typ.

40 µm

CCC

330 ±20

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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.

Note: All products are RoHS compliant and Pb-free.

Buy our products or get free samples online at ICdirect: http://www.austriamicrosystems.com/ICdirect

For further info rmation and requests, please contact us mailto:sales@austriamicrosystems.com

or find your local distribu tor at http://www.austriamicrosystems.com/distributor

Table 8. Ordering Information

Ordering Code Marking Description Delivery Form Package

AS1332-BWLT ASQW 650mA, DC-DC Step-Down for RF Tape and Reel 8-pi n WL-CSP

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AS1332

Datasheet

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