Datasheet

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L6920

February 2005

1 Features

■ 0.6 TO 5.5V OPERATING INPUT VOLTAGE

■ 1V START UP INPUT VOLTAGE

■ INTERNAL SYNCHRONOUS RECTIFIER

■ ZERO SHUT DOWN CURRENT

■ 3.3V AND 5V FIXED OR ADJUSTABLE

OUTPUT VOLTAGE (2V UP TO 5.2V)

■ 120mΩ INTERNAL ACTIVE SWITCH

■ LOW BATTERY VOLTAGE DETECTION

■ REVERSE BATTERY PROTECTION

1.1 Applications

■ ONE TO THREE CELL BATTERY DEVICES

■ PDA AND HAND HELD INSTRUMENTS

■ CELLULAR PHONES - DIGITAL CORDLESS

PHONE

■ PAGERS

■ GPS

■ DIGITAL CAMERAS

2 Description

The L6920 is a high efficiency step-up controller re-

quiring only three external components to realize the

conversion from the battery voltage to the selected

output voltage.

The start up is guaranteed at 1V and the device is op-

erating down to 0.6V.

Internal synchronous rectifier is implemented with a

120m

Ω

P-channel MOSFET and, in order to improve

the efficiency, a variable frequency control is imple-

mented.

1V HIGH EFFICIENCY SYNCRONOUS STEP UP CONVERTER

Figure 1. Application Circuit

OUT

LBO

GND

SHDN

LBI

REF

OUT

2.5V 3.3V

500mA

L6920D

C3 C1

gure 1.

age

Table 1. Order Codes

Part Number Package

L6920D TSSOP8 Tube

L6920DTR Tape & Reel

TSSOP8

Rev. 2

Summary of content (13 pages)

PAGE 1
L6920 1V HIGH EFFICIENCY SYNCRONOUS STEP UP CONVERTER 1 ■ ■ ■ ■ ■ ■ ■ ■ Figure 1. Package Features 0.6 TO 5.5V OPERATING INPUT VOLTAGE 1V START UP INPUT VOLTAGE INTERNAL SYNCHRONOUS RECTIFIER ZERO SHUT DOWN CURRENT 3.3V AND 5V FIXED OR ADJUSTABLE OUTPUT VOLTAGE (2V UP TO 5.2V) 120mΩ INTERNAL ACTIVE SWITCH LOW BATTERY VOLTAGE DETECTION REVERSE BATTERY PROTECTION TSSOP8 Table 1. Order Codes 2 1.
PAGE 2
L6920 Table 1. Pin Description Pin Name Function 1 FB Output voltage selector. Connect FB to GND for Vout=5V or to OUT for Vout=3.3V. Connect FB to an external resistor divider for adjustable output voltage (from 2V to 5.2V) [see R4 and R5, fig. 7]. 2 LBI Battery low voltage detector input. The internal threshold is set to 1.23V. A resistor divider is needed to adjust the desired low battery threshold: R1 V LBI = 1.23V ⋅ ⎛ 1 + --------⎞ [see R1 and R2, fig.
PAGE 3
L6920 Table 4. Electrical Characteristcs (Vin = 2V, FB = GND, Tamb = -40°C to 85°C and Tj < 125°C unless otherwise specified) Symbol Parameter Test Condition Min. Typ. Max. Unit VCC SECTION Vin Minimum operating Input Voltage Vin Minimum Start Up Input Voltage Iq Quiescent Current 0.6 V 1 V Il =0 mA, FB = 1.4V, Vout = 3.3V LBI = SHDN = 2V, Tj = Tamb 9 15 µA Il =0 mA, FB = 1.4V, Vout = 5V LBI = SHDN = 2V, Tj = Tamb 11 18 µA Isd Shut Down Current Vin = 5V, Il =0 mA 0.
PAGE 4
L6920 Figure 3. Efficiency vs. Output Current Figure 5. Startup Voltage vs Output Current 1.4 100 Vin = 2.4V 90 1.2 80 Vin = 1.2V 1 Startup voltage (V) EFFICIENCY η [%] 70 60 50 40 30 Vout = 3.3V L = 47µH C = 100µF 20 0.8 0.6 0.4 10 L = 47µH C = 22µF 0.2 0 0.01 0.1 1 10 100 1000 LOAD CURRENT [mA] 0 30 100 Vin = 3.6V 90 Vin = 2.4V 80 Vin = 1.2V EFFICIENCY η [%] 70 60 50 f Vout = 5V L = 47µH C = 100µF 40 30 20 10 0 0.01 0.
PAGE 5
L6920 3 Detailed Description The L6920 is a high efficiency, low voltage step-up DC/DC converter particularly suitable for 1 to 3 cells (Li-Ion/ polymer, NiMH respectively) battery up conversion. These performances are achieved via a strong reduction of quiescent current (10µA only) and adopting a synchronous rectification, that implies also a reduced cost in the application (no external diode required).
PAGE 6
L6920 Figure 7. PFM mode Condition: Vout = 5V; Vin =1.5V. Trace1: Vout (50mV~/div) Trace 4: IL (100mA/div) Time div.: 5µs/div Figure 9. Heavy load - Inductor current ripples below Ilim Trace1: Vout (100mV~/div) Trace 4: IL (200mA/div) Time div.: 20 µs/div Figure 8. Heavier load - Train pulses overlapping. Trace1: Vout (100mV~/div) Trace 4: IL (200mA/div) Time div.: 10 µs/div Figure 10. Heavy load and High ESR. Regulation falls in continuous mode of operation.
PAGE 7
L6920 Figure 11. No regulation. Iload > Iload_lim Trace1: Vout (100mV~/div) Trace 4: IL (200mA/div). Time div.: 5 µs/div The synchronous switch body diode causes a parasitic path between power supply and output that can't be avoided also in shutdown. 4.3 Low battery detection The L6920 includes a low battery detector comparator. Threshold is VREF voltage and a 1.3% hysteresis is added to avoid oscillations when input crosses the threshold slowly.
PAGE 8
L6920 Figure 12. Demoboard Circuit Panasonic ELL6RH100M +VBATT VBATT R1 N.C. LBI C2 47µF 7 GND 8 C4 100nF 4 6 1 F.B. VOUT VOUT 5 C1 47µF C3 N.C. R3 N.C. L6920 3 GND Panasonic EEFCDJ470R 2 R2 N.C. VREF +VBATT L1 10µH Panasonic EEFCDJ470R GND LBO LBO SHDN J1 1 2 3 SHDN 1 R4 N.C. 3 R5 N.C. 2 J2 not mounted components D01IN1310 Table 6. Jumper Position Function 1-2 Device enabled 2-3 Device disabled J1 None J2 Adjustable using R4 and R5 [not mounted] 1-2 3.
PAGE 9
L6920 Table 7. Capacitors distributors main list Manufacturer Series Cap Value (µF) Rated Voltage (V) ESR (mΩ) AVX TPS 15 to 470 6.3 50 to 1500 KEMET T510/T494/ T495 10 to 470 6 30 to 1000 PANASONIC EEFCD 22 to 47 6.3 50 to 700 SANYO POSCAP TPA/B/C 22 to 230 6.3 40 to 80 SPRAGUE 595D 100 to 390 6.3 160 to 700 5.3 Inductor selection Usually, inductors ranging between 5µH to 40µH satisfy most of the applications.
PAGE 10
L6920 Figure 13. Demoboard Components (Top side). 4.5cm 4cm Figure 14. Demoboard Layout (Top side). 4.5cm 4cm Figure 15. Demoboard Layout (Bottom side). 4.
PAGE 11
L6920 6 Package Information Figure 16. TSSOP8 Mechanical Data & Package Dimensions mm inch DIM. MIN. TYP. A MAX. MIN. TYP. 1.20 A1 0.050 A2 0.800 b MAX. 0.047 0.150 0.002 1.050 0.031 0.190 0.300 0.007 0.012 c 0.090 0.200 0.003 0.008 D (1) 2.900 3.000 3.100 0.114 0.118 0.122 E 6.200 6.400 6.650 0.244 0.252 0.260 E1 (1) 4.300 4.400 4.500 0.169 0.173 0.177 e L L1 k aaa 1.000 0.650 0.450 0.600 OUTLINE AND MECHANICAL DATA 0.006 0.039 0.041 0.026 0.750 0.
PAGE 12
L6920 7 Revision History Table 9. Revision History Date Revision May 2003 1 First Issue. February 2005 2 Modified the max. value of the Isd parameter in the Table 4 pag. 3.
PAGE 13
L6920 Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication are subject to change without notice.