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December 2011 Doc ID 9302 Rev 10 1/16

L6926

High efficiency monolithic synchronous step down regulator

Features

■ 2 V to 5.5 V battery input range

■ High efficiency: up to 95%

■ Internal synchronous switch

■ No external Schottky required

■ Extremely low quiescent current

■ 1 mA max shutdown supply current

■ 800 mA max output current

■ Adjustable output voltage from 0.6 V

■ Low drop-out operation: up to 100% duty cycle

■ Selectable low noise/low consumption mode at

light load

■ Power Good signal

■ ± 1% output voltage accuracy

■ Current-mode control

■ 600 kHz switching frequency

■ Externally synchronizable from 500 kHz to 1.4

MHz

■ OVP

■ Short-circuit protection

Applications

■ Battery-powered equipment

■ Portable instruments

■ Cellular phones

■ PDAs and hand held terminals

■ DSC

■ GPS

Description

The device is DC-DC monolithic regulator

specifically designed to provide extremely high

efficiency. L6926 supply voltage can be as low as

2 V allowing its use in single Li-ion cell supplied

applications. Output voltage can be selected by

an external divider down to 0.6 V. Duty cycle can

saturate to 100% allowing low dropout operation.

The device is based on a 600 kHz fixed-

frequency, current mode-architecture. Low

consumption mode operation can be selected at

light load conditions, allowing switching losses to

be reduced. L6926 is externally synchronizable

with a clock which makes it useful in noise-

sensitive applications. Other features like power-

good, overvoltage protection, short-circuit

protection and thermal shutdown (150 °C) are

also present.

VFQFPN8

MSOP8

(3x3x1.0 mm)

Figure 1. Application test circuit

AM10472v1

= 2 to 5.5 V

= 1.8V

10µF

6.3V

100k

500k

200k

L 6.8 µH

10µF

6.3V

220pF

10k

PGOOD

VFB

GNDCOMP

RUN

SYNC

www.st.com

Summary of content (16 pages)

PAGE 1
L6926 High efficiency monolithic synchronous step down regulator Features ■ 2 V to 5.5 V battery input range ■ High efficiency: up to 95% ■ Internal synchronous switch ■ No external Schottky required ■ Extremely low quiescent current ■ 1 mA max shutdown supply current ■ 800 mA max output current ■ Adjustable output voltage from 0.
PAGE 2
Contents L6926 Contents 1 Pin settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4 Operation description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4.1 5 Modes of operation . . . . . . . . . .
PAGE 3
L6926 1 Pin settings Pin settings Figure 2. Pin connection (top view) RUN 1 8 PGOOD COMP 2 7 SYNC VFB 3 6 VCC GND 4 5 LX D01IN1239AMOD RUN 1 COMP 2 8 PGOOD 7 SYNC E-pad VFB 3 6 VCC GND 4 5 LX AM10471v1 Table 1. Pin description Pin n° Name 1 RUN 2 COMP Error amplifier output. A compensation network has to be connected to this pin. Usually a 220 pF capacitor is enough to guarantee the loop stability. 3 VFB Error amplifier inverting input.
PAGE 4
Maximum ratings 2 L6926 Maximum ratings Table 2. Absolute maximum ratings Symbol Value Unit V6 Input voltage -0.3 to 6 V V5 Output switching voltage -1 to VCC V V1 Shutdown -0.3 to VCC V V3 Feedback voltage -0.3 to VCC V V2 Error amplifier output voltage -0.3 to VCC V V8 PGOOD -0.3 to VCC V V7 Synchronization mode selector -0.3 to VCC V PTOT Power dissipation at TA = 70 °C 0.
PAGE 5
L6926 3 Electrical characteristics Electrical characteristics TJ = 25 °C, VIN = 3.6 V unless otherwise specified. Table 4. Electrical characteristics (1) Symbol Vcc Parameter Test condition Operating input voltage Vcc ON Turn on threshold Vcc OFF Turn off threshold Vcc hys Hysteresis After turn on Min. (1) Typ. 2 High side Ron Rn Low side Ron Vcc = 3.6 V, Ilx =100 mA (1) Vcc = 3.6 V, Ilx =100 mA (1) Vcc = 3.6 V (1) Vcc = 3.
PAGE 6
Electrical characteristics Table 4. L6926 Electrical characteristics (1) (continued) Symbol Parameter Test condition Min. Typ. Max. Unit 1.3 V Run Vrun_H RUN threshold high Vrun_L RUN threshold low Irun RUN input current 0.4 (2) V 25 nA SYNC/MODE function Vsync_H Sync mode threshold high Vsync_L Sync mode threshold low 1.3 0.
PAGE 7
L6926 4 Operation description Operation description The main loop uses slope compensated PWM current mode architecture. Each cycle the high side MOSFET is turned on, triggered by the oscillator, so that the current flowing through it (the same as the inductor current) increases.
PAGE 8
Operation description 4.1.1 L6926 Low consumption mode In this mode of operation, at light load, the device operates discontinuously based on the COMP pin voltage, in order to keep the efficiency very high also in these conditions. While the device is not switching the load discharges the output capacitor and the output voltage goes down. When the feedback voltage goes lower than the internal reference, the COMP pin voltage increases and when an internal threshold is reached, the device starts to switch.
PAGE 9
L6926 Operation description current limit, the high side MOSFET turns off and so the TON is reduced down to the minimum value (250 ns typ.) in order to reduce as much as possible ΔION. Anyway, if VOUT is low enough it can be that the inductor peak current further increases because during the TOFF the current decays very slowly. Due to this reason a second protection that fixes the maximum inductor valley current has been introduced.
PAGE 10
Additional features and protections L6926 5 Additional features and protections 5.1 DROPOUT operation The Li-Ion battery voltage ranges from approximately 3 V and 4.1 V - 4.2 V (depending on the anode material). In case the regulated output voltage is from 2.5 V and 3.3 V, it can be that, close to the end of the battery life, the battery voltage goes down to the regulated one.
PAGE 11
L6926 6 Package mechanical data Package mechanical data In order to meet environmental requirements, ST offers these devices in different grades of ECOPACK® packages, depending on their level of environmental compliance. ECOPACK® specifications, grade definitions and product status are available at: www.st.com. ECOPACK® is an ST trademark. Table 5. MSOP8 mechanical data mm. Dim. Min. Typ. A Max. 1.10 A1 0 A2 0.75 b 0.22 0.40 c 0.08 0.23 (1) D E E1 (1) 0.85 3.00 3.20 4.65 4.90 5.
PAGE 12
Package mechanical data Figure 4.
PAGE 13
L6926 Package mechanical data mm inch DIM. MIN. TYP. MAX. 0.80 0.90 1.00 0.0315 0.0354 0.0394 A1 0.02 0.05 0.0008 0.0020 A2 0.70 0.0276 A3 0.20 0.0079 A b 0.18 D D2 2.23 2.38 1.49 1.64 2.48 0.40 MAX. OUTLINE AND MECHANICAL DATA 0.0071 0.0091 0.0118 0.0878 0.0937 0.0976 0.1181 1.74 0.50 0.30 TYP. 0.1181 3.00 e L 0.30 3.00 E E2 0.23 MIN. 0.0587 0.0646 0.0685 0.0197 0.50 0.0118 0.0157 0.0197 VFQFPN8 (3x3x1.
PAGE 14
Order codes 7 Order codes Table 6.
PAGE 15
L6926 8 Revision history Revision history Table 7. Document revision history Date Revision Changes Jan-2004 2 First Issue in EDOCS. Sep-2004 3 Changed the style look and feel. Add. new package VFSON8. Add. V8 and V7 parameter in the Table 2 - Absolute Maximum Ratings. Nov-2004 4 Update order codes Sep-2005 5 Updated Table. 5 electrical characteristics. Nov-2005 6 Added VFQFPN8 package and new part numbers. 27-Oct-2006 7 Added RthJA for VFQFPN8 in Table 3.
PAGE 16
L6926 Please Read Carefully: Information in this document is provided solely in connection with ST products. STMicroelectronics NV and its subsidiaries (“ST”) reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described herein at any time, without notice. All ST products are sold pursuant to ST’s terms and conditions of sale.