Datasheet

PGND
Sw1 Sw2
P1
P2
Control Logic
Switch
buffer
Switch
buffer
PV
IN
Buffer
Soft
Start
Ramp
Generator
FB
+
-
VREF
2 MHz
Oscillator
PFM
Generator
SYNC/
MODE
EN
SGND
VOUT
PFM_hi
PFM_low
NC
VDD
Error
Amp
VSEL
PWM
Comparator
N1
N2
LM3668
SNVS449M –JUNE 2007–REVISED MAY 2013 www.ti.com
DESCRIPTION (CONTINUED)
The LM3668 has 2 N-channel MOSFETS and 2 P-channel MOSFETS arranged in a topology that provides
continuous operation through the buck and boost operating modes. There is a MODE pin that allows the user to
choose between an intelligent automatic PFM-PWM mode operation and forced PWM operation. During PWM
mode, a fixed-frequency 2.2 MHz (typ.) is used. PWM mode drives load up to 1A. Hysteretic PFM mode extends
the battery life through reduction of the quiescent current to 45 µA (typ.) at light loads during system standby.
Internal synchronous rectification provides high efficiency. In shutdown mode (Enable pin pulled low) the device
turns off and reduces battery consumption to 0.01µA (typ.).
The LM3668 is available in a 12-pin WSON package. A high switching frequency of 2.2 MHz (typ.) allows the use
of tiny surface-mount components including a 2.2 µH inductor, a 10 µF input capacitor, and a 22 µF output
capacitor.
Functional Block Diagram
Figure 3. Functional Block Diagram
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