January 1999 TOKO, Inc. Page 1
TK653xx
ADVANCED INFORMATION
V
OUT
V
IN
LBO
LBI/SB
SW
CONTROL
CIRCUIT
BATTERY
MONITOR
REF
LBOOFF
PGND
GND
PV
IN
The TK653xx mid power step-down converter is designed
for portable battery powered systems, capable of operating
from single Li-ion battery cells or two NiCad battery cells.
The TK653xx provides the power switch, synchronous
rectifier, and the control circuit for a buck step-down
converter. Only three external components are required to
complete the step-down conversion.
The TK653xx provides laser-trimmed output voltages
ranging from 1.8 V to 3.3 V. The low resistance MOSFET
switch and synchronous rectifier allow average currents
up to 800 mA, while maintaining peak efficiencies up to
95%. A low-battery threshold and turn-off threshold can be
individually programmed by the user, utilizing a single
resistor divider connected to the Low Battery Input (LBI)
pin. When the resistively-divided supply voltage on the LBI
pin drops below approximately 1.25 V, the Low Battery
Output (LBO) pin will become asserted. The dual-function
LBI pin can alternatively be used as a Standby (SB) pin.
Driving the SB pin low will disable the TK653xx and drop
the quiescent current on the input supply to approximately
10 µA.
Pulse Burst Modulation (PBM) is used to regulate the
voltage at the V
OUT
pin of the IC. When the output voltage
of the TK653xx drops below the regulation threshold, a
current pulse is transferred from the input supply to the
FEATURES
■ Very Low Quiescent Current (10 µA)
■ Extremely Low Operating Current (25 µA)
■ Internal Battery Monitor
■ Regulates Down to 1.8 V
■ Short Circuit Protection
■ Synchronous Rectification
■ Up To 95% Efficient
BLOCK DIAGRAM
TK653xxM
LBO
V
IN
SW
GND
LBI/SB
V
OUT
PGND
PV
IN
ORDERING INFORMATION
TAPE/REEL CODE
TL: Tape Left
Tape/Reel Code
TK653xxM
VOLTAGE CODE
Voltage Code
ADVANCED
INFORMATION
APPLICATIONS
■ Battery Powered System
■ Cellular Telephones
■ Pagers
■ Personal Communications Equipment
■ Radio Controlled Systems
■ Toys
output. The TK653xx utilizes a proprietary control scheme,
where the average amplitude of the current pulse is varied
depending upon the current loads. The proprietary
architecture allows fast transient response and minimal
ripple while maintaining ease-of-use and low component
count.
The TK653xx is available in SOP-8 and DIP-8 packages.
DESCRIPTION
HIGH CURRENT STEP-UP CONVERTER WITH
BATTERY MONITOR