The TK654xx low power step-down converter is designed
for portable battery systems, capable of operating from a
single Li-ion battery cell or multiple alkaline or rechargeable
(NiCd or NiMH) battery cells (up to 6 V). The TK654xx
provides the power switch, synchronous rectifier, and the
control circuit for a buck step-down converter. Only two
external components are required to complete the stepdown conversion.
APPLICATIONS
■ Battery Powered Systems
■ Cellular Telephones
■ Pagers
■ Personal Communications Equipment
■ Radio Controlled Systems
■ Toys
Driving the SB pin low will disable the TK654xx and drop
the quiescent current on the input supply to approximately
18 µA.
Pulse Current Amplitude control is used to regulate the
voltage at the V
of the TK654xx drops below the regulation threshold, a
current pulse is transferred from the input supply to the
output. The TK654xx 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 TK654xx is available in a miniature 6-pin SOT23L-6
surface mount package.
pin of the IC. When the output voltage
OUT
TK654xxM
The TK654xx 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 200 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 1.22 V, the Low Battery
BLOCK DIAGRAM
Output (LBO) pin will become asserted. The dual-function
LBI pin can alternatively be used as a Standby (SB) pin.
V
IN
ORDERING INFORMATION
V
OUT
REF
LBI/SB
Voltage Code
VOLTAGE CODE
18 = 1.8 V
21 = 2.1 V
24 = 2.4 V
25 = 2.5 V
27 = 2.7 V
30 = 3.0 V
33 = 3.3 V
TK654xxM
Tape/Reel Code
TAPE/REEL CODE
TL: Tape Left
September 1999 TOKO, Inc. Page 1
CONTROL
CIRCUIT
BATTERY
MONITOR
SW
GND
LBOOFF
LBO
TK654xx
ADVANCED INFORMATION
ABSOLUTE MAXIMUM RATINGS
All Pins Except GND ............................................... 6.5 V
Power Dissipation (Note 1) ................................ 400 mW
Storage Temperature Range ................... -55 to +150 °C
Operating Temperature Range ...................-20 to +80 °C
Junction Temperature ...........................................150 °C
Lead Soldering Temperature (10 s.) .....................235 °C
TK654xx ELECTRICAL CHARACTERISTICS
Test conditions: VIN = 5 V, I
LOBMYSRETEMARAPSNOITIDNOCTSETNIMPYTXAMSTINU
= 1 mA, T
OUT
= TJ = Full Operating Temperature Range, unless otherwise specified.
A
V
V
∆V
∆V
I
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V
V
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V=
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C°52=751.122.1282.1V
C°52=751.122.1282.1V
)3etoN(,Am001ot0=54021Vm
)3etoN(,V6ot4=602Vm
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0105Aµ
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PORD
Note 1: Power dissipation is 400 mW when mounted as recommended. Derate at 3.2 mW/°C for operation above 25 °C. Power dissipation is 200
mW in Free Air. Derate at 1.6 mW/°C for operation above 25 °C
Note 2: V
Note 3: When using test circuit.
Note 4: When using test circuit and ramping VIN down.
Note 5: When using test circuit with SB pin resistors removed and tied to VIN. (VIN = 1.8 V)
Note 6: When using test circuit with SB pin resistors removed and tied to VIN. (VIN = 3.3 V)