TK65025
STEP-UP VOLTAGE CONVERTER WITH VOLTAGE MONITOR
FEATURES
s
Guaranteed 0.9 V Operation
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Very Low Quiescent Current
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Internal Bandgap Reference
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High Efficiency MOS Switching
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Low Output Ripple
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Microprocessor Reset Output
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Laser-Trimmed Output Voltage
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Laser-Trimmed Oscillator
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Undervoltage Lockout
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Regulation by Pulse Burst Modulation (PBM)
APPLICATIONS
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Battery Powered Systems
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Cellular Telephones
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Pagers
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Personal Communications Equipment
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Portable Instrumentation
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Portable Consumer Equipment
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Radio Control Systems
DESCRIPTION
The TK65025 Low Power Step-Up DC-DC converter is
designed for portable battery-powered systems, capable
of operating from a single battery cell down to 0.9 V. The
TK65025 provides the power switch and the control circuit
for a boost converter. The converter takes a DC input and
boosts it up to 3 volts. This regulated 3 volt output is
typically used to supply power to a microprocessor-con-
trolled system.
The output voltage is laser-trimmed to 3.0 V. An
internal detector monitors the output voltage and provides
an active-low microprocessor reset signal whenever the
output voltage falls below an internally preset limit. An
internal undervoltage lockout circuit is utilized to prevent
the inductor switch from remaining in the "ON" mode when
the battery voltage is too low to permit normal operation.
Pulse burst modulation (PBM) is used to regulate the
voltage at the V
OUT
pin at the IC. PBM is the process in
which an oscillator signal is gated or not gated to the switch
drive each period. The decision is made just before the
start of each cycle and is based on comparing the output
voltage to an internally-generated bandgap reference. The
decision is latched, so the duty ratio is not modulated within
a cycle. The average duty ratio is effectively modulated by
the "bursting" and skipping of pulses which can be seen at
the IND pin of the IC. Special care has been taken to
achieve high reliability through the use of Oxide, double
Nitride passivation. The TK65025 is available in a very
small plastic surface mount package. (SOT-23L)
Customized levels of accuracy in oscillator frequency
and output voltage are available.
2
TK65025M
VIN 1
5
M2
6 RESET
5 GND
4 VOUT
GND 2
IND 3
BLOCK DIAGRAM
IND
3
V OUT
4
ORDERING INFORMATION
TK65025M
V IN
Tape/Reel Code
1
V
REF
CONTROL
CIRCUIT
RC OSC.
2,5
UVLO
6
RESET
TAPE/REEL CODE
BX : Bulk/Bag
TL : Tape Left
GND
February, 1997 Toko, Inc.
Page 1
TOKO [ TOKO, INC ]
