UCC29421 Datasheet, PDF (1/35 Pages) Texas Instruments – Multimode High Frequency PWM Controller

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UCC29421, UCC29422, UCC39421, UCC39422
MULTIMODE HIGHĆFREQUENCY PWM CONTROLLER
SLUS246C − OCTOBER 1999 − REVISED FEBRUARY 2005
D Operation Down to an Input
Voltage of 1.8 V
simplified schematic block diagram and
application circuit
D High Efficiency Boost, SEPIC or
Flyback (Buck-Boost) Topologies
D Drives External FETs for
High-Current Applications
D Up to 2-MHz Oscillator
D Synchronizable Fixed Frequency
Operation
D High-Efficiency Low-Power Mode
D High-Efficiency at Very Low-Power
with Programmable Variable
Frequency Mode
D Pulse-by-Pulse Current Limit
D 5-µA Supply Current in Shutdown
D 150-µA Supply Current in Sleep
Mode
D Selectable NMOS or PMOS
Rectification
D Built-In Power-On Reset
(UCC39422 Only)
D Built-In Low-Voltage Detect
(UCC39422 Only)
description
SYNC/SD
13
RT
14
1.8 V(MIN)
1.24 V
VREF
PWM
OSC
VPUMP
7
VIN
9
CHARGE
PUMP
VPUMP
8 ^CP
3 ^VOUT
2 ^RSEN
RECT
4
ANTI−
CROSS
COND.
VGD
RSEL
19
CHRG
6
PWM CIRCUITRY
CURRENT LIMIT
LOW POWER
MODE
SLOPE
COMPENSATION
PFM MODE
CONTROL
GND
15
+
X10
ERROR ^{1.24 V}
AMP
+
ISENSE
12
PGND
5
FB
17
COMP
18
PFM
16
+
+ _{2 CELL}
ALKALINE/
+
NiCd OR
1 LI−ION
VOUT
50 mV TYP
The UCC39421 family of synchronous
RESET
PWM controllers is optimized to operate
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from dual alkaline/NiCd cells or a single
Lithium-Ion (Li-Ion) cell, and convert to
LOWBAT
adjustable output voltages from 2.5 V to
10
8 V. For applications where the input
voltage does not exceed the output, a
standard boost configuration is used.
200 mS
RESET/
POR
1.22V
UCC39422
ONLY
+
+
1.18 V
RSADJ
20
VDET
11
1.24 V
UDG−98122
For other applications where the input voltage can swing above and below the output, a 1:1 coupled inductor
(Flyback or SEPIC) is used in place of the single inductor. Fixed frequency operation can be programmed, or
synchronized to an external clock source. In applications where (at light loads) variable frequency mode is
acceptable, the IC can be programmed to automatically enter PFM (pulse frequency modulation) mode for an
additional efficiency benefit.
Synchronous rectification provides excellent efficiency at high power levels, where N- or P- type MOSFETs can
be used. At lower power levels (between 10% and 20% of full load) where fixed frequency operation is required,
low power mode is entered. This mode optimizes efficiency by cutting back on the gate drive of the charging
FET. At very low power levels, the IC enters a variable frequency mode (PFM). PFM can be disabled by the user.
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
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