Datasheet
THEORY OF OPERATION
PEAK CURRENT REDUCTION
OFF SWITCHED
Step-Down(Buck)Mode
OFF ON
C
PUMP
Q
1
Q
3
Q
2
Q
4
C
IN
C
OUT
V
OUT
V
IN
Step-Up(Boost)Mode
(A) (B)
OFF
ON
ON
OFF
C
PUMP
Q
2
Q
4
C
OUT
V
OUT
C
PUMP
Q
2
Q
4
C
OUT
V
OUT
OFF
ON
Q
1
Q
3
ON
OFF
Q
1
Q
3
C
IN
V
IN
C
IN
V
IN
REG710
SBAS221G – DECEMBER 2001 – REVISED JANUARY 2009 ...........................................................................................................................................
www.ti.com
During the second half cycle the FET switched are
The REG710 regulated charge pump provides a
configured as shown in Figure 19 B, and the voltage
regulated output voltage for input voltages ranging
on C
PUMP
is added to V
IN
. The output voltage is
from less than the output to greater than the output.
regulated by skipping clock cycles as necessary.
This is accomplished by automatic mode switching
within the device. When the input voltage is greater
than the required output, the unit functions as a
variable frequency switch-mode regulator. This
In normal operation, the charging of the pump and
operation is shown in Figure 18 . Transistors Q
1
and
output capacitors usually leads to relatively high peak
Q
3
are held off, Q
4
is on, and Q
2
is switched as
input currents which can be much higher than that of
needed to maintain a regulated output voltage.
the average load current. The regulator incorporates
circuitry to limit the input peak current, lowering the
When the input voltage is less than the required
total EMI production of the device and lowering
output voltage, the device switches to a step-up or
output voltage ripple and input current ripple. Input
boost mode of operation, as shown in Figure 19 .
capacitor (C
IN
) supplies most of the charge required
A conversion clock of 50% duty cycle is generated. by input current peaks.
During the first half cycle the FET switches are
configured as shown in Figure 19 A, and C
PUMP
charges to V
IN
.
Figure 18. Simplified Schematic of the REG710 Operating in the Step-Down Mode
Figure 19. Simplified Schematic of the REG710 Operating in the Step-Up or Boost Mode
8 Submit Documentation Feedback Copyright © 2001 – 2009, Texas Instruments Incorporated
Product Folder Link(s): REG710