ACT6330
Rev0, 02-Apr-08
STEP-UP DC/DC CONVERTER (REG2)
nent, choice can be optimized to achieve minimum
total solution size in applications that require the
smallest possible footprint, or can be optimized to
achieve the highest possible efficiency.
FUNCTIONAL DESCRIPTION
General Description
REG2 is a highly efficient step-up DC/DC converter
that employs a fixed frequency, current-mode,
PWM architecture. This regulator is optimized for
use in a wide range of applications including gen-
eration constant voltage of up to 20V.
Figure 1:
REG2 Startup Waveform into no load
CH2
CH1
Over-Voltage Protection
REG2 features internal over-voltage protection
(OVP) circuitry which protects the system from fault
conditions. The ACT6330’s OVP threshold is set at
22V, and if necessary, regulates the output voltage
to ensure that it never exceeds this voltage.
ACT6330 requires a 10kꢀ resistor connected from
output capacitor to OVP2 pin.
CH1: VON2, 2V/div
CH2: VOUT2, 5V/div
TIME: 250µs/div
Figure 2:
Thermal Protection
REG2 Startup Waveform into full load
The Thermal shutdown protection prevents exces-
sive thermal stress, please refer to Thermal Shut-
down Protection for more information.
CH2
CH1
Enabling and Disabling REG2
REG2 is enabled or disabled using ON2. Drive ON2
to a logic-high to enable REG2. Drive ON2 to a
logic-low to disable REG2, reducing supply current
to less than 1µA. As with all non-synchronous step-
up DC/DC converter, REG2’s application circuit pro-
cedures a DC current path between the input and
the output in shutdown mode. It is important to con-
sider the effect that this may have in your applica-
tion.
CH1: VON2, 2V/div
CH2: VOUT2, 5V/div
TIME: 250µs/div
Output Voltage Selection
Figure 3 shows the feedback network necessary to
set the output voltage when using the adjustable
voltage option. Select components as follows: Set
Soft-start
REG2 includes soft-start circuitry. When enabled,
the output voltage of REG2 tracks an internal 80µs
soft-start ramp.
R
FB2 = 51kꢀ, then caculate RFB1 using the following
equation:
⎛
⎞
RFB1
RFB2
⎜
⎟
⎟
VOUT2 =VFB2 1+
(1)
As seen in Figure 1 and Figure 2, the output tracks
the internal soft-start ramp and powers up in a
monotonic maner that is independent of loading.
This circuitry ensures that the output powers up in a
controlled maner, greatly simplifying power turn-on
design considerations.
⎜
⎝
⎠
Where VFB2 is 1.25V.
Figure 3:
Output Voltage Setting
VOUT2
Compensation and Stability
REG2 utilizes current-mode control and an internal
compensation network to optimize transient per-
formance, ease compensation, and improve stabil-
ity over a wide range of operating conditions. REG2
is a flexible regulator, and with just a simple compo-
RFB1
ACT6330
FB2
RFB2
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