ADM1051A データシートの表示（PDF） - Analog Devices
部品番号
コンポーネント説明
メーカー
ADM1051A Datasheet PDF : 10 Pages
| |||
ADM1051/ADM1051A
For compatibility with the TYPEDET signal, the regulator output
voltage of Channel 1 may be selected using the Shutdown pin.
This is a multilevel, dual-function input that allows selection of
the regulator output voltage as well as shutdown of the regulator.
By setting SHDN1 to different voltages, the regulator can be put
into four different operating modes.
Table I. Shutdown Functionality for 1.5 V Channel
SHDN1 Voltage
< 0.8 V
2 V–3.9 V
4.3 V–5.3 V
>6.2 V or Floating
Mode Function
1
Force Output Low, Regulator
Shutdown
2
1.5 V Output
3
Force Output High, VOUT = 3.3 V
4
1.5 V Output
If the SHDN1 pin is connected to a voltage less than 0.8 V, the
FORCE output will go low and the regulator will be shut down.
If the SHDN1 pin is connected to a voltage greater than 6.2 V,
or simply left open-circuit, the regulator will operate normally
and provide 1.5 V out. This allows the regulator to operate
normally with no external connection to SHDN1.
If the SHDN1 pin is connected to a voltage between 2 V and 3.9 V,
the regulator will also operate normally and provide 1.5 V out.
If the SHDN1 pin is connected to a voltage between 4.3 V and
5.3 V, the FORCE output will be high and the external MOSFET
will be turned hard on, making the output voltage equal to the 3.3 V
input (less any small drop due to the on-resistance of the MOSFET).
In this mode it is not actually regulating, but simply acting as a
switch for the 3.3 V supply. The voltage drop across the Channel 1
MOSFET in Mode 3 can be minimized by using a MOSFET
with very low on resistance, for which Channel 1 is optimized,
such as the PHD55N03LT.
The latter two modes allow the regulator to be controlled by the
TYPEDET signal simply by using potential divider, as shown in
Figure 2.
PC 5V SUPPLY
3k⍀
SHDN1
TYPEDET
3k⍀
Figure 2. Using SHDN1 with TYPEDET Signal
A shutdown function can be added by connecting an open-drain/
open-collector logic output to SHDN1, or by using a totem-pole
logic output with a Schottky diode, as shown in Figure 3.
PC 5V SUPPLY
COMPLEMENTARY
OR TOTEM-POLE
OUTPUT
3k⍀
EN
SCHOT T KY
DIODE
TYPEDET
3k⍀
SHDN1 ADM1051/
ADM1051A
PC 5V SUPPLY
OPEN-DRAIN OR
OPEN-COLLECTOR
OUTPUT
EN
TYPEDET
3k⍀
3k⍀
SHDN1 ADM1051/
ADM1051A
Figure 3. TYPEDET Voltage Selection Combined with
Shutdown Function
When the logic output is high or turned off, the regulator mode
will be controlled by TYPEDET. When the logic output is low,
the regulator will be shut down.
Table II. TYPEDET and Shutdown Truth Table
TYPEDET
EN
Regulator Mode
X
0
Shutdown
0
1
1.5 V
1
1
3.3 V
X = Don’t care.
Note that when Channel 1 of the ADM1051 is set to 3.3 V,
Channel 2 should not be shut down while Channel 1 is active.
12V SUPPLY
POR THRESHOLD
4V – 7V
VREF TURN-ON
THRESHOLD
3.3V SUPPLY
TO EXTERNAL
MOSFET DRAIN
GATE DRIVE TO
EXTERNAL
MOSFET
CHANNEL 1
OR CHANNEL 2
OUTPUT VOLTAGE
CHANNEL 1
OR CHANNEL 2
OUTPUT CURRENT
MOSFET GATE
THRESHOLD
NORMAL
OUTPUT VOLTAGE
OUTPUT < 0.8 ؋ VREG
HICCUP MODE
HOLD-OFF TIME
DEVICE ENTERS HICCUP MODE
FAULT CURRENT
2 AMPS
OFF ON
1:40 DUTY CYCLE
Figure 4. Power-On Reset and Hiccup Mode
REV. 0
–7–
FAULT
REMOVED
Share Link: 