Richtek RT8238A, Manual

Page: 5 / 15

RT8238A
5
RT8238A-07 January 2014 www.richtek.com
© Copyright 2014 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation.
(V
CC
= 5V, V
IN
= 15V, V
EN
= 5V, V
MODE
= 5V, R
TON
= 500k Ω , T
A
= 25 ° C, unless otherwise specified)
Electrical Characteristics
Parameter Symbol Test Conditions Min Typ Max Unit
PWM Controller
V
CC
Quiescent Supply Current I
Q
FB forced above the regulation
point, V
EN
= 5V
-- 0.5 1.25 mA
V
CC
Shutdown Current I
SHDN
V
CC
Current, V
EN
= 0V
-- -- 1
μ
A
TON Operating Current
R
TON
= 500k
Ω -- 30 -- μ
A
TON Shutdown Current R
TON
= 500k
Ω
-- -- 1
μ
A
CS Shutdown Current CS pull to GND -- -- 1
μ
A
FB Error Comparator
Threshold Voltage
V
CC
= 4.5 o 5.5V, DEM 495 500 505 mV
FB Input Bias Current V
FB
= 0.5V
−
1 0.1 1
μ
A
Output Voltage Range 0.5 -- 3.3 V
On-Time
V
IN
=15V, V
PHASE
= 1.25V,
V
MODE
= 0V
267 334 401 ns
Minimum Off-Time
V
MODE
= 0V, FB = 0.45V
250 400 550 ns
Current Sensing Threshold
CS Source Current V
CS
= 0.5V to 2V 9 10 11
μ
A
CS Source Current TC On the basis of 25
°
C -- 4700 -- ppm/
°
C
Zero Crossing Threshold V
MODE
>1.8V, Phase
−
GND
−
10 -- 5 mV
ASM Min Frequency
V
MODE
= 2.5V
-- 25 -- kHz
Protection Function
Current Limit Threshold GND
−
PHASE, V
CS
= 1V 85 100 115 mV
UVP Threshold UVP Detect, FB Falling Edge 60 70 80 %
OVP Threshold OVP Detect, FB Rising Edge 120 125 130 %
OV Fault Delay FB forced above OV threshold -- 5 --
μ
s
V
CC
Power On Reset (POR)
Threshold
Rising Edge 3.7 3.9 4.2 V
POR Threshold Hysteresis -- 100 -- mV
Current Limit Ramp at Soft
Start
Enable to current limit threshold =
50mV
-- 900 --
μ
s
UV Blank Time From EN signal going high -- 4.5 -- ms
Thermal Shutdown
T
SD
-- 150 --
°
C
Thermal Shutdown Hysteresis
Δ
T
SD
-- 10 --
°
C
Driver On-Resistance
UGATE Driver Source
R
UGATEsr
BOOT
−
PHASE forced to 5V,
UGATE High State
-- 2.5 5 Ω
UGATE Driver Sink R
UGATEsk
BOOT
−
PHASE forced to 5V,
UGATE Low State
-- 1.5 3
Ω
LGATE Driver Source R
LGATEsr
LGATE High State -- 2.5 5
Ω
LGATE Driver Sink R
LGATEsk
LGATE Low State -- 0.8 1.5
Ω